University of Ghana http://ugspace.ug.edu.gh INCREASING WATER PRODUCTIVITY OF IRRIGATED RICE THROUGH VARYING NITROGEN AND MANAGEMENT METHODS BY ABDULAI YAKUBU (10508159) THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MPHIL CROP SCIENCE DEGREE. COLLEGE OF BASIC AND APPLIED SCIENCES CROP SCIENCE DEPARTMENT UNIVERSITY OF GHANA LEGON JULY, 2016 1 University of Ghana http://ugspace.ug.edu.gh DECLARATION In exception of references to the works of researchers which have been duly cited, this thesis is the result of my own work produced from research undertaken under supervision. ………………………..……… ………..………………… Abdulai Yakubu Date (Student) …………………………………. ………………………….. Dr. Joseph Ofori Date (Principal Supervisor) …………………………............. ...………………………... Dr. Mrs. Christiana Amoatey Date (Co-supervisor) i University of Ghana http://ugspace.ug.edu.gh DEDICATION I dedicate this work to my late father, Adamu Abdulai ii University of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGEMENTS First and foremost, I would like express my deepest sense of gratitude, endless praises and thanks to the Almighty Allah for helping me get this far on the academic ladder. Many people have been of immeasurable support to me since I commenced this study. In a special and grateful way, I wish to express my most profound gratitude to my supervisors; Dr. Joseph Ofori and Dr. Mrs. Christiana Amoatey. I would like to sincerely thank them for their patience and understanding and their constructive criticism, corrections and significant contributions on my write-ups. May Almighty Allah grant you His grace and peace! I want to acknowledge the Office of Research, Innovation and Development (ORID) for its sponsorship which has been of immense help in the way of funding both the field work and laboratory analysis. I’m also thankful to all the staff and people of Soil and Irrigation Research Centre (SIREC), Kpong especially, Joseph Nii Kotey Wristberg, Mr. Mensah, Kwabena Manu Agyei, Bright Salah Freduah, Sammuel Godson-Amamoo, and Benyamin Ofori for their corporation and assistance during the entire study period. I am grateful to my colleague, Dominic Kwadwo Anning for his assistance with data collection and laboratory procedures. I would like to express my deepest reverence to all lecturers and workers of Crop Science Department of University of Ghana for the valuable teaching, co-operation and inspirations throughout the course of this study and research work. The author wish to express his cordial thanks to Dr. J. O. Honger and Dr. Stephen Narh for their active help during the experimental period. Mr. Victor Adusei Okrah is gratefully acknowledged for giving me laboratory space and iii University of Ghana http://ugspace.ug.edu.gh all the necessary assistance for my laboratory procedures in the University of Ghana Soil Science Laboratory. My friends, Seidu Sumaila, Sulemana Amina, Mohammed Shiraz-deen and Yussif Haruna are also thanked for their company and help. I would like to thank the following course mates and colleagues for their support in many ways: Abdul Rahman Fahad, Baaba Hassan Taahir Namaa, Ibrahim Mohammed, Muzzammil Amin Bamba, Kyereh Dennis, Anthonio Frederick Amin, Ayarna Alex Williams, Nketiah Victor, Mathieu A.T. Ayenan, Owiredu-Gyamera Kwaku, Michael Akomoah-Boateng, Ablormeti Fred Kormla and Edmund Acquah. My friend Mahama Tahiru and his brother, Yakubu Abdul-Karim are thanked for being materially, financially and morally supportive to me. I appreciate the companionship and support of my fellow Gonjaland students who pursued various undergraduate and graduate programs at University of Ghana: Abdul Kadir Asumah, Bii Kipo, Ishmael Imoro, Seidu Mahama Awusi, and Seidu Mumuni Kamagtey. Over and above all, I would like to recognize and thank my brothers; Abdulai Abubakar Justice, Abdulai Enusah, Adamu Abdulai Baba, Wakawakawura Nugbaso, Abdulai Sulemana, Adamu Abdulai Kassim, Abdulai Yussif Mallam, Adamu Abdulai Mohammed, Abdulai Ibrahim and Abdulai Al-hassan and my sisters; Abdulai Memuna, Abdulai Mariama, Abdulai Masata, Abdulai Fatima and Abdulai Salamatu for their company and continual support during my graduate program. I would like to give special thanks to my mum, Hajia Fatima Lulasum, my step mum Hajia Aberewa, my nephews, nieces, uncles, aunts and cousins who have always encouraged and sustained my urge for higher academic accomplishment and professional advancement through their prayers, advice and inspiration. iv University of Ghana http://ugspace.ug.edu.gh ABSTRACT Globally, rice (Oryza sativa L.) is the third largest cultivated cereal crop with about 79 million hectares of irrigated lowlands providing 75% of the world’s rice production. Its productivity depends on many factors including Nitrogen (N) fertilizer and water management. This study was conducted to determine the effect of water management and N fertilizer on growth and yield of rice. The study also sought to evaluate the cost effectiveness of water use under various water management methods. To achieve the set objectives, pot and field experiments were conducted at Soil and Irrigation Research Centre (SIREC), Kpong between July, 2015 and January, 2016. The pot experiment was designed as randomized complete block (RCBD) in factorial arrangement of three water management treatments namely; continuous submergence (submerged), alternate wet and dry (AWD) and moist soil condition (moist) and three nitrogen fertilizer rates; no N fertilizer (N0), 60 kg N/ha (N1) and 90 kg N/ha (N2). In the field experiment, a split plot design with water management treatments as main plot and the three N-fertilizer treatments as subplots was used. Data including tiller numbers, leaf area index, above biomass accumulation, leaf chlorophyll content, days to 50% flowering, grains/panicles, panicles/m2, 1000 grain weight, grain yield and harvest index were collected. In addition, data on water use, water productivity, nitrogen uptake, nitrogen use efficiency, cost and benefit analysis were also recorded. Results obtained from both experiments revealed that, plant growth, yield and yield parameters were significantly influenced by water management and N fertilizer and their interaction except 1000 grain weight and days to 50% flowering. Analysis of variance further revealed that plant growth and yields were at par in AWD and submerged but yields were lower (3.4 t/ha) in moist treatment. N fertilizer had positive effect on rice growth and yields with higher yields (5.8 t/ha) observed when plants were treated with 90 N kg/ha. The interaction effect of submerged with 90 kg/ha N gave the highest grain yield v University of Ghana http://ugspace.ug.edu.gh (6.5 t/ha). For both pot and field experiments, N fertilizer effect on N uptake, water use and water productivity was ranked as N2 > N1 > N0. N uptake was found to be higher in AWD than moist but was at par with submerged treatment. Water management effect on water use and water productivity was ranked in this order: Submerged > AWD > Moist and Moist > AWD > Submerged respectively. AWD treatment had the highest net profit (9341.7 GH₵/ha) and thus making it most cost effective water management method for irrigated rice farming. vi University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS DECLARATION............................................................................................................................ i DEDICATION............................................................................................................................... ii ACKNOWLEDGEMENTS ........................................................................................................ iii ABSTRACT ................................................................................................................................... v TABLE OF CONTENTS ........................................................................................................... vii LIST OF TABLES ..................................................................................................................... xvi LIST OF FIGURES ................................................................................................................. xviii CHAPTER ONE ........................................................................................................................... 1 INTRODUCTION......................................................................................................................... 1 CHAPTER TWO .......................................................................................................................... 5 REVIEW OF LITERATURE ...................................................................................................... 5 2.1 Origin and distribution of rice............................................................................................... 5 2.2 Importance of rice ................................................................................................................. 5 2.3 Irrigated rice farming system ................................................................................................ 7 2.4 Importance of nitrogen in rice plant nutrition ....................................................................... 8 2.4.1 Effect of nitrogen fertilizer on plant growth .................................................................. 9 2.4.1.1 Plant height ............................................................................................................. 9 2.4.1.2 Number of tillers ................................................................................................... 10 vii University of Ghana http://ugspace.ug.edu.gh 2.4.1.3 Leaf area index (LAI) ........................................................................................... 11 2.4.1.4 Biomass accumulation .......................................................................................... 12 2.4.1.5 Leaf chlorophyll content ....................................................................................... 12 2.4.2 Effect of N fertilizer yield parameters of rice .............................................................. 13 2.4.2.1 Number of panicles ............................................................................................... 13 2.4.2.2 Panicle length ........................................................................................................ 14 2.4.2.3 Number of grains/ panicle ..................................................................................... 14 2.4.2.4 1000-grain weight ................................................................................................. 15 2.4.2.5 Grain yield ............................................................................................................ 15 2.4.2.6 Straw yield ............................................................................................................ 17 2.4.3 Effect of Nitrogen fertilizer on uptake and nitrogen use efficiency (NUE) of rice ..... 17 2.5 Water management practices in irrigated rice systems ....................................................... 18 2.5.1 Rice response to submerged water management ......................................................... 19 2.5.1.1 Plant growth ..................................................................................................... 19 2.5.1.2 Yield and yield parameters ................................................................................... 21 2.5.2 Rice response to Alternately Wet and Dry (AWD) water management ...................... 22 2.5.2.1 Plant growth .......................................................................................................... 22 2.5.2.2 Yield and yield parameters ................................................................................... 22 2.5.3 Rice response to moist water management .................................................................. 24 2.5.3.1 Plant growth ..................................................................................................... 24 viii University of Ghana http://ugspace.ug.edu.gh 2.5.3.2 Yield and yield parameters ................................................................................... 25 2.6 Water and nitrogen interaction............................................................................................ 26 2.7 Water productivity .............................................................................................................. 27 2.8 Water use economy ............................................................................................................. 28 CHAPTER THREE .................................................................................................................... 30 MATERIALS AND METHODS ............................................................................................... 30 3.1 Study Area .......................................................................................................................... 30 3.2 Soils of the study area ......................................................................................................... 31 3.3 Soil sampling and preparation for analysis ......................................................................... 31 3.4 Soil Analysis ....................................................................................................................... 31 3.4.1. Soil pH ........................................................................................................................ 31 3.4.2 Determination Nitrogen (N) ......................................................................................... 31 3.4.3 Determination of Phosphorus (P)................................................................................. 32 3.4.4 Determination of available Potassium (K) ................................................................... 32 3.4.5 Organic carbon determination ...................................................................................... 33 3.5 Pot Experiment.................................................................................................................... 34 3.5.1 Soil sampling and pot filling ........................................................................................ 34 3.5.2 Transplanting of seedlings ........................................................................................... 34 3.5.3 Design and layout of experiment ................................................................................. 34 3.6 Field Experiment ................................................................................................................. 35 ix University of Ghana http://ugspace.ug.edu.gh 3.6.1 Land preparation .......................................................................................................... 35 3.6.2 Field Layout ................................................................................................................. 35 3.6.3 Transplanting and gap filling ....................................................................................... 36 3.7 Fertilizer application ........................................................................................................... 37 3.8 Water Management Treatments .......................................................................................... 37 3.8.1 Submerged water condition ......................................................................................... 37 3.8.2 Moist soil condition ..................................................................................................... 37 3.8.3 Alternate wet and dry condition (AWD) ..................................................................... 38 3.9 Insect-pest management ...................................................................................................... 38 3.10 Weed management ............................................................................................................ 38 3.11 Harvesting and threshing .................................................................................................. 38 3.12 Data collection .................................................................................................................. 38 3.12.1 Growth parameters of rice ......................................................................................... 38 3.12.1.1 Plant height (cm) ................................................................................................. 39 3.12.1.2 Number of tillers ................................................................................................. 39 3.12.1.3 Dry matter accumulation..................................................................................... 39 3.12.1.4 Leaf Area Index .................................................................................................. 39 3.12.1.5 Determination of leaf chlorophyll content .......................................................... 39 3.12.1.6 days to 50 % flowering ....................................................................................... 39 3.13 Yield and yield parameters of Rice ................................................................................... 40 x University of Ghana http://ugspace.ug.edu.gh 3.13.1 Number of panicles m-2 .............................................................................................. 40 3.13.2 Length of panicle (cm) ............................................................................................... 40 3.13.3 Number of grains per panicle .................................................................................. 40 3.13.4 Percentage filled grains .............................................................................................. 40 3.13.5 1000- grain weight (g) ............................................................................................... 40 3.13.6 Grain yield ................................................................................................................. 41 3.13.7 Straw yield ................................................................................................................. 41 3.13.8 Harvest index .......................................................................................................... 41 3.14 Nitrogen uptake and Nitrogen Use Efficiency (NUE) ...................................................... 41 3.14.1 N uptake ..................................................................................................................... 41 3.14.2 Physiological N use efficiency (PNUE) .................................................................... 42 3.14.3 Agronomic N use efficiency (ANUE) ....................................................................... 42 3.15 Water Use Measurement ................................................................................................... 42 3.16 Water productivity ............................................................................................................ 42 3.17 Statistical Analysis ............................................................................................................ 43 3.18 Economic analysis for rice production ............................................................................. 43 3.18.1 Cost of cultivation ...................................................................................................... 43 3.18.2 Gross return ................................................................................................................ 43 3.18.3 Net return ................................................................................................................... 43 3.18.4 Benefit Cost ratio .................................................................................................... 43 xi University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR ....................................................................................................................... 44 RESULTS .................................................................................................................................... 44 4.1 Pot Experiment.................................................................................................................... 44 4.1.1 Vegetative Growth ....................................................................................................... 44 4.1.1.1 Plant height ........................................................................................................... 44 4.1.1.2 Number of tillers ................................................................................................... 45 4.1.1.3 Aboveground biomass accumulation .................................................................... 46 4.1.1.4 Leaf area index ...................................................................................................... 47 4.1.1.5 Leaf chlorophyll content ....................................................................................... 48 4.1.1.6 Days to 50% flowering ......................................................................................... 48 4.1.2 Yield and yield parameters .......................................................................................... 49 4.1.2.1 Effective tillers ...................................................................................................... 49 4.1.2.2 Panicle length ........................................................................................................ 50 4.1.2.3 Number of grains per panicle ................................................................................ 50 4.1.2.4 Percentage filled grains ......................................................................................... 51 4.1.2.5 1000 grain weight ................................................................................................. 51 4.1.2.6 Grain yield ............................................................................................................ 52 4.1.2.7 Straw yield ............................................................................................................ 53 4.1.2.8 Harvest index ........................................................................................................ 54 4.1.3 Water use (WU) ........................................................................................................... 54 xii University of Ghana http://ugspace.ug.edu.gh 4.1.4 Water productivity (WP).............................................................................................. 54 4.1.5 Grain N uptake ............................................................................................................. 55 4.2 Field experiment ................................................................................................................. 58 4.2.1 Vegetative Growth ....................................................................................................... 58 4.2.1.1 Plant height ........................................................................................................... 58 4.2.1.2 Number of tillers ................................................................................................... 58 4.2.1.3 Biomass accumulation .......................................................................................... 60 4.2.1.4 Leaf area index (LAI) ........................................................................................... 60 4.2.1.5 Leaf chlorophyll content ....................................................................................... 61 4.2.1.6 Days to 50% flowering ......................................................................................... 61 4.2.3 Yield and yield parameter ............................................................................................ 63 4.2.3.1 Number of panicles/m2 ......................................................................................... 63 4.2.3.2 Panicle length ........................................................................................................ 63 4.2.3.3 Number of grains per panicle ................................................................................ 63 4.2.3.4 Percentage filled grains ......................................................................................... 64 4.2.3.5 1000 grain weight ................................................................................................. 64 4.2.3.6 Grain yield ............................................................................................................ 65 4.2.3.7 Harvest index ........................................................................................................ 66 4.2.4 Water use ..................................................................................................................... 67 4.2.5 Water productivity ....................................................................................................... 67 xiii University of Ghana http://ugspace.ug.edu.gh 4.2.6 Grain N uptake ............................................................................................................. 67 4.2.7 Straw N uptake ............................................................................................................. 68 4.2.8 Agronomic nitrogen use efficiency (ANUE) ............................................................... 68 4.2.9 Physiological nitrogen use efficiency (PNUE) ............................................................ 68 4.2.10 Cost of cultivation ...................................................................................................... 69 4.2.11 Gross return ................................................................................................................ 70 4.2.12 Net profit .................................................................................................................... 70 4.2.13 Benefit cost ratio ........................................................................................................ 70 CHAPTER FIVE ........................................................................................................................ 72 DISCUSSION .............................................................................................................................. 72 5.1 Plant growth ........................................................................................................................ 72 5.1.1 Effect of N fertilizer on plant growth .......................................................................... 72 5.1.2 Effect of water management on plant growth .............................................................. 73 5.1.3 Interaction effect of water and N fertilizer on plant growth ........................................ 74 5.2 Effect of N fertilizer on yield and yield parameters ........................................................... 75 5.3 Effect of water management on yield and yield parameters of rice ................................... 75 5.4 Interaction effect of water and N fertilizer on yield and yield parameters ......................... 77 5.5 Effect of N fertilizer on N uptake and nitrogen use efficiency ........................................... 77 5.6 Effect of water management on N uptake, ANUE and PNUE of rice ................................ 77 5.7 Interaction effect of water and N fertilizer on N uptake and NUE ..................................... 78 xiv University of Ghana http://ugspace.ug.edu.gh 5.8 Effect of N fertilizer on water use and water productivity of rice ...................................... 79 5.9 Effect of water management on water use and water productivity ..................................... 79 5.10 Interaction effect of water management and N fertilizer on water use and water productivity ............................................................................................................................... 80 5.11 Cost-effectiveness of water use under various water management methods .................... 80 CHAPTER SIX ........................................................................................................................... 82 CONCLUSIONS AND RECOMMENDATIONS .................................................................... 82 6.1 Conclusions ......................................................................................................................... 82 6.2 Recommendation ............................................................................................................ 83 REFERENCES ............................................................................................................................ 84 APPENDICES………………………………………………………………………………...98 xv University of Ghana http://ugspace.ug.edu.gh LIST OF TABLES Table 1: Monthly climatic data of the study area during the experimental period ....................... 30 Table 2: Chemical characteristics of soil at 0-20 cm depth .......................................................... 33 Table 3:Description of treatments used in the pot experiment ..................................................... 35 Table 4:Description of treatments used in the field experiment ................................................... 36 Table 5:Effect of water management and N rate on plant height (cm) and number of tillers ...... 46 Table 6:Variation in above biomass accumulation, leaf area index, leaf chlorophyll content (SPAD values) and days to 50% flowering as affected by water management and N fertilizer rate ........ 49 Table 7: Effective tillers, panicle length, grains/panicle, % filled grains and 1000 grain weight as influenced by water and N fertilizer ............................................................................................. 52 Table 8: Straw yield, harvest index, water use and water productivity of rice as affected by water management and N fertilizer ......................................................................................................... 55 Table 9: Grain N uptake, straw N uptake ANUE and PNUE as influenced by water management and N fertilizer. ............................................................................................................................. 57 Table 10: Dynamics of plant height (cm) and tillering of rice as influenced by water management and N fertilizer rate. ...................................................................................................................... 59 Table 11: Above biomass accumulation of rice, Leaf area index, Leaf chlorophyll content (SPAD values) and days to 50 % flowering as affected by water management and N fertilizer. ............. 62 Table 12: Panicles/m2, panicle length, grains/panicle, % filled grains and 1000 grain weight as influenced by water and N fertilizer. ............................................................................................ 65 Table 13: Harvest index water use, water productivity, Grain N uptake, straw N uptake, ANUE, and PNUE as affected by water management and N fertilizer ..................................................... 69 xvi University of Ghana http://ugspace.ug.edu.gh Table 14: Cost of production, gross returns, net profit and benefit cost ratio as influenced by water management and N fertilizer ......................................................................................................... 71 xvii University of Ghana http://ugspace.ug.edu.gh LIST OF FIGURES Figure 1: Grain yield of rice as influenced by water management and N fertilizer (Pot Experiment). ....................................................................................................................................................... 53 Figure 2: Grain yield of rice as influenced by water management and N fertilizer (Field Experiment)................................................................................................................................... 66 xviii University of Ghana http://ugspace.ug.edu.gh CHAPTER ONE INTRODUCTION Rice (Oryza sativa L.) is a staple food for more than half of the world’s population (Kumar et al., 2015). The number of consumers is expected to increase in future due to increasing population, rapid urbanization and change in diets (Wassmann et al., 2009). About 79 million ha of irrigated lowlands account for 75% of the global rice production (Maclean et al., 2002). In Sub-Saharan Africa (SSA), although domestic production is disproportionate to consumption demand, the role of rice production still remains cardinal in improving food security for the growing population and contributing to poverty alleviation (Otsuka and Kijima, 2010). Traore (2005) estimated that, Africa produces about 14.6 million tons of rice per year on 7.3 million hectares. Out of the vast land available, West Africa has the largest planted rice area of about 1.1 million hectares (Traore, 2005), yet production levels are not able to meet local demands. As a result, SSA is said to account for a third of global rice imports to fill the gap in local demand at an alarming cost of more than US$4.3 billion per year, an amount which otherwise could be used in other areas of development (Nakano et al., 2011). According to Angelucci et al. (2013), most of the rice produced in Ghana is by smallholder farmers with farms of less than one hectare in size. Rice is considered to be the second most important staple grain food next to maize (MOFA, 2009) and the 5th most important source of energy in the diet accounting for 9 percent of total caloric intake (FAOSTAT, 2012). Rice now competes with vegetables and plantation crops such as citrus, oil paslm, cocoa and mango in lowland agriculture (Buri et al., 2012). Local rice production in Ghana satisfies only about 30 percent and the nation currently spends about US$450m annually to import rice to make up for the shortfall in supply 1 University of Ghana http://ugspace.ug.edu.gh (MOFA, 2010). Traditionally, lowland rice is grown under rain-fed with little or no water management from crop establishment to close to harvest. Many farmers rely mainly on rainfall and without any proper water management which makes the efficiency of fertilizer very minimal. In addition to high cost of fertilizers, poor water and nitrogen management have resulted in serious drawbacks in rice production by small-holder farmers who form the majority of the farming population. Nitrogen is the most essential nutrient element for rice growth and development. Though N supply drives rice production, low nitrogen use efficiency (NUE) is a key challenge in irrigated rice farming (Cassman et al., 1998). Nitrogen fertilizer under submerged water condition is subject to considerable changes due to chemical, physical, and biological processes, which lead to high losses via volatilization, denitrification, surface runoff and leaching. Nitrogen dynamics in submerged water management are different from that of that of alternate wet and dry water management regime (AWD) or moist soil condition. Studies conducted by Cabuslay and Alejar (2002) showed that, alternative wetting and drying increase nitrogen application efficiency compared to continually submerged water. On the contrary, nitrogen use efficiency was found to be less in AWD water management compared to submergence condition (Pirmoradian and Sepaskhah, 2006). Though Nitrogen plays vital role in rice cultivation, more dosage than necessary level causes’ harm to the environment and even decreases yield (Manzoor et al., 2006). Knowledge of N transformations in various water management regimes is essential not only to reduce the N fertilizer losses but also to minimize the environmental impacts. Rice is generally grown under continuous submergence to counter nutrient, water and weed stresses by pumping water from the rivers and their tributaries by either small diesel pumps or 2 University of Ghana http://ugspace.ug.edu.gh large electric pumping systems (Sing et al., 2002). Water and energy has therefore emerged to be key elements of sustainability of rice production. According to Sing et al. (1990) irrigation consumes about 82 % of the total operational energy input in rice cultivation. Moreover, worldwide fresh water resources are threatened by rapid global population growth and climate change. For instance, Orange and Limpopo River basins in Southern Africa and the Volta River basin in West Africa, are pressured with population densities and large-scale irrigation systems which put great strains on water resources availability in these areas (Ravenga et al., 2000). Furthermore, due to growing demand for water resources from all sectors, it is projected that by 2025, some countries in SSA including Ghana will face water stress (UNEP, 2008). Increasing competition from domestic and industrial users has further compounded the problem of water scarcity. Khan et al. (2006) envisaged that lesser amount of water will be available for agriculture and especially for rice, the crop that consumes the largest amount of freshwater. Water management is therefore critical for sustainable rice production in irrigated rice farming system. In order to improve water use efficiency and water productivity in irrigated rice, many water management techniques have been proposed, such as internal drainage (Ramasamy et al., 1997), AWD (Belder et al., 2004), soil water potential (Yang et al., 2005), continuous soil saturation (Borrell et al., 1997), and non-flooded mulching cultivation (Zhang et al., 2009). Considering the spiralling increase in cost of chemical fertilizer and huge competition for water for industrial, domestic and agricultural use, it is essential to identify efficient water management methods and optimum N fertilizer level for sustainable increase in rice productivity in irrigated rice farming system. In view of this, the research work was carried out to evaluate the effect of different water management methods and nitrogen fertilizer application rates on the growth and yield of irrigated rice in Ghana. 3 University of Ghana http://ugspace.ug.edu.gh The specific objectives of the study were; i. To determine the effect of different water management methods and different rates of nitrogen (N) fertilizer on growth and yield of rice in irrigated rice system. ii. To assess the effect of water management and N fertilizer on nitrogen uptake by rice in irrigated rice system iii. To evaluate water productivity and cost-effectiveness of water use under various water management methods. 4 University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO REVIEW OF LITERATURE 2.1 Origin and distribution of rice Rice (Oryza sativa L) is a grass (Gramineae) and belongs to the genus Oryza. Between 8000 and 15000 years ago, rice as a crop was first cultivated in south - East Asia, India and China (Normile, 2004). Nguyen et al. (2009) estimated that about 85% of the total rice production is mainly for human consumption. Rice is cultivated across all continents except Antarctica (Li and Li,2010). Archeological data revealed that Oryza.-sativa was domesticated some 7,000 years ago in Asia (Carney, 2000), although its antiquity and place of the origin is not well documented. Portères (1956), who discovered two loci of O. sativa introduction along the West African coast observed that rice varieties from Asia were easily adopted and integrated into rice farming systems in Africa since farmers in these areas were already familiar with rice cultivation. 2.2 Importance of rice Today, rice feeds more than half of the people on earth. It is the second most important cereal in the world today and provides together with wheat a large proportion (95%) of the total nourishment of the world’s population (FAO, 2004). David (1991) stated that Asia accounts for about 90 % of rice production in the world. Furthermore, Li (2003) estimated that the 155 million hectares planted throughout the world produce about 596.5 million metric tons of paddy rice per year. Per capita consumption and consumer demands for a given rice type also differ from region to region (Webb, 1991). Undoubtedly rice is now a major staple food for millions of people in West Africa (Basorun, 2003). Annual demand for rice in the Sub-Region is estimated at over 8 million metric tonnes and with rapid population growth (estimated at 2.6% per annum), increasing urbanization and the relative ease of preservation and cooking have influenced the growing trend in rice 5 University of Ghana http://ugspace.ug.edu.gh consumption (Khumbanyiwa 2003). Unfortunately, West Africa does not produce the quantity of rice needed to meet its demand and to fill that gap, rice has to be imported. Sub-Saharan Africa is said to account for a third of global rice imports to fill the gap in local demand at an alarming cost of more than US$4.3 billion per year, an amount which otherwise could be used in other areas of development (Nakano et al., 2011). Imports of this magnitude is worrying and represent a major setback for broader development and poverty reduction efforts in this sub region (Khumbanyiwa 2003). In Ghana, rice is considered to be the second most important staple grain food next to maize. According to Buri, et al. (2012), rice is now competing with other crops such as citrus, oil palm, cocoa, mango and vegetables in lowland crop cultivation. Local rice production in Ghana satisfies only about 30 percent and the nation currently spends about US$450m annually to import rice to make up for the shortfall in supply (MOFA, 2010). The increase in demand for imported rice is primarily attributed to increased income, good storability and ease of cooking (Shabbir et al., 2008). Rice consumption increased by over 20% per year in the 1990s, with the increased demand being met by imports from the Far East and the Americas (Berisavljevic et al., 2003). It has been reported that imported rice, which is also perceived to be of better quality than local rice, is generally sold at higher prices (Berisavljevic et al., 2003). Total rice consumption in Ghana in 2005 amounted to about 500,000 metric tonnes which is equivalent to per capital consumption of 22 kg per person (Tomlins et al., 2005). Furthermore, irrigated rice yields in Ghana are known to vary from 3.5 t/ha to 7 t/ha with an average yield of 4.6 t/ha on formal irrigation schemes (FAO, 2005). Despite the increases in rice production, Ghana still depends largely on imported rice to make up the deficit in rice supply. The self-sufficiency ratio of rice in Ghana has declined from 38 % in 1999 to 24 % in 2006 (Andriesse and Fresco, 2009). 6 University of Ghana http://ugspace.ug.edu.gh 2.3 Irrigated rice farming system Irrigated rice is mostly cultivated in bunded and puddled rice fields with one or more crops planted each year. According to George et al. (1992) lowland rice or irrigated rice usually refers to rice grown on both flat and slopping bunded fields with surface flooded during most of growing season. Usually, irrigation is the main water source in the dry season and is also used to supplement rainfall in the wet season. Mostly, water diversion from rivers and pump irrigation from wells are major sources of irrigation water. According to Humphreys et al. (2005) rice in the irrigated system is usually cultivated with water supplied by ground irrigation to supplement rainfall such that the standing depth of water maintained about 15 cm from crop establishment to close to harvest. Of all the different rice ecosystems, such as rainfed lowland and upland rice, irrigated rice farming system is the most dependable in Africa in terms of productivity. However, large areas in West Africa lacks fully developed irrigation system. A gradual increase in the 231, 000 ha observed in the irrigated ecosystem in 1980-84 had been expected (WARDA, 1993). Some African countries especially Egypt, Niger, Mauritania and Madagascar have large amounts of irrigated land planted to rice (WARDA, 2004). Main drawbacks linked to the irrigated systems include; nutrient deficiencies, poor water and nitrogen management, acidity, weeds, diseases including, Rice Yellow Mottle Virus (RYMV), blast, sheath rot, and bacterial leaf blight and insect pests (Traore, 2005). Rice yield of about 5000 to 7000 kg/ha can be realized if farmers employ optimum input management such as fertilizer, pesticide, seed, and appropriate water management in irrigated rice farming system (WARDA 1993). Lowland rice is mostly transplanted in puddled soil and farmers try to keep a fixed depth of ponded water on soil surface throughout the cropping season. Most often this modifies the soil structure considerably which may have adverse effect for all the succeeding cereal crops such as wheat, soybean and peanut (Hobbs & Gupta, 2003; Timsina and 7 University of Ghana http://ugspace.ug.edu.gh Connor, 2001). In lowland rice-based cropping systems fine texture soils are mostly used which are characterized by low percolation rates that allow an extended period of submergence. Under continuous submergences, soils become anaerobic which reduces nitrification and therefore allowing accumulation of NH –4 N which is essential for growing lowland rice (De Datta, 1995). 2.4 Importance of nitrogen in rice plant nutrition Nitrogen is the most essential element in determining the yield potential of rice (Cassman et al., 1996). Rice plants require N as much as possible at early and mid tillering to maximize panicle production. Nitrogen is also required at the reproductive and ripening stages in order to enhance number of grains/panicles plant and grain filling (Datta et al., 1986). Amount of N removal is estimated between 16 to 17 kg for the production of one ton of rough rice, and straw (Dobermann and Fairhurst, 2000). The efficiency of nitrogen uptake differs from 20 to 60 % based on the environmental conditions (soil type, water control, pH and water temperature), doses and modes of supply (split or not) as well as varieties (Karres et al., 1999). Conversion of nitrogen in nitrogenous fertilizer to ammonium is vital in the nutrition of irrigated rice (Gu et al., 2009), although rice can also remove the nitrate-N (Martens, 2001). According to Singh et al. (2002) ammonium-N fertilizer sources are highly recommended because the NH +4 is stable under flooded soil conditions. Excessive N availability in the soil does not only cause higher transpiration rates but also reduces available soil water especially during flowering and grain filling stage that may reduce grain yield (Song et al, 2010). In most cases, it is recommended to apply 120 – 180 kg of N per hectare at pre-flood to achieve a target nitrogen uptake of 130-150 kg N/ha at panicle initiation to obtain 12 t/ha rice yield (Nangia et al., 2008). 8 University of Ghana http://ugspace.ug.edu.gh 2.4.1 Effect of nitrogen fertilizer on plant growth 2.4.1.1 Plant height Application of optimum dose of nitrogen to rice is gaining importance because nitrogen plays a cardinal role in crop production. It is therefore crucial for individual farmer as well as to the country to get the optimum economic benefit out of a huge recurring expenditure in fertilizer. In an experiment to assess the effect of water stress and N fertilizer on growth and yield of rice, El- wahab et al. (2007) observed that, plant heights were significantly affected by N fertilizer application. The tallest plants were recorded when plants were treated with high N fertilizer rate. Plant height increased with increased N fertilizer application rate with plots without N fertilizer producing shorter plants. In a field experiment to evaluate the growth and yield responses of lowland rice with 4 nitrogen levels (0, 40, 80 and 120 kg ha-1) and placement methods, Lawal and Lawal (2002) concluded that plant height increased significantly up to 80 kg nitrogen ha-1. Similarly Hussain and Sharma (1991) reported that application of nitrogen up to 40 kg ha-1 increased plant height. However, at 80 kg and 120 kg ha-1, plant heights were non-significant among the treatments. Taller plants were obtained when plants were treated with 120 kg N/ha and the shorter ones from the control plots (Raju and Reddy 1992). Dahatonde (1992) concluded that N fertilization significantly influenced plant height. Also, in a field trial to determine the effect of different nitrogenous (N) fertilizers on growth, yield and quality of hybrid rice Variety, Chaturvedi and Chaturvedi (2005) found that, application of N fertilizers increased plant height significantly. The increase in plant height in response to application of N fertilizers was attributed to availability of nitrogen which enhanced more leaf area resulting in higher photo assimilates and thereby resulting in more dry matter accumulation. According to Malik et al. (2014), application of nitrogen level (140 kg N ha-1) increases plant height and there was a decrease in plant height with 9 University of Ghana http://ugspace.ug.edu.gh N rate below this rate. They argued that, although plant height is not a yield component especially in grain crops, it indicates the influence of various nutrients on plant metabolism. One of the most important functions of N in rice is the promotion of rapid growth through increase in height. 2.4.1.2 Number of tillers Number of tillers per unit area is one of the most important components of yield. The more the number of fertile tillers, the more the yield. Chaturvedi and Chaturvedi (2005) observed that, number of tillers / hill at 20 days after transplanting (DAT) were not significant among N fertilizer treatments. However, at 40, 60 and 80 days after transplanting the numbers of tillers / hill increased significantly (especially between 40-60 days after transplanting). There after a gradual decline was observed up to 80 days after transplanting. Studies by Gonzalez-dugo et al. (2010) on effect of nitrogen fertilizers on growth, yield and quality of hybrid rice (oryza sativa) revealed that, tiller production / hill was significantly affected by levels of nitrogen at all stages. Also, tiller number increases with increased nitrogen application rate. More number of tillers /m2 might be due to the more availability of nitrogen that played a vital role in cell division. Mannan et al., (2012) observed that tiller numbers varied significantly at different growth stages due to variation of N levels and genetic potentiality of variety. In their study they observed that, number of tillers decreases with decreased N fertilizer rate with the lowest number recorded in plots where N application was absent. Furthermore, El-wahab et al., (2007) revealed that tiller numbers at booting was significantly influenced by N fertilizer rate. The highest number of tillers were recorded when plants were treated with higher doses of nitrogen compared to lower N rates. Panda (1996) conducted a field experiment to assess the effect of nitrogen application as basal (45, 60 and 80 kg N ha-1) and top dressing (10, 30 and 45 kg ha-1) on the yield and yield components of Japonica rice and obtained high effective tillers hill-1 percentage of ripened grains and high grain yields from 45 10 University of Ghana http://ugspace.ug.edu.gh kg ha-1 (basal) and 45 kg ha-1 (top dressing). Similarly, Idris and Matin (1990) in their field experiment revealed that application of 140 kg N ha-1 produced maximum number of tillers hill-1 which was statistically identical to 60, 80, 100 and 120 kg N ha-1. Minimum tillers hill-1 was recorded from the control plots (0 kg N ha-1). Maske et al. (1997) concluded that, plant height, leaf area hill-1, number of tillers hill-1, dry matter hill-1 and grain yield increased significantly with increased N levels. 2.4.1.3 Leaf area index (LAI) Application of nitrogen fertilizer is believed to significantly influenced leaf area index of rice. According to Chaturvedi and Chaturvedi, (2005), application of higher dose of nitrogen produced higher leaf area index at flowering stage of plant growth compared to plots where there was no N application. They further observed that LAI decreases with decreased nitrogen application rate. They attributed these phenomena to possible improvement of nutrients availability and enhanced growth of plant by nitrogen application. Haque and Haque (2016) indicated that, leaf area index (LAI) was affected noticeably by adding nitrogen fertilizers at various growth stages of rice. Leaf area index progressively increased and achieved its maximum value (4.17) at 45 days after transplanting when fertilized with 100 kg N ha−1 whilst the lowest value (1.90) was recorded at control treatment (Haque and Haque 2016). A research conducted by Azarpour et al., (2014) revealed that, LAI values at lower nitrogen levels were lesser than higher levels. It was also observed that, maximum LAI was obtained at flowering stage (65 days after sowing) and then it reduced significantly. Leaf area increased as N application increased from 30, 60 and 90 kg/ha nitrogen which were significantly higher compared to the control treatment (Abou-khalifa, 2012). These were attributed to the positive effect of nitrogen on both leaf development and leaf area duration. According to Russo (1996), nitrogen enhances vegetative plant growth and to a certain 11 University of Ghana http://ugspace.ug.edu.gh extent large LAI leads to absorption of more solar radiation by plants. This promotes photosynthesis and ultimately leads to higher yield. LAI is related to the biologic and economic yields and increase in LAI causes higher yield (Singh et al., 2009). 2.4.1.4 Biomass accumulation According to Chaturvedi and Chaturvedi (2005), dry matter accumulation increased significantly with N fertilizer application in rice at all the growth stages of the crop. Biomass accumulation significantly increase due to nitrogen fertilizer throughout the measurement period. Significantly higher dry-matter accumulation (15.51 tonnes/ha) was obtained from 140 Kg N ha-1 at 95 days after transplanting (Rezaei et al., 2009). Ye et al. (2013) observed that dry matter accumulation increased at slow rate up to 30 days after transplanting and thereafter increased at faster rate up to harvest. Significantly higher dry-matter accumulation (11.41 tonnes/ha) was obtained from urea treatment at 95 days after transplanting which was superior to the control plots. The highest dry matter of nitrogen treated plants was attributed to the positive effect of nitrogen in some important physiological processes. Studies conducted by Rezaei et al. (2009) on the effects of irrigation and nitrogen management on yield and water productivity of rice revealed that N fertilizer application rate significantly influenced biomass accumulation. Application of higher dose of N produced higher biomass than lower application rate of N. Also, higher dry matter accumulation was attributed to increase in length and number of leaves, increase in number of tillers, elongation of stem and panicles and causing overall increase in vegetative growth of plant. 2.4.1.5 Leaf chlorophyll content Chlorophyll is a key pigment involved in photosynthesis which is the global biological process which supply energy for plants and other living things (Shpilyov et al., 2013). Kingori (2016) attributed higher leaf chlorophyll content in plants to increase availability of nitrogen to plants as 12 University of Ghana http://ugspace.ug.edu.gh nitrogen is essential for chlorophyll formation by plants. There was an increase in chlorophyll content of rice when nitrogen was applied. This resulted in increased photosynthesis process which led to more sugar formation (Dikshit and Paliwal, 1989). Work done by Verma et al. (2004) revealed that chlorophyll content in the third leaf of rice increased with increased nitrogen levels. Total chlorophyll content was gradually increased with increased N levels with 0 kg/ha to 200 kg/ha (Verma et al., 2004). 2.4.2 Effect of N fertilizer yield parameters of rice 2.4.2.1 Number of panicles In a study to investigate growth and yield of basmati and traditional aromatic rice as influenced by water stress and nitrogen level, Mannan et al. (2012) reported that yield parameter varied significantly due to variation of fertilizer N levels. Maximum number of panicles which were longer in length were found in the plots where higher doses of N was applied. On the contrary, lower number of panicles which were shorter in length were observed in plots where N was absent (Russo, 1996). Furthermore, Haque and Haque (2016) observed the highest number of panicle per hill (8.8) when 60 kg N ha−1 was applied and the lowest (7.07) from control treatment. Malik et al. (2014) revealed that, application of 120 kg N ha -1 gave the highest number of grains per panicles and longer panicles among the nitrogen levels. However lower values were recorded with decreased N levels. Studies conducted by Singh and Singh (1993) revealed that application of nitrogen fertilizer increases the number of grains per panicle as well number of productive tillers. Similarly, Jamil and Hussain, (2000) observed that application of 92 kg ha-1 N gave 114.75 numbers of grains per panicle which was significantly higher than the control. This probably was due to reduced competition for resources with these treatments compared to plots where there is no N fertilizer application. According to Ritesh et al. (2014) more number of productive panicles 13 University of Ghana http://ugspace.ug.edu.gh per m2 (364.71) as well as longer panicles (27.68 cm) were produced when plants were treated with 160 kg N ha-1 which remained statistically at par with that obtained by nitrogen application levels between 40 to 120 kg N ha-1. 2.4.2.2 Panicle length Field experiment conducted by Singh and Singh (1993) revealed that, panicle m-2, panicle length and grains/panicle increased due to application of 60 kg N ha-1. Similarly, Azad et al. (1995) stated that panicle length increased significantly when nitrogen rate was increased from 0 to 75 kg/ha. Mannan et al. (2012) observed longer panicles when rice plants were treated with higher doses of nitrogen. Idris and Matin (1990) concluded that the rate of nitrogen application influenced panicle length positively. 2.4.2.3 Number of grains/ panicle Hussain and Sharma (1991) stated that application of nitrogen fertilizer up to 80 kg N ha-l increased number of grains panicle-1. Nitrogen application at the rate of 120 kg ha-1 did not significantly affect the grains panicle-1. The highest number of grains panicle-1 produced at 80 kg N ha-1 and the lowest was produced at the 0 kg N/ha. In a field experiment to determine growth and yield of basmati and traditional aromatic rice as influenced by water stress and nitrogen level, Mannan et al. (2012) observed that grains panicle-1 increased with increased nitrogen application rate regardless of the water management treatments. They observed that more number of grains panicle- 1 were produced when plants were treated with 120 kg N ha-1 which was significantly superior to the control treatments. In a similar study, Abou-khalifa (2012) revealed that application of N fertilizers significantly increased the yield attributes of rice with 220 kg N ha-1 producing the highest value of grains per panicle (94.6), while unfertilized plants gave the lowest value of grains panicles-1. Chander and Pandey (1996) stated that a significant increase in grains panicle-l, tillers 14 University of Ghana http://ugspace.ug.edu.gh m-2 and grain yield were obtained from application of 120 kg N/ha compared to 60 kg N/ha. Tayefe et al.(2011) concluded that, increasing rates of applied N increased plant height, panicle m-2, grains panicle-1 and grain yield significantly. 2.4.2.4 1000-grain weight Field experiment conducted by El-wahab et al. (2007) showed that, nitrogen levels did not significantly influence 1000 grain weight of rice. They further suggested that, the genetic traits of the variety supersede that of the environmental conditions of which the plants were exposed to. Similarly, Jamil and Hussain (2000) concluded that, nitrogen rate had no significant influence on 1000-grain weight of rice. On the contrary, Islam et al. (1990) observed an increasing trend of 1000-grain weight with an increase in levels of nitrogen up to 80 kg ha-1. The lowest 1000 seed weight was recorded from application of 69 kg ha-1 N (22.7 g) while the highest of 26.3 was recorded when nitrogen rate was115 kg ha-1 N 2.4.2.5 Grain yield Field experiment conducted by Azarpour et al. (2014) revealed that, maximum grain yield (4328 kg/ha) was obtained from 90 kg/ha nitrogen fertilizer level with the minimum of 2734 kg/ha being obtained from the non-fertilizer treated plants. These showed that non application of nitrogen fertilizer decreases yield components and physiological indices. Singh et al. (2000) stated that incremental dose of N (100 kg N ha-1) gave significantly higher yields (2647 kg ha-1). According to Jamil and Hussain (2000) rice paddy yields were 1.91, 2.66 and 3.03 t ha-1 when nitrogen was applied 0 kg, 50 kg and 100 kg N ha-1 respectively. Chaturvedi and Chatusrvedi (2005) concluded that increasing nitrogen rate significantly enhanced paddy yield. Rice yield increased when N was applied of nitrogen up to 100 kg ha-1 and then decreased with increasing rate of nitrogen (Maskina et al. 1996). Application of nitrogen from 120 to 160 kg N ha-1 significantly reduced the yield, 15 University of Ghana http://ugspace.ug.edu.gh which was assumed to be due to excessive vegetative growth followed by lodging after flowering (Abou-khalifa, 2012). Similarly, application of nitrogen fertilizers had a significant effect on yield components with 80 and 120 kg N ha-1 markedly improved the grain yield by 17 and 45%, respectively (Raju and Reddy, 1992). Similarly, Singh and Pillai (1994) observed that, increased doses of nitrogen increased grain yield significantly up to 90 kg ha-1, after which it declined. According to Hossain et al. (1995), application of nitrogen up to 120 kg ha-1 significantly increased grain yield of rice. They observed with 40, 80 and 120 kg N ha-1 there was increase in yield over the control with 24, 33 and 34%, respectively. Similar, Thakur (1993) found that grain yield increased from 80 up to 120 kg N/ha. They recorded significantly higher yields with 80 and 120 kg N ha-1 than 0 and 40 kg N/ha. Hari et al. (1999) pointed out that grain yield increased as nitrogen application increase from 0 to 150 kg/ha, although a further increase up to 200 kg ha-1 did not increase grain yield. Kumar et al. (1996) observed higher grain yield at 160 kg N ha-1 over the control by 42.0 per cent. In a field experiment to investigate the best Irrigation method and nitrogen application on yield and productivity of rice at The Rice Research Institute of Iran during cropping season of 2006 and 2007, Rezaei et al. (2009) concluded that, best nitrogen practice was application of 60 kg/ha. They pointed out that using nitrogen more than 60kg/ha did not increase rice yield. Also, all the growth and yield forming characters increased linearly up to 60 kg N ha-1 and thereafter grain yield increased marginally. According to Mannan et al. (2012) grain yield of rice varied significantly due to the variation of nitrogen levels. Highest grain yield (4.22 t ha-1) was produced at higher doses of N application. 16 University of Ghana http://ugspace.ug.edu.gh 2.4.2.6 Straw yield According to Patel and Mishra (1994) application of 30, 60, 90 kg N ha-1 increased straw yields. Khanda and Dixit (1996) observed that straw yields were significantly influenced by increased levels of nitrogen. The maximum straw yields of 4.58 and 6.21 ha-1, respectively were obtained at 90 kg N ha-1 and 120 kg N ha-1. Murty et al. (1992) observed grain yields of 3.5, 4.2, 5.1, 5.5 t/ha and the straw yields were 4.2, 4.8, 6.0, 6.4 t ha-1, respectively by applying 0, 40, 80 and 120 kg N ha-1. Furthermore, Mannan et al. (2012) observed that straw yield was significantly influenced by N fertilizer and increasing levels of nitrogen increased the yield of grain and straw of rice. 2.4.3 Effect of Nitrogen fertilizer on uptake and nitrogen use efficiency (NUE) of rice As one of the most important staple foods for human nutrition, recent studies on rice have mostly focused on improving NUE especially in irrigated rice system. According to Husan et al. (2014) agronomic nitrogen use efficiency (ANUE) is a term used to describe the relative balance between the quantities of fertilizer N applied and yield produced. Study conducted by Duhan and Singh (2002) revealed that uptake of nutrients increased significantly with increasing N levels. Moreover, the application of nitrogen along with various green manuring (GM) showed additive effects on yield and uptake of nutrients. Under all green manuring treatments, the yield and uptake were always higher with 120 kg ha-1 than with lower level of nitrogen (Ritesh et al., 2014). Husan et al. (2014) observed that Nitrogen content, uptake, apparent N recovery and NUE were influenced significantly by the application of prilled urea and urea super granule alone or in combination with organic manure. They suggested that, application of Urea Supergranule (USG) in combination with poultry manure could be considered more effective for increasing the yield and NUE of rice. Experiments conducted by Ponnamperuma (1984) revealed that, even in the case of high yields of rice, about 76 to 80% of the total nitrogen uptake is derived from the soil in a single cropping 17 University of Ghana http://ugspace.ug.edu.gh season of rice. Also, N use efficiency (dry weight/N uptake) in grain is influenced by the sources of N fertilizers (Fageria et al., 2011). Haque and Haque, (2016) observed highest grain yield (5.36 t ha−1) when rice variety was fertilized with 60 kg N ha−1. Similarly Application of 60 kg N ha−1 also showed the highest nitrogen use efficiency (344.50 kg grain/kg N applied) of the variety. Jamil and Hussain, (2000) revealed that, among nitrogen levels, (0, 50 and 100 kg N ha-1), application of 100 kg N ha-1 resulted in maximum paddy sand total biomass yield of 3.03 and 9.74 t ha-1, respectively. They pointed out that, N uptake in both grain and straw increased significantly with increase in nitrogen application levels. Jing et al.(2007) revealed that, grain yield was enhanced linearly with the increasing N content of the upper two leaves, but hindered by the high N content of lower leaves. They further observed linear relationship between N uptake and leaf N content on a dry matter basis in all the leaves as N application rate increases. 2.5 Water management practices in irrigated rice systems About 70% of global fresh water resources are used by irrigated agriculture (FAO, 2007). Rapid population growth and increase in demand for extra water as a result of industrialization is forcing the agricultural sector to seek ways of using irrigation water more efficiently to produce more food (Suriadi, 2010). Moreover Smith (2008) suggests that, defining prudent planning and management of limited water resources in the sector of agriculture should be a regional and global interest. Rice is one of the principal users of the world’s freshwater resources due to continuous submergence of rice fields from crop establishment close to harvest (Bouman and Toung 2001, Toung and Bouman, 2003). However, current rice production is threaten by water scarcity due to competition for water and climate change (Belder et al., 2004). Bouman et al. (2007) envisaged that about 15- 20 million hectares of irrigated rice will experience some degree of water scarcity by the year 2025. Similarly, Tuong (2003) predicted that less water will be available for rice cultivation in the 18 University of Ghana http://ugspace.ug.edu.gh near future, due to increase competition for water among agricultural, domestic, hydropower and industrial water users. Wassmann et al. (2009) concluded that several areas which largely depend on rainfall for rice farming are already prone to drought under current erratic weather conditions and due to climate change, these areas are more likely to experience severe and frequent drought events in the near future. Increasing water productivity is especially vital because many processes in rice production area are related to water (Bouman, 2007). Therefore, efforts to increase water productivity by reducing water use are of great importance in irrigated rice farming. Most irrigated rice especially in the tropics are raised in a seedbed and then transplanted into a main field (De Datta, 1981). Main field Preparation often consists of soaking, plowing and puddling (i.e. harrowing under shallow submerged conditions). In irrigated rice farming, puddling is mostly done to control weeds and also to increase water retention and reduce soil permeability for easy leveling of the top field and transplanting of seedlings (De Datta, 1981). Between 25-50% water could be saved by intermitted irrigation during the vegetative stage without any adverse effect on rice yield (Anchal and Shiva, 2014). Various water management options for irrigated rice farming practices and their influence on performance of rice reported by different authors are presented below. 2.5.1 Rice response to submerged water management 2.5.1.1 Plant growth The rice crop grows better under continuously submerged soil conditions than other crops probably due to the fact that its root can tolerate the anaerobic soil condition (Suraidi, 2010). This practice in most cases keeps the rice field continuously submerged with water from crop establishment to close to harvest (Suriadi, 2010). Saied and Zoghdan (2012) observed that, plant height and number of tillers were significantly higher in continuous submerged treated plots than AWD water management. Similar trend was observed by Shirazi et al. (2014),where maximum plant height 19 University of Ghana http://ugspace.ug.edu.gh was recorded in 300mm irrigation treatment and shortest in the control. They pointed out that availability of well distributed soil moisture at different growth stages due to irrigation enhanced the growth of plant. Also research conducted by Khairi, et al. (2015) to effect of various water regimes on rice production in lowland irrigation revealed that, there were not significance differences in plant heights and tiller numbers when plants were grown under submergence and AWD water managements. Similarly, plant heights and tiller numbers were not statistically different under continuous submerged and AWD water management (Rezaei et al., 2009). A screen house experiment conducted by Nguyen et al. (2009) revealed that, mean plant height and tiller numbers of 6 rice cultivars were not significantly different when plants were treated with continuous submerged water management and intermittent water management system. They further point out that, dry matter accumulation for the initial harvest in the continuous submerged treatments was less than in the intermittent water treatment although these differences were not statistically significant. Glass house experiment conducted by Juraimi et al. (2009) revealed that, plant height at 15 and 30 DAS, did not show any significant difference. Differences in plant height were only recorded at the beginning of 45 DAS. The height of the rice plant increassd with time in all the flooding treatments until the time of harvest. Generally, rice plant which was exposed under continuous saturated and continuous field capacity conditions were significantly shorter than the rice plant which received continuous submergence (Saied and Zoghdan, 2012). However, effect of the submerged treatments on the height of the rice plant was not obviously significant in all the pots during the vegetative phase (15 and 30 DAS). This was attributed to the few and small rice tillers at the early growing stages, which minimized the competition for available water for growth, even under continuous saturated and continuous field capacity. Similar trend was observed in the case of effect of the continuous submerged treatments on rice tillering, during the early 20 University of Ghana http://ugspace.ug.edu.gh tillering stages, significant differences were not observed because the tillering process was just about to begin at this stage (Sariam, 2004). Mostly, number of tillers reached its maximum potential until 75 DAS and at 90 DAS, and tillering process start to slow down in most of the submerged treatments because the rice plants were found to reach their maturity and only a few small tillers were produced (Weerakoon et al., 2010). Weerakoon et al. (2010) further observed that, there was a significant increase of the total biomass in treatments where there is no moisture stress to the rice plant. Therefore maintaining rice plants under continuous submergence throughout the growing period resulted in a significant increase of the total biomass. Similarly, Zubaer et al. (2007) revealed that, dry matter accumulation as well as LAI were higher in continuous submergence plots than water stress plots at booting and harvest stages of plant growth. 2.5.1.2 Yield and yield parameters Effective panicles, the number of spikelets per panicle, the percentage of filled grains, and grain weight are the main yield factors. Khairi et al. (2015) observed higher number of effective tillers m-2 with continuous flooding followed by AWD water management. However, both were significantly superior to that obtained with continuous saturation. According to Zhang et al. (2009) the responses of rice panicle number m-2 were significantly affected by the submergence treatments. The highest number of rice panicles was produced under continuous submergence condition (434 panicles m-2), while the lowest was recorded when water kept at field capacity. A pot experiment conducted by Juraimi et al. (2009) to evaluate the effect of different flooding treatments on rice growth and yield revealed that, variability in the continuous submergence treatment did not significantly affect either the number of days to flowering or the number of days to grain maturity in all the pots. This according to Mardina (2005) and IRRI (2008) was due to the fact that at the flowering stage, water demand is very critical while low or deficit in water 21 University of Ghana http://ugspace.ug.edu.gh availability will delay and lengthen the time of flowering process. Research conducted by Belder et al. (2004) revealed that biomass, yield and yield components were statistically the same under AWD and continuous submerged water management regimes at regardless of levels for both the hybrid and inbred rice varieties. Similarly Khairi et al. (2015) observed higher yields in continuous flooding water treatments than AWD although the differences were not statistically different. Pot experiment conducted by Juraimi et al. (2009) revealed that, differences in the flooding treatments had significant effects on the yield of rice straw. They observed a general decreased in straw biomass and yield when water availability declined. 2.5.2 Rice response to Alternately Wet and Dry (AWD) water management 2.5.2.1 Plant growth In AWD irrigation technique, water is applied to the field a number of days after disappearance of ponded water. This differs from the traditional water management practice of continuous submergence of fields (Rejusus, 2011). This means that the rice fields are not kept continuously submerged but are allowed to dry intermittently during the rice growing stage (Rejesus, 2011). Field and pot experiments conducted by Vries et al.(2010) revealed that, AWD improved soil conditions and this encourages the development of tiller. It was also found that, there was no significance differences in biomass accumulation between AWD treatments and continuous submergence water condition. Nguyen et al. (2009) observed that, plant heights and tiller numbers in alternate wet and dry water treatments were not significantly different from continuous submergence treatments. 2.5.2.2 Yield and yield parameters According to Tan et al. (2013), alternate wetting and drying of fields enhance air exchange between the soil and the atmosphere and hence these condition promotes root growth and nitrogen 22 University of Ghana http://ugspace.ug.edu.gh uptake by rice. The performance of AWD in terms of rice yield are similar with submerged water management because AWD do not restrict water availability to plants (Belder, 2004). AWD technique depends much on other environmental factors such as soil type, water table depth and the number of days of absence of floodwater (Suriadi, 2010). During alternate wet and dry, water table coincides with root zone and therefore during the drying period plants may not experience water stress. They therefore produced similar yields as with continuously submerged conditions. Belder et al. (2004) reported that, aboveground biomass accumulation and rice yields were significantly similar under AWD and continuously submerged water management. AWD results in a better water productivity than submergence due to higher amount of water required. It was observed that with AWD at the vegetative stage of rice about 25-50% water could be saved without any significant reduction in rice yield (Ramamoorpy et al., 1993, Tajima, 1995). Boonjung and Funkai (1996) argued that, at the vegetative stage of the rice plant, rice growth was not adversely influenced when exposed to limited water condition. Hence AWD is preferable since at the vegetative stage of growth, rice adopts osmotic adjustment which enhanced dehydration tolerance in the rice plant (Steponkus et al., 1980). However, any water stress at late stages of growth can reduce rice yields significantly especially during early reproductive phase of rice (Kobata and Takami, 1981). In irrigated rice farming, continuous submergence is not necessary to obtain high yields (Guerra et al. 1998). According to Rezaei et al. (2009), rice plants grown under AWD water management conditions can give a yield 5-10% higher than continuous submergence. 23 University of Ghana http://ugspace.ug.edu.gh 2.5.3 Rice response to moist water management 2.5.3.1 Plant growth In moist soil condition, soil moisture is kept as close to saturation as possible by shallow irrigation so that about 2-cm floodwater depth is obtained every day (Tuong et al., 2005). According to Tabbal et al. (2002) moist water management can save about 30- 60% water compared with the conventional practice of continuous submergence while reduction of yield was only 4-9%. Because the water inputs decreased more than the yields, water productivity (calculated as the ratio of yield over total water input) increased by 30−115%. However, implementation of moist water management practice requires assured water supply throughout the growth period at the field level but frequent shallow irrigation is labour intensive (Suaridi 2010). Moist soil condition can be tedious to accomplish in coarse-textured soil due to its higher percolation rates compared with fine-textured soil (Suaridi 2010). According to Kukal et al. (2010) water deficit imposed during vegetative growth did not reduce yields while water stress during reproductive growth resulted in 20±70% less grain yield than well-irrigated rice. On the other hand, moist water conditions at late vegetative stage resulted in reduction in number of panicles per plant, percentage of filled grains and 1000- grain weight (Boonjung and Fukai, 1996). Again, Nour et al. (1994) observed that water stress during tillering and panicle initiation for 36 days significantly reduce plant height, tillering, total dry matter, and grain yield. It has been well established that water deficit reduces plant growth, primarily due to a reduction of the stomatal conductance that inhibits the carbon assimilation (Gonzalez-dugo et al., 2010) 24 University of Ghana http://ugspace.ug.edu.gh 2.5.3.2 Yield and yield parameters Under moist soil condition, water stress may develop in the rice plant, which will adversely affect crop growth and ultimately crop yield (Suriadi, 2010). The effect of water stress on rice yield and yield parameters largely depends on crop species or the variety. It also depends on the magnitude and the time of imposing water deficit. The effect of the magnitude and timing of water supply on crop growth and yield are of major importance (FAO, 1986). According to Andreas and Karen (2002), the most common effect of water stress is a decreased rate of growth and development of foliage. This has a cumulative effect through the season as plant stress early in crop development results in a reduced leaf area. This means that light interception is reduced, carbon assimilation is reduced and therefore the rate of leaf growth is reduced. Water level kept between field capacity and permanent wilting point had significant effect on yield and yield parameters of rice (Moutonnet, 2002). 2.5.4 Effect of water management on uptake and nitrogen use efficiency According to Olk and Senesi (2000) when fields are continuously submerged it brings about changes in the quality of soil organic matter. However, this practice enhances capacity of adequate nutrient-supply and soil carbon (soil organic matter) and yield (Dawe et al., 2000). Work done by Belder et al. (2004) reported that N uptake and NUE were similar when plants were treated under submerged and AWD management in their experiments. Usually, nitrogen uptake in both grain and straw in continuous submergence of fields was not significantly different from intermittent irrigation water management (Rejesus et al., 2011). Availability of nutrients such as nitrogen in crop field is largely influenced by partial aerobic soil conditions created by AWD. Tabbal et al. (1992) reported that, the level of ammonium was lower but nitrate levels were higher under AWD 25 University of Ghana http://ugspace.ug.edu.gh than under continuous submerged conditions. They pointed out that, in continuous submergence of fields nitrate could be leached or undergo denitrification losses making N uptake lower in continuous submergence than under AWD water management. Contrary to this, Bouman et al. (2006) observed significant decrease in NUE from 66-68% under flooded treatment to 40.2 % under AWD and 34.6% under saturated culture. Nitrogen use efficiency increased from 23.03 kg of grain/kg of N for rain-fed treatment to 30 kg of grain/kg of nitrogen for 100 % soil moisture deficit (SMD) irrigation treatment. Also higher nitrogen use efficiency is promoted at higher levels of water attributed to the better N mineralization and least nitrogen loss through leaching and volatilization at optimum soil moisture condition. This ultimately leads to better nitrogen uptake by rice (Blumenthal et al.,2008). 2.6 Water and nitrogen interaction Water management and N fertilization strategies are two of the most important factors for increasing plant biomass, grain yield, water use efficiency and nitrogen use efficiency of rice (Ye et al., 2013). According to Rezaei et al. (2009) maximum yield and water productivity are determined by minimum and optimized amount of nitrogen application. Similarly, El-wahab et al. (2007) observed yield of 10.86 t/ha when plants were treated with 120 kg N ha-1 under continuous submerged water condition. Nitrogen and water management and their interaction can support tactical decision making process in other to improve rice production (Belder et al., 2005). Water management with N fertilizer interaction still remains cardinal in rice production with regards to optimum yields, less water use and in increasing water productivity. Interaction of irrigation regime and nitrogen level on grain yield has been found to produce higher yieldswith the highest grain yield (7542 kg/ha) obtained when plants were treated with 120 kg N/ha under continuous submergence water condition. On the other hand, a lower grain yield of 4804 kg/ha was recorded 26 University of Ghana http://ugspace.ug.edu.gh with no fertilizer application under AWD water management regime. On the contrary, Cabangon et al. (2011) observed no interaction effect of water and nitrogen on rice yield, total N uptake, and N-use efficiencies. They concluded that, the principal effects of nitrogen management on rice under AWD are similar to those under continuous submergence conditions. Water treatment and nitrogen rate interaction for total N uptake was significant with 150 kg N/ha nitrogen rates under continuous submergence giving the higher uptake of nitrogen (Dunn and Gaydon, 2011) 2.7 Water productivity As far as agriculture is concerned, water productivity relates to the yield (biomass or grain) derived from using a specific quantity of water. Water productivity (WP) is the ratio of grain yield and total amount of water input (irrigation + rainfall) from time of transplanting till harvest (Molden, 1997). The factors which affect WP include; crop type, water availability and soil, agronomic and economic factors (Ali and Talukder, 2008). In an experiment, rice yields reduced significantly under AWD compared with continuously submerged water management. However, water productivity with respect to total water input was higher in AWD than continuous submergence because the yield reduction was lower than the amount of water saved (Bouman and Tuong, 2001). Many researchers suggest that, the total water input could decrease by 15 – 30 % without any significant impact on the grain yield (Cabangon et al., 2011; Belder et al., 2004). In an experiment conducted by Juraimi et al. (2009) it was observed that about 24 – 35 % and 70 % irrigation water could be saved if the field is either maintained at saturated condition or saturate to dry situation respectively. Aguilar and Borjas (2005) indicated that irrigated rice can be easily cultivated using 8000 to 10000m3/ha of fresh water. According to Bouman et al. (2006), modern rice cultivars when grown under flooded conditions, have water productivity (with respect to transpiration for grain yield (WPY/Tr)) of about 2 kg/m3, while water productivity with respect to total water input 27 University of Ghana http://ugspace.ug.edu.gh (irrigation plus rainfall) was around 0.4 kg/m3. Conventional water management in lowland rice aims at keeping the fields continuously submerged. Water inputs can be reduced and water productivity increased by introducing periods of non-submerged conditions of several days throughout the growing season unless cracks are formed through the plough sole (Belder et al., 2004). Water productivity in Sub-Saharan Africa ranges from 0.10 to 0.25 kg/m3. In the developed world water productivity is average at 0.47kg/m3. Compared to the developing world of 0.39kg/m3 (Kadigi, 2003). Bouman and Tuong (2001) found typical water productivities of 0.3–1.1 kg/m3 in the Philippines under continuous submergence water regime whilst water productivities in water- saving treatments were as high as 1.9 kg grain m–3. Since water scarcity is now of global concern, the aim of agriculture is to produce more rice with less amount water. Water is a scarce commodity, since we pay for the cost of water use and in many cases pay for the enormous environmental costs (Ali and Talukder 2008). 2.8 Water use economy Workdone by Rejesus et al. (2011) revealed that, alternate wetting and drying (AWD) decreases the frequency of irrigation to about 38%, without significant decrease in rice yields and net profits. Irrigation companies supply water to rice growers at a cost of about US$10 per ML and this cost is constantly increasing as the irrigation companies need to be economically viable (Bouman et al., 2002). The cost of pumping water from a river and its tributaries to rice growers is about $5 while the cost to growers of groundwater supplied to the crop is approximately $12 (Bouman et al., 2002). Globally, water productivity of rice ranged from 0.39 kg/m3 to 0.52 kg/m3 while in other cereals it ranged from 0.67 kg/m3 to 1.01 kg/m3 (Ximing and Rodegrant, 2003). According to Abdul-Ganiyu et al. (2015) it is more water productive to produce rice under intermittent irrigation than continuous submergence of fields since the amount in kg of rice grain produced per 28 University of Ghana http://ugspace.ug.edu.gh unit volume of water (m3) used was higher in intermittent irrigation than continuous submergence water management. According to Bouman et al. (2007) total water inputs, including rainfall, ranged from 965 mm for continuous submergence in rice cropping season. Barker et al. (1990) reported that, traditional irrigated rice production system not only leads to wastage of water, as it consumes 3000–5000 litres of water to produce 1 kg of rice but also causes environmental degradation and reduces fertilizer use efficiency. Saied and Zoghdan (2012) observed that, water productivity under saturated condition was higher than continuous submergence and half the amount of water was saved with comparable yield production. According to Aguilar and Borjas (2005) discontinuous submergence of fields brought about a reduction in pumping time, resulting in a relevant energy saving, and an important reduction in the overall costs. However, efficient utilisation of the applied N via fertilisers remains very low, that is only 20-40%. Mostly, increase in water productivity may or may not result in higher economic benefits (Visperas et al., 2005) 29 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE MATERIALS AND METHODS 3.1 Study Area The study was conducted at the Soil and Irrigation Research centre (SIREC) of the University of Ghana which is about 8 km away from the Kpong. The area lies between latitudes (00 04' E, 60 09' N) in the Eastern region of Ghana. It is part of the Accra plains and has annual rainfall between 800 and 1100mm. The major rainy season begins from April to mid-July while the minor rainy season from early September to mid-November. It is characterized by an average annual temperature of 28 ˚C and relative humidity between 59%-93%. Monthly climatic data of the study area during the experimental period is presented in Table 1. Table 1: Monthly climatic data of the study area during the experimental period Maximum Month Rainfall (mm) Relative humidity temperature (0C) July 2015 97.0 37.4 31.0 Aug 22.3 34.9 31.0 Sept 21.9 59.0 32.2 Oct 106.4 62.0 32.6 Nov 96.0 60.2 33.8 Dec N/A 23.0 34.2 Jan 2016 33.2 34.7 34.7 N/A- indicates data not available; Source: Ghana Meteorological Agency, Soil and Irrigation Research Center (SIREC), Kpong 30 University of Ghana http://ugspace.ug.edu.gh 3.2 Soils of the study area The soils in the study area are mainly the vertisols of the Accra plains. These are characterized by montmorillonitic clay minerals with clay content of 35–40%. The soils characteristically swell and become sticky when wet. When dried, they become harden and crack extensively which makes it difficult to cultivate with simple farm implements. Also, due to their narrow moisture range, tilling operations can be tedious with simple implements, e.g. hoe or with tractor drawn implements. Same soils were used for the pot experiments. 3.3 Soil sampling and preparation for analysis Soil was sampled at depth of 0-20 cm across the experimental field for laboratory analysis. In the laboratory, the soil samples were air-dried, crushed using mortar and pestle and then sieved through a 2 mm sieve and analyzed at the University of Ghana soil science laboratory. 3.4 Soil Analysis 3.4.1. Soil pH Ten grams of soil was weighed into beaker and 10 mL of distilled water was added to give a 1:1 (soil to water) ratio. The mixture was then stirred many times for about 30mins and left to stand for 1hr to allow most of the clay particles in suspension to settle. Two different buffer solutions of pH 4.0 and 7.0 were used to standardize the grass electrode pH meter- CG818, Schott Great. The electrode was then rinsed with distilled water, immersed into the partly settled suspension and the pH reading on the meter was recorded. 3.4.2 Determination Nitrogen (N) Total N in soil samples was measured following digestion using the micro – Kjeldahl digestion method. The micro- Kjeidahl digestion method results in direct oxidation of organic matter through 31 University of Ghana http://ugspace.ug.edu.gh use of a digestion mixture that contains concentrated sulphuric acid, (H2SO4), 30% hydrogen peroxide (H2O2), lithium sulphate (Li2SO4) and selenium (Se) powder. Selenium powder is used as a catalyst and Li2SO4 raises the boiling point of the mixture. An air dried soil sample weighing 0.5 g was weighed into a digestion tube followed by addition of 4.4 ml of digestion mixture. The resultant mixture was placed on a digester at 360 ºC for 2 hours. The solution was allowed to cool and 25 ml of 40 distilled water added. A further 75 ml of distilled water was added and the solution was allowed to settle. Total N in the sample was then determined colorimetrically at an absorbance of 655 nm. The % N in the sample was calculated as follows: % N = {(absorbance of sample – absorbance of blank) x F x 0.01}/sample weight Where F = the mean of (concentration of standards (ppm)/absorbance of standards) 3.4.3 Determination of Phosphorus (P) Sample digestion for total P was the same as in determination of total N (see section 3.3.3). After digestion, 5 ml of sample were pipetted into a 50 ml volumetric flask followed by 20 ml of distilled water. To the mixture, 4 ml ascorbic acid (C6H8O6) was then added and the resultant solution mixed well. Distilled water was added to the mark and the solution left for 1 hour for full colour development. The samples and standards were read at 880 nm wavelength. The % P in the sample and standards was calculated as follows: P = C x 0.05 x W Where C = concentration of P in sample; W = weight of sample. 3.4.4 Determination of available Potassium (K) Ten grams (10g) of soil that has been sieved through 2mm sieve was weighed into 200mL extraction bottle, 100mL of 1N ammonium acetate (NH4OAC) solution buffered at pH 7.0 was added to the soil the extraction bottle. The bottle and its content were placed in a mechanical 32 University of Ghana http://ugspace.ug.edu.gh shaker and shaken for 1hr, and the centrifuge in a centrifuge at 3000 rpm for 20 min. The solution was then filtered through Whatman No 42 filter paper into a clean bottle. An aliquot was taken from the filtrate in the bottle and used for determination of K. The atomic Absorption Spectrometer was used for reading the content of K in the solution and quantity in the soil determined. 3.4.5 Organic carbon determination Soil organic carbon was measured using the wet oxidation colorimetric method (Anderson and Ingram, 1993). One gram of soil sieved through a 2 mm sieve was weighed into a conical flask followed by addition of 10 ml potassium dichromate (K2Cr2O7). The resultant mixture was gently swirled until the sample was completely wet. To the mixture, 20 ml of concentrated H2SO4 were added from an automatic dispenser and the resultant mixture gently swirled. The mixture was allowed to cool in a fume cupboard followed by addition of 50 ml 0.4% BaCl2. The mixture was swirled again and left to stand overnight, so as to get a clear supernatant solution. Total organic C in the sample and standards was then measured calorimetrically using a 42 BUCK Scientific 100 VIS spectrophotometer at 600nm wavelength. The % organic C in the sample was then calculated as follows: % organic C = (K x 0.1)/ (W x 0.74) Where K = sample concentration – mean blank concentration W = weight of soil. Table 2: Chemical characteristics of soil at 0-20 cm depth Depth Exchangeable (cm) N% Available P Available K Ca pH OC 0-20 0.067 2.09 4.72 22.83 7.55 1.55 33 University of Ghana http://ugspace.ug.edu.gh 3.5 Pot Experiment The pot experiment was conducted as a preliminary study to help fine-tune the cultural practices and general management of the experiments. 3.5.1 Soil sampling and pot filling Soils for the pot experiment was taken from the soil and irrigation Research field (from a depth of 0-30 cm). Stones, debris and other foreign materials were carefully removed from the soil samples. The soil were sun-dried, crushed using a wooden mortar and pestle and then sieved through a 2 mm mesh. 9.0 kg sample was weighed into pots of volume 1,000 cm3. The soils in the pots were then submerged with water before transplanting. 3.5.2 Transplanting of seedlings The rice (Oryza sativa L.) variety used was Ex Baika. Two seedlings per pot were transplanted. During transplanting, all pots were kept saturated with water to prevent transplanting shock. 3.5.3 Design and layout of experiment A 3 x 3 factorial experiment was carried out in Greenhouse using a RCBD. In all 45 pots comprising of 9 treatments and 5 replications were used. The treatments used in the pot experiment are described in Table 3. 34 University of Ghana http://ugspace.ug.edu.gh Table 3: Description of treatments used in the pot experiment No. Treatment Code 1. Alternative Wet And Dry + 0kg N ha-1 AWDN0 2. Alternative Wet And Dry+ 60kgN ha-1 AWDN1 3. Alternative Wet And Dry + 90Kg N ha-1 AWDN2 4. Moist soil Condition + 0kgN ha-1 MoistN0 5. Moist soil Condition + 60kgN ha-1 MoistN1 6. Moist Condition + 90kgN ha-1 MoistN2 7. Continuous Submergence + 0kgN ha-1 SubmergedN0 8. Continuous Submergence + 60kgN ha-1 SubmergedN1 9. Continuous Submergence + 90kgN ha-1 SubmergedN2 3.6 Field Experiment 3.6.1 Land preparation The field was cleared with a cutlass and all vegetation and debris were removed. It was then flooded with irrigation water for about three (3) days to soften the soil to facilitate tillage. The field was then puddled to a depth of 15-20 cm by a rotovator in order to reduce water percolation and soften the soil for transplanting. 3.6.2 Field Layout A split plot design with water management treatments as main plot and N fertilizer treatments in subplots was used. The three water management methods were: Alternate wet and dry (AWD), moist soil condition between field capacity and permanent wilting point (Moist), and continuous submergence (submerged). The nitrogen levels were: 0, 60 and 90kgN ha-1 as subplots within each main plot. The main plots were separated from each other by bunds at a distance of 2m whiles 35 University of Ghana http://ugspace.ug.edu.gh metallic barriers of size 6m2 were then buried 30 cm deep in each sub plot to reduce lateral movement of water and nutrients. The treatments used are described in Table 4. 3.6.3 Transplanting and gap filling Rice variety, Ex Baika was used as the test crop. Seedlings were raised in the seedbed on 19th June, 2015. Twenty five days old seedlings were transplanted onto the field at spacing of 20 cm within rows and 20 cm between rows at 2 seedlings per hill. During planting, all the plots were kept saturated with irrigated water to prevent transplanting shock. Table 4: Description of treatments used in the field experiment Water management N fertilizer level Continuous submergence No nitrogen fertilizer (N0) (submerged) 60 kg N ha-1 (N1) 90 kg N ha-1 (N2) Alternate wetting and drying No nitrogen fertilizer (N0) (AWD) 60 kg N ha-1 (N1) 90 kg N ha-1 (N2) Moist soil condition (soil moisture No nitrogen fertilizer (N0) content between field capacity and 60 kg N ha-1 (N1) permanent welting point) (Moist) 90 kg N ha-1 (N2) 36 University of Ghana http://ugspace.ug.edu.gh 3.7 Fertilizer application Same nitrogen treatments were used for both pot and field experiments. The nitrogen fertilizer source was Urea. Nitrogen fertilizer was applied two times that is 50% at transplanting and 50% at panicle initiation for both pot and field experiments. Nitrogen fertilizer levels were 0, 60 and 90 kg N/ ha henceforth referred to as N0, N1 and N2, respectively. Straight fertilizers of triple Superphosphate (P2O5) and muriate of potash (k2O) was applied at a rate of 45 kg ha -1 as basal for all treatments in both pots and field after two weeks after transplanting of seedlings. 3.8 Water Management Treatments Water management treatments were the same for both experiments. After transplanting, all the plots were irrigated to maintain uniform moisture content at saturation for the first week to ensure full establishment of the seedlings. Perforated PVC pipes of about 20 cm in diameter and 45 cm in length were inserted in all plots except the submerged treated plots. The pipes were 15 cm above and 30 cm below the soil surface to monitor soil water levels in each plot. 3.8.1 Submerged water condition In the submerged water treatment, the depth of water was kept at 3 cm just after transplanting and increased gradually to 5–10 cm at active tillering (AT) stage and maintained until 10 days to harvest. 3.8.2 Moist soil condition In the moist water management regime, soils were just kept moist. This was achieved by ensuring that, the moisture level in the inserted tube within the plot is at 25 cm and 16 cm below the soil surface in the field and pot experiments respectively. All plots were continuously submerged at panicle primordial initiation stage until 10 days before harvest. 37 University of Ghana http://ugspace.ug.edu.gh 3.8.3 Alternate wet and dry condition (AWD) In the AWD water management regime, soils were kept inundated at 3 cm depth of water after transplanting. Plants were only irrigated when the water level in the pipe dropped to 25 cm and 16 cm below the soil surface in the field and pot experiments respectively. All plots were completely submerged at panicle primordial initiation stage until 10 days before harvest. 3.9 Insect-pest management Insecticide (dursban) was sprayed at vegetative stage to control stem borer infestation. The experimental field was covered with nylon nets from flowering stage till harvesting to prevent birds attack. 3.10 Weed management Pre- emergence herbicide (stump) was applied just after transplanting and followed by post- emergence herbicide (propagold = proppanil + 2, 4-D) application, 21 days after. 3.11 Harvesting and threshing The crop plot area was harvested manually using sickle. Harvested plants were sun dried for 5 days. Threshing was done manually, and grains were obtained by winnowing and were weighed at 14% moisture content. 3.12 Data collection 3.12.1 Growth parameters of rice The following growth data were collected: Plant height, leaf area index (LAI), number of tiller per plant, above ground biomass accumulation, leaf chlorophyll content and days to 50 % flowering. 38 University of Ghana http://ugspace.ug.edu.gh 3.12.1.1 Plant height (cm) Five healthy plants were tagged in each plot on which measurements were made. For juvenile plants, plant height was measured from ground level to the tip of the topmost leaf. For mature plants, however, plant height was measured from ground level to the tip of topmost panicle with a meter rule. The average value was considered to be the plant height for each treatment. 3.12.1.2 Number of tillers The number of tillers hill-1 were counted from five tagged plants in each experimental unit. 3.12.1.3 Dry matter accumulation Aboveground biomass was determined through destructive sampling of 3 hills per plot. The plant samples were put in brown paper envelopes and then oven dried at 60 0C for 48 hours to determine their dry matter weight. 3.12.1.4 Leaf Area Index Leaf area index were estimated by measuring the length and average width of leaf and multiplying by a factor of 0.75 followed by Yoshida (1981). 3.12.1.5 Determination of leaf chlorophyll content Chlorophyll content of leaves were recorded using SPAD value meter (Minolta Japan). The SPAD value of leaves was determined at flowering stage of the rice plant. For each plot, 15 leaves were randomly selected for measurement per treatment. 3.12.1.6 days to 50 % flowering Days to 50% flowering was recorded when about 50% of the plants within a plot had flowered. 39 University of Ghana http://ugspace.ug.edu.gh 3.13 Yield and yield parameters of Rice 3.13.1 Number of panicles m-2 Number of panicles m-2 per plot were recorded within each plot just before harvesting the crop. The average values were used to obtain the panicles m-1 per treatment. 3.13.2 Length of panicle (cm) The length of panicles were taken from five hills of each plot by random selection just before harvesting. Panicle length was recorded from the basal node of the rachis to the apex of each panicle with a centimeter rule. The means were calculated for each experimental unit. 3.13.3 Number of grains per panicle Just before harvesting panicles were taken from five hills of each plot. The numbers of filled and unfilled grains were counted to determine the number of filled grains per panicle. 3.13.4 Percentage filled grains Total filled grains were obtained in the panicles from five hills and this was used to determine percentage filled grains as per the formula. % filled grains = (Number of filled grains×100)/ Total number of grains 3.13.5 1000- grain weight (g) One thousand clean dried grains were counted from the seed stock obtained from five sample plants of-each plot and weighed by using an electronic balance. 40 University of Ghana http://ugspace.ug.edu.gh 3.13.6 Grain yield A 5 square meter area within each plot was used to grain yield in kg/ha. Grains obtained from each unit plot were sun dried and weighed carefully at 14% grain moisture content. The grain yield was finally converted to t/ha. 3.13.7 Straw yield Straw obtained from each unit plot 5m2 were dried in sun and weighed to record the straw yield/plot and finally converted to t /ha. 3.13.8 Harvest index Harvest index (HI) was determined using the formula; Grain yield Harvest index = Grain yield + straw yield 3.14 Nitrogen uptake and Nitrogen Use Efficiency (NUE) Tissue N concentration in both grains and straws samples were determined by micro Kjeldahl digestion, distillation, and titration to calculate aboveground total N uptake. Agronomic and physiological nitrogen efficiencies were calculated. 3.14.1 N uptake Nitrogen uptake were calculated as follows; Nitrogen uptake by grain (kg ha-1) = % N in grain ×Grain yield (kg ha-1) Nitrogen uptake by straw (kg ha-1) = % N in straw ×Straw yield (kg ha-1) Total nitrogen uptake (kg ha-1) = Nitrogen uptake by grain (kg/ha) + Nitrogen uptake by straw (kg/ha). 41 University of Ghana http://ugspace.ug.edu.gh 3.14.2 Physiological N use efficiency (PNUE) Physiological N use efficiency (PNUE) was calculated as follows; YF − YC PNUE = NUF − NUC Where; YF = Yield of fertilized plot (kg/ha), YC = Yield of control plot (kg/ha), NUF =Total N uptake in fertilized plot, and NUC = Total N uptake in control plot. 3.14.3 Agronomic N use efficiency (ANUE) Agronomic N use efficiency (ANUE) was calculated as; YF − YC ANUE = FN Where; YF = Yield of fertilized plot (kg/ha), YC = Yield of control plot (kg/ha) and FN = Fertilizer N applied (kg/ha). 3.15 Water Use Measurement Water was applied through a horse pipe and the amount of water consumed per plot was measured using containers with known volume. The amount of water-use was obtained from daily measurements. Depth of irrigation water (mm) applied was computed by dividing the volume of water applied by the area of the subplot. Also, amount of precipitation during the period (rainfall events and amounts) were recorded. 3.16 Water productivity GY Water productivity was calculated using the following equations; WP = TWA Where; WP = water productivity (kgm-3), GY = grain yield (kg/ha) and TWA = total water applied (irrigation water and rain water used) expressed in m3ha-1. 42 University of Ghana http://ugspace.ug.edu.gh 3.17 Statistical Analysis Data collected were subjected to analysis of variance (ANOVA) to find out the significance difference due to treatments using GenStat (12th Edition). Mean separation was done using least significance difference at 5% level of significance. 3.18 Economic analysis for rice production Only the field experiment was considered for the economic analysis. 3.18.1 Cost of cultivation Cost of agro inputs such as fertilizer and pesticides, labour, and other materials used in the field experiment were recorded. Water costs associated with water management techniques was also estimated. 3.18.2 Gross return Grain yield was converted into gross return from grain yield (GH₵/ha) based on prices of the local market. 3.18.3 Net return Net returns from sales of rice was calculated as; Gross returns - Cost of production 3.18.4 Benefit Cost ratio Benefit cost ratio was estimated using the formula; Gross return Benefit cost ratio = Cost of cultivation 43 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR RESULTS 4.1 Pot Experiment 4.1.1 Vegetative Growth 4.1.1.1 Plant height The data presented in Table 5 revealed that, plant height generally increased up to harvest stage ranging from 46.6 to 100.9 cm depending on water management and N fertilizer level used. The increment in plant height was most intense between active and maximum tillering stage. Plant height was significantly influenced by water management treatments (p<0.05) only at booting and harvest stages, while N fertilizer influenced plant height significantly (p<0.05) from active tillering to harvest. The interaction effect between water management and N fertilizer was significant at booting and harvest only (p<0.05). At active and maximum tillering stage, plant height was not influenced (p>0.05) by water management treatments. At booting, AWD and submerged water treatments produced significantly taller plants than plants treated with moist water management. The same pattern was observed at harvest. At active and maximum tillering, N1 and N2 treated plants produced significantly (p<0.05) taller plants, while plants that were not treated with N fertilizer (N0) produced shorter plants. At harvest, plant height significantly increased with increased N rate. There was significant interaction effect between water management and N fertilizer at booting and harvest stages. At both stages, the interaction effect of N2 with submerged water management produced significantly taller plants followed by N2 treated plants under AWD water management. The interaction effect of N0 and moist water management resulted in significantly shorter plants. 44 University of Ghana http://ugspace.ug.edu.gh 4.1.1.2 Number of tillers The mean values of the number of tillers across the treatments (Table 5) showed that tillering increased up to maximum tillering stage and thereafter gradually declined. The number of tillers were significantly influenced by N fertilizer (p<0.05) at all stages. Also, number of tillers was significantly influenced by water management (p<0.05) at all stages except at active tillering. There was significant effect (p<0.05) of interaction between water management and N fertilizer on number of tillers except at active tillering stage. At maximum tillering, booting and harvest stages, tillering, was not significant (p>0.05) among AWD and submerged treated plants. However, moist water treatments produced significantly lower number of tillers. With regards to N fertilizer, tillering was similar in N1 and N2 treatments in all growth stages except at harvest. At harvest, tiller number was significantly higher in N2 treated plants than N1. N0 treated plants produced significantly lower number of tillers in all stages of growth. At booting and harvest, interaction effect of N2 with submerged water management produced higher tillers followed by N2 treated plants under AWD water management. In all, tillering was significantly lower in N0 and moist interaction of fertilizer and water management. 45 University of Ghana http://ugspace.ug.edu.gh Table 5: Effect of water management and N rate on plant height (cm) and number of tillers Plant height (cm) Tiller numbers Treatment Active Maximum Active Maximum tillering tillering Booting Harvest tillering tillering Booting Harvest Water (W) AWD 47.4 72.3 88.2 88.7 6 22 20 19 Moist 46.6 70.8 71.9 85.0 5 20 17 14 Submerged 47.8 71.6 88.8 89.4 6 22 20 19 LSD (P=0.05) NS NS 0.59 1.0 NS 0.5 0.8 0.9 Fertilizer (N) N0 45.3 69.7 76.3 76.8 5 17 15 14 N1 47.6 72.1 81.5 87.0 7 23 21 18 N2 48.9 73.0 91.2 99.3 7 24 22 20 LSD (P=0.05) 1.2 1.4 0.59 1.0 1.3 1.1 1.1 0.9 Interaction AWD×N0 45 70.0 80.7 77.8 5 18 17 15 AWD×N1 47.6 72.8 86.0 87.4 6 23 22 20 AWD×N2 49.6 74.1 98.0 101 7 24 22 21 Moist×N0 45.4 66.0 69.1 74.2 5 14 12 12 Moist×N1 47.0 71.3 72.1 85.8 6 22 19 14 Moist×N2 47.4 72.2 76.9 95.1 6 23 21 18 submerged×N0 45.4 70.1 81.4 78.5 6 19 17 15 submerged×N1 48.1 72.2 86.5 87.7 7 24 22 19 submerged×N2 49.7 72.6 98.6 102 7 25 23 22 LSD (P=0.05) NS NS 1.1 1.78 NS 0.9 1.4 1.6 Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05. 4.1.1.3 Aboveground biomass accumulation Biomass accumulation across the treatment increased from mid-tillering up to harvest (Table 6). Biomass accumulation ranged from 5.4 g to 79.2 g across the treatment combinations. Biomass accumulation was significantly influenced by water and as well as N fertilizer at mid-tillering, booting and harvest. Also the interaction effect between water management and N fertilizer was significant at booting and harvest only. At mid-tillering and booting, AWD and submerged treated plants produced similar biomass accumulation with the least biomass accumulation recorded in 46 University of Ghana http://ugspace.ug.edu.gh moist water treatments. At harvest however, biomass accumulation was significantly varied in this order: submerged > AWD > moist. At mid- tillering and booting, N1 and N2 treated plants produced higher biomass accumulation than plants that were not treated with N fertilizer (N0). At harvest, biomass accumulation significantly increased with increased N rate. Interaction effect of N2 with submerged water treatments produced higher biomass accumulation followed by N2 fertilized plants under AWD water management at booting and harvest stages. 4.1.1.4 Leaf area index Leaf area index across all treatments increased from booting to flowering and ranged from 3.6 to 7.6 (Table 6). Leaf area index was significantly influenced by both water management and N fertilizer as well as interaction effect of these two factors at both growth stages. At booting, leaf area index was similar in AWD and submerged treated plants. At flowering stage, submerged water treatments was superior to all the other water treatments. For both growth stages, the lowest leaf area index was recorded in moist water management. Based on N fertilizer rate, leaf area index varied significantly (p<0.05) and ranked as N2 > N1 > N0. At booting, the interaction effect of N2 with submerged water treatment produced higher leaf area index followed N2 and AWD combination. However at flowering, interaction effect of N2 with AWD produced higher leaf area index followed by N2 with submerged water treatments. Interaction effect of N0 and moist was inferior to all other treatment combinations. 47 University of Ghana http://ugspace.ug.edu.gh 4.1.1.5 Leaf chlorophyll content Leaf chlorophyll content ranged from 30.6 µmol/m2 to 55.6 µmol/m2 across the treatment combinations as presented in Table 6. Both water management and N fertilizer as well as interaction effect of water and N fertilizer significantly influenced leaf chlorophyll content. At flowering, leaf chlorophyll content was significantly higher in submerged treatments than the other water treatments. Moist treated plants produced the lower chlorophyll content at flowering stage. Leaf chlorophyll content significantly (p<0.05) increased with increased N rate. The interaction effect of N2 with submerged water treatments produced higher leaf chlorophyll content followed by N2 and AWD interaction at flowering stage. In all, interaction effect of N0 with moist produced the lowest chlorophyll compared to all the other treatment combinations. 4.1.1.6 Days to 50% flowering The data on days to 50 % flowering are also shown in Table 6. Water management and N fertilizer application as well as their interaction did not significantly (p>0.05) influenced days to 50% flowering. 48 University of Ghana http://ugspace.ug.edu.gh Table 6: Variation in above biomass accumulation, leaf area index, leaf chlorophyll content (SPAD values) and days to 50% flowering as affected by water management and N fertilizer rate Above biomass accumulation (g) Leaf area index Leaf Days to Treatment chlorophyll 50% Mid tillering Booting Harvest Booting Flowering content flowering Water (W) AWD 7.3 49.2 60.4 5.8 5.8 42.5 84 Moist 6.2 34.2 46.2 4.7 4.7 38.3 84 Submerged 7.6 49.8 64.5 5.9 6.0 43.9 85 LSD (P=0.05) 0.46 0.84 0.77 0.16 0.14 0.94 NS Fertilizer (N) N0 6.4 27.2 44.3 4.3 4.3 33.5 84 N1 7.3 52.7 57.0 5.2 5.2 39.9 84 N2 7.5 53.4 69.9 6.9 7.0 51.3 84 LSD (P=0.05) 0.45 0.84 0.77 0.15 0.14 0.94 NS Interaction AWD×N0 6.8 29.6 48.3 4.5 4.5 34.5 83 AWD×N1 7.6 58.7 56.9 5.6 5.6 39.7 84 AWD×N2 7.6 59.5 76.1 7.3 7.6 53.4 84 Moist×N0 5.4 21.9 35.7 3.6 3.6 30.6 84 Moist×N1 6.6 40 48.4 4.6 4.6 39.4 84 Moist×N2 6.7 40.7 54.4 5.9 5.9 44.9 85 submerged×N0 6.9 30 48.8 4.8 4.8 35.4 85 submerged×N1 7.7 59.5 65.6 5.6 5.6 40.7 85 submerged×N2 8.1 59.9 79.2 7.4 7.5 55.6 84 LSD (P=0.05) NS 1.5 1.33 0.27 0.25 1.64 NS Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05. 4.1.2 Yield and yield parameters 4.1.2.1 Effective tillers Average number of effective tillers per pot across all treatments ranged from 12 to 22 depending on water management and N fertilizer used (Table 7). In general, the number of effective tillers/pot was significantly influenced by both water management and N fertilizer (p<0.05). Also, the 49 University of Ghana http://ugspace.ug.edu.gh interaction effect of water management and N fertilizer was significant. Number of effective tillers did not differ significantly between AWD and submerged water treatments. However both water treatments were significantly superior to moist water treatment. Number of effective tillers increased with increased N rate with the lowest number of tillers being recorded in plants treated with no N fertilizer (N0). Interaction effect of N2 and submerged produced higher number of effective tillers followed by N2 and AWD interaction. In all, N0 with moist interaction was inferior to all other interaction effect. 4.1.2.2 Panicle length Panicle length differed significantly with water management and N fertilizer as well as interaction effect of water management and N fertilizer (p<0.05) as shown in Table 7. Panicle lengths were at par in AWD and submerged water treatments but significantly shorter in moist water treatments. The trend of panicle length with regard to N fertilizer was N2 > N1 > N0. Interaction effect of N0 with moist water produced the shortest panicle length in all the treatment combinations. Interaction effect of N2 with submerged was significantly (p<0.05) superior to all the other interaction effects. 4.1.2.3 Number of grains per panicle Data on the number of grains per panicle are presented in Table 7. Number of grains/panicle was significantly (p<0.05) influenced by water management and N fertilizer. Also, the interaction effect of water management and N fertilizer on number of grains per panicle was significant (p>0.01). AWD and submerged produced similar number of grains/panicle however, moist treated plants produced the lowest number of grains/panicle. With response to N fertilizer, number of grains/panicle increased with increased N application rate with the lowest number produced in N0. Interaction effect of N2 with submerged and N0 with moist produced the highest and lowest number of grains/panicle respectively. 50 University of Ghana http://ugspace.ug.edu.gh 4.1.2.4 Percentage filled grains Percentage filled grains ranged from 88.3 to 93.7 % (Table 7) depending upon treatment combination. Percentage filled grains was significantly (p<0.05) influenced by N fertilizer treatments but not by water management. N2 and N1 did not differ in percentage filled grains but lowest percentage filled grains was recorded in N0. The interaction of water management and N fertilizer on percentage filled grains was non-significant (p>0.05). 4.1.2.5 1000 grain weight Thousand grain weight was not significantly influenced by both N fertilizer and water management (Table 7). Also, there was no interaction effect of water management and N fertilizer on 1000 grain weight. However, moist and AWD water management regime produced higher 1000 grain weight (26.9 g) although not significantly (p>0.05) different from submerged water treatment. N1 and N2 treated plants produced 1000 grain weight of 27.0 g which was not significantly (p>0.05) different from plants with no N application (27.3 g). The highest weight (27.5 g) was recorded in N1 treated plants under submerged although not significantly different from the other treatment combinations. The lowest weight (26.5 g) was recorded in N2 treated plants under AWD water management. 51 University of Ghana http://ugspace.ug.edu.gh Table 7: Effective tillers, panicle length, grains/panicle, % filled grains and 1000 grain weight as influenced by water and N fertilizer Effective Panicle % filled 1000 grain Treatment tillers length(cm) Grains/panicle grains weight(g) Water (W) AWD 19 22.6 113 91.7 26.9 Moist 14 21.3 96 92.6 26.9 Submerged 19 22.7 115 89.1 27.4 LSD (P=0.05) 0.9 0.59 4.1 NS NS N Fertilizer (N) N0 14 20.8 98 89.8 27.3 N1 18 22.2 103 92.1 27.0 N2 20 23.8 124 91.4 27.0 LSD (P=0.05) 0.9 0.59 4.1 1.3 NS Interaction AWD×N0 15 20.8 100 89.3 27.4 AWD×N1 20 22.6 106 93.7 26.9 AWD×N2 21 24.5 134 92.0 26.5 Moist×N0 12 20.1 91 88.3 27.1 Moist×N1 14 21.4 95 89.0 26.6 Moist×N2 18 22.4 102 90.0 27.1 Submerged×N0 15 20.83 103 91.7 27.3 Submerged×N1 19 22.7 108 93.7 27.5 Submerged×N2 22 24.8 135 92.3 27.4 LSD (P=0.05) 1.6 1.1 7.1 NS NS Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05. 4.1.2.6 Grain yield The effect of different water management and N fertilizer rate on rice yield for the pot trial is shown in figure 1. Grain yield was significantly influenced by water management and N fertilizer. Also, the interaction effect of water management and N fertilizer on grain yield was significant. Grain yield ranged from 14.9 to 54.6 g/pot. The effect of N fertilizer on rice yield was ranked as: N2 > N1 >N0. AWD and submerged produced similar yields. Grain yield was lowest in moist treated plants. Interaction effect of N2 with submerged water management gave higher yields 52 University of Ghana http://ugspace.ug.edu.gh followed by N2 with AWD interaction. N0 with moist interaction was significantly (P<0.01) inferior to all other interaction effect of water management and N fertilizer. 70 60 50 40 N0 30 N1 N2 20 10 0 AWD Moist Submerged Water management Figure 1: Grain yield of rice as influenced by water management and N fertilizer (Pot Experiment). Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. 4.1.2.7 Straw yield Straw yield ranged from 35.7 to 79.2 g/pot across the treatment combinations as presented in Table 8. Both water management and N fertilizer significantly influenced straw yield. The water management effect on straw yield was ranked in the order: submerged > AWD > moist. For N fertilizer, the trend of straw yield was N2 > N1 > N0. Interaction effect of N2 with submerged and N0 with moist gave significantly (p<0.01) higher and lower straw yields respectively 53 Grain yield ( g/pot) University of Ghana http://ugspace.ug.edu.gh 4.1.2.8 Harvest index Both water management and N fertilizer application rate significantly (p<0.01) influenced harvest index of rice (Table 8). There was interaction effect of water management and N fertilizer on harvest index of rice. Harvest index ranged from 0.29 to 0.41 across the treatment combinations. Harvest index increased significantly (p<0.05) with increased N fertilizer rate. With respect to water managements, AWD produced the greatest harvest index which was significantly (p<0.01) different from submerged and moist water treatments. Moist water treatments produced the lowest harvest index than submerged treatments. Interaction effect of N1 treated pots with AWD proved significantly (p<0.05) superior to all other interaction effect of N fertilizer and water management. 4.1.3 Water use (WU) Water use was significantly (p<0.05) influenced by both water management and N fertilizer application rate (Table 8). Interaction effect of water management and N fertilizer significantly (p<0.05) influenced water use. Water use ranged from 23.1 cm3 to 57.8 cm3 depending upon water management and N fertilizer used. For N fertilizer, the trend of response of water use was N2 > N1 > N0. Water use with regards to water management was ranked in this order: Moist < AWD < submerged. With interaction effect of water management with N fertilizer, more water was required (57.8 cm3) with submerged and N2 interaction followed by N1 with submerged interaction. The lowest WU (23.1 cm3) was recorded at N0 treatment under moist water management. 4.1.4 Water productivity (WP) Both water management treatments and N fertilizer, and their interactions had a significant (p<0.05) effect on water productivity (Table 8). Water productivity ranged from 0.47 to 1.09 g cm-3 across the treatments combinations. In all cases, water productivity increased with increased 54 University of Ghana http://ugspace.ug.edu.gh N fertilizer application rate. In relation to water management treatments, water productivity was ranked in this order: moist > AWD > submerged. In general, the interaction effect of N2 with moist water management produced higher WP followed by N1 with same water management. The lowest WP (0.47 g cm-3) was observed at N0 with submerged interaction. Table 8: Straw yield, harvest index, water use and water productivity of rice as affected by water management and N fertilizer Water use Treatment Straw yield (g) Harvest index (cm3) WP (g/cm3) Water (W) AWD 60.4 0.39 49.3 0.79 Moist 46.2 0.36 27.2 0.96 Submerged 64.5 0.37 54 0.72 LSD (P=0.05) 0.77 0.04 0.95 0.3 N Fertilizer (N) N0 44.3 0.32 40.6 0.55 N1 57.0 0.39 43.0 0.91 N2 69.9 0.4 46.7 1.03 LSD (P=0.05) 0.76 0.04 0.96 0.3 Interaction AWD×N0 48.3 0.34 48 0.51 AWD×N1 56.9 0.41 49.3 0.82 AWD×N2 76.1 0.41 50.5 1.05 Moist×N0 35.7 0.29 23.1 0.65 Moist×N1 48.4 0.38 26.4 1.06 Moist×N2 54.4 0.39 32.0 1.09 Submerged×N0 48.8 0.33 50.8 0.47 Submerged×N1 65.6 0.38 53.3 0.76 Submerged×N2 79.2 0.41 57.8 0.95 LSD (P=0.05) 1.33 0.07 1.66 0.05 Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. 4.1.5 Grain N uptake Grain N uptake was significantly (p<0.05) influenced by both water and nitrogen fertilizer (Table 9). Also, interaction effect of water management and N fertilizer on grain N uptake was significant 55 University of Ghana http://ugspace.ug.edu.gh (p<0.05). With regards to N rate, uptake increased with increased N rate. Response of N uptake in grain with regard to water management was ranked in the order: AWD > submerged > moist. Interaction effect of N2 with AWD gave higher uptake followed by N2 with submerged interaction. 4.1.6 Straw N uptake The effects of water management and N fertilizer on straw nitrogen uptake are presented in Table 9. Both water and N fertilizer and their interaction significantly (P<0.05) influenced N uptake in straw. N uptake in straw ranged from 0.15 to 0.72 g pot-1. N uptake with regards to N fertilizer was ranked as: N2 > N1 > N0. Among the water treatments, N uptake was ranked in this order: submerged > AWD > moist. Interaction effect of N2 with submerged recorded higher uptake followed by N2 with AWD interaction effect of N fertilizer and water management. 4.1.7 Agronomic nitrogen use efficiency (ANUE) ANUE was significantly (p<0.05) influenced by both nitrogen fertilizer and water treatments as well as interaction effect of water management and N fertilizer (Table 9). Agronomic N use efficiency ranged from 25.9 to 34.9g/g across the treatments combinations. ANUE of rice was significantly higher in N2 than N1, whereas based on water treatments ANUE varied in the order: submerged > AWD > moist. For the interaction effect, ANUE was significantly (p<0.05) higher (34.9g/g) in N2 with submerged followed by N2 with AWD interaction. 4.1.8 Physiological nitrogen use efficiency (PNUE) Data presented in Table 9 showed that, both water management and N fertilizer as well as interaction effect of water management and N fertilizer had significant (p>0.05) effect on PNUE. PNUE ranged from 29.6 to 48.2g/g across the treatment combinations (Table 9). PNUE decreased 56 University of Ghana http://ugspace.ug.edu.gh with increased fertilizer rate with the highest recorded in N1. In case of water management, PNUE in AWD was at par with submerged. PNUE in moist was superior to AWD and submerged water treatments. Interaction effect of N1 with AWD as well as N1 with moist had the highest PNUE (48.2g/g) followed by N1 with submerged interaction. Table 9: Grain N uptake, straw N uptake ANUE and PNUE as influenced by water management and N fertilizer. Grain N uptake Straw uptake Treatment (g/pot) (g/pot) ANUE(g/g) PNUE(g/g) Water (W) AWD 0.37 0.43 19.5 25.9 Moist 0.2 0.34 16.3 32.1 Submerged 0.34 0.45 20.9 25.8 LSD (P=0.05) 0.04 0.05 0.93 5.4 N Fertilizer (N) N0 0.12 0.20 - - N1 0.29 0.34 26.7 50.4 N2 0.51 0.62 29.9 33.4 LSD (P=0.05) 0.04 0.05 0.93 3.6 Interaction AWD×N0 0.14 0.28 - - AWD×N1 0.34 0.36 26.3 48.2 AWD×N2 0.63 0.70 32.1 29.6 Moist×N0 0.08 0.15 - - Moist×N1 0.22 0.26 25.9 48.2 Moist×N2 0.31 0.45 22.8 37.6 Submerged×N0 0.13 0.23 - - Submerged×N1 0.33 0.41 27.7 44.3 Submerged×N2 0.57 0.72 34.9 33.0 LSD (P=0.05) 0.07 0.09 1.6 6.5 Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. 57 University of Ghana http://ugspace.ug.edu.gh 4.2 Field experiment 4.2.1 Vegetative Growth 4.2.1.1 Plant height In the field experiment, plant height was recorded from active tillering up to harvest stage and its value ranged from 43.4 to 101.4 cm (Table 10). The plant height increased faster from active to maximum tillering stage. Plant height was significantly (p<0.05) influenced by water management treatments at all growth stages except active tillering, while N fertilizer influenced plant height significantly (p<0.05) from active tillering to harvest. The interaction effect between water management and N fertilizer was significant at booting and harvest only. At active and maximum tillering stage, plant height was not influenced (p>0.05) by water management treatments. At maximum tillering and booting, plant height in AWD was at par with submerged water treatments, while plants treated with moist water management produced significantly shorter plants. Plant heights were similar in N1 and N2 while N0 produced shorter plants. At harvest the trend was in the order: N2 > N1 > N0. Interaction effect between water management and N fertilizer was significant only at booting and harvest stages. At both stages, the interaction effect of N2 with submerged water management produced significantly taller plants followed by N2 treated plants under AWD water management. On the other hand, the interaction effect of N0 and moist water management resulted in significantly shorter plants. 4.2.1.2 Number of tillers Tillering increased up to maximum tillering and thereafter gradually declined till harvest (Table 10). The number of tillers were significantly influenced by N fertilizer at all stages. Also, number of tillers was significantly influenced by water management at all stages except active tillering. AWD and submerged water treatments produced similar tillers at booting and harvest stages. Moist 58 University of Ghana http://ugspace.ug.edu.gh water treatments produced significantly lower number of tillers (p<0.05). With regards to N fertilizer, tillering was at par in N1 and N2 treatments in all growth stages except at harvest. At harvest stage, tiller number was significantly (p<0.05) ranked in the order: N2 > N1 > N0. In all, N0 treated plants produced significantly lower number of tillers. At booting and harvest, interaction effect of N2 with submerged water management produced higher tillers followed by N2 treated plants under AWD water management. In both cases, tillering in N0 with moist interaction was inferior to all other interaction effects. Table 10: Dynamics of plant height (cm) and tillering of rice as influenced by water management and N fertilizer rate. Plant height (cm) Tillers/m2 Treatment Active Maximum Active Maximum tillering tillering Booting Harvest tillering tillering Booting Harvest Water (W) AWD 46.3 70.8 95.7 97.3 139 475 408 369 Moist 44.8 68.8 77.5 79.6 131 414 319 281 Submerged 46.9 70.9 95.8 97.8 158 486 414 356 LSD (P=0.05) NS 1.13 0.57 0.6 NS 24.4 15.4 14.8 Fertilizer (N) N0 43.7 68.6 85.4 85.8 119 350 308 267 N1 46.4 70.6 91.8 93.3 147 503 336 317 N2 47.9 71.5 92.0 95.6 161 522 497 422 LSD (P=0.05) 1.9 2.0 0.46 0.75 17.5 20.4 9.2 10.5 Interaction AWD×N0 42.9 68.7 90.4 92.3 117 383 325 300 AWD×N1 46.7 70.9 98.3 98.7 142 508 358 358 AWD×N2 49.3 73.0 98.6 100.7 158 533 542 450 Moist×N0 43.4 67.4 75.2 72.2 100 275 267 225 Moist×N1 45.5 69.5 78.5 82.1 142 475 283 258 Moist×N2 45.4 69.5 78.9 84.6 150 492 408 358 submerged×N0 44.7 69.5 90.5 92.9 142 392 333 275 submerged×N1 47 71.4 98.4 99.2 158 525 367 333 submerged×N2 49.2 72.0 98.6 101.4 175 542 542 458 LSD (P=0.05) NS NS 0.76 1.14 NS 33.7 17.7 18.4 Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05 59 University of Ghana http://ugspace.ug.edu.gh 4.2.1.3 Biomass accumulation Data presented in Table 11 showed that, biomass accumulation across the treatment increased from active tillering up to harvest. Biomass accumulation ranged from 125g to 1405.2g across the treatment combinations. Biomass accumulation was significantly influenced by water and N fertilizer at maximum, booting and at harvest. Also the interaction effect between water management and N fertilizer was significant (p<0.05) only at booting and harvest. At maximum tillering and booting, AWD and submerged treated plants produced similar biomass with the least biomass recorded in moist water treatments. At harvest however, biomass accumulation significantly (p<0.05) varied in this order: Submerged > AWD > moist. At maximum tillering and booting stage, similar trend was observed in N1 and N2 treated plants while plants treated without N fertilizer (N0) produced lower biomass. At harvest, biomass accumulation significantly increased with increased N rate. At both booting and harvest stage, interaction effect of N2 with submerged water treatments produced higher biomass accumulation followed by N2 fertilized plants under AWD water management. 4.2.1.4 Leaf area index (LAI) Leaf area index increased from booting to flowering and ranged from 3.1 to 7.4 (Table 11). Leaf area index was significantly (p<0.05) influenced by both water management and N fertilizer as well as interaction effect of both factors. At both stages, leaf area index was similar in AWD and submerged treated plants but the lowest leaf area index was recorded in moist water treatments. Based on N fertilizer rate, leaf area index varied significantly (p<0.05) and ranked as N2 > N1 > N0 at both growth stages. The interaction effect of N2 with submerged was at par with interaction effect of N2 with AWD. In all cases, interaction effect of N0 and moist was significantly (p<0.01) inferior to all other treatment combinations. 60 University of Ghana http://ugspace.ug.edu.gh 4.2.1.5 Leaf chlorophyll content At flowering, Leaf chlorophyll content ranged from 30.1 to 55.6 µmol/m2 across the treatment combinations as presented in Table 11. Both water management and N fertilizer as well as interaction effect of water and N fertilizer significantly (p<0.05) influenced leaf chlorophyll content. Leaf chlorophyll content varied significantly with regards to water management treatments and ranked as follows: Submerged > AWD > moist. Leaf chlorophyll content significantly (p<0.05) increased with increased N rate with the lowest chlorophyll content recorded in N0 treated plant. The interaction effect of N2 with submerged water treatments produced higher (42.7 µmol/m2) leaf chlorophyll content followed by N2 and AWD interaction at flowering stage. In all, interaction effect of N0 with moist produced the lowest (30.1 µmol/m2) chlorophyll compared to all the other treatment combinations. 4.2.1.6 Days to 50% flowering Water management and N fertilizer application as well as their interaction did not significantly influence days to 50% flowering (Table 11). Generally it took between 83 and 85 days for the test variety Ex. Baika to reach 50 % flowering, when various water management and N fertilizer treatments were imposed. 61 University of Ghana http://ugspace.ug.edu.gh Table 11: Above biomass accumulation of rice, Leaf area index, Leaf chlorophyll content (SPAD values) and days to 50 % flowering as affected by water management and N fertilizer. Above biomass accumulation (g) Leaf area index Leaf Days to Treatment Active Maximum chlorophyll 50% tillering tillering Booting Harvest Booting Flowering content flowering Water (W) AWD 144.2 329.7 526.1 1329.5 5.3 5.8 37.4 84 Moist 137.7 232.2 430.5 1083.9 4.2 4.8 33.9 85 Submerged 140.3 349.7 533.8 1341.6 5.5 5.9 38.2 85 LSD (P=0.05) NS 71.3 9.5 16.82 0.3 0.27 0.3 NS Fertilizer (N) N0 133.9 271.1 346.1 1088.3 3.9 4.3 32.1 84 N1 136.9 315.0 570.7 1330.3 4.7 5.3 36.6 84 N2 151.1 325.6 573.2 1336.4 6.5 6.9 40.8 84 LSD (P=0.05) NS 39.2 5.33 10.11 0.13 0.21 0.48 NS Interaction AWD×N0 137.5 273.3 377.5 1186.7 4.2 4.4 32.6 83 AWD×N1 144.2 348.3 598.3 1400.0 4.9 5.6 37.7 84 AWD×N2 150.8 367.5 602.4 1401.9 6.9 7.4 42.0 84 Moist×N0 125.0 239.2 270 868.3 3.1 3.8 30.1 84 Moist×N1 138.3 224.2 509.8 1185.8 4.1 4.5 33.8 85 Moist×N2 149.2 233.3 511.6 1197.6 5.5 6.0 37.7 85 submerged×N0 139.2 300.8 391.7 1210.0 4.4 4.5 33.7 85 submerged×N1 128.3 372.5 604.1 1405.2 5.1 5.7 38.2 85 submerged×N2 153.3 375.8 605.7 1409.7 7.0 7.4 42.7 84 LSD (P=0.05) NS NS 10.62 16.82 0.31 0.35 0.66 NS Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05. 62 University of Ghana http://ugspace.ug.edu.gh 4.2.3 Yield and yield parameter 4.2.3.1 Number of panicles/m2 The effect of different water management and N fertilizer rates on number of panicles/ m2 are shown in Table 12. Mean number of panicles/m2 ranged from 232 to 403 depending on water management and N fertilizer used. Number of panicles/m2 was significantly (p<0.05) influenced by both water management and N fertilizer. Interaction effect of water management and N fertilizer was significant (p<0.05). Number of panicles/m2 in AWD were at par with submerged water treatments. However, moist treated plants produced significantly lower panicles/m2. With regards to N fertilizer rates, panicles/m2 varied significantly and was ranked in the order: N2 > N1 > N0. Interaction effect of N2 with submerged produced higher number of panicles/m2 followed by N2 and AWD interaction. In all, N0 with moist interaction was inferior to all other interaction effect. 4.2.3.2 Panicle length Variation of panicle length as influenced by water and N fertilizer ranged from 20.1 to 24.3 cm (Table 12). Interaction effect of water management and N fertilizer on panicle length was significant (p<0.05). Panicle lengths were similar in AWD and submerged water treatments but significantly (p<0.05) shorter in moist water treatments. The trend of panicle length with regard to N fertilizer was N2 > N1 > N0. Interaction effect of N0 with moist water produced the shortest panicle length in all the treatment combinations. Interaction effect of N2 with submerged produced longer panicles compared to all the other treatment combinations. 4.2.3.3 Number of grains per panicle Data on the number of grains/panicle are presented in Table 12. Number of grains/panicle was significantly influenced by water management and N fertilizer. Also, the interaction effect of water management and N rate on number of grains per panicle was significant (p<0.05). Number of 63 University of Ghana http://ugspace.ug.edu.gh grains/panicle was not significant among AWD and submerged treatment but, moist treated plants produced significantly (p<0.05) lower number of grains/ panicle. Based on N fertilizer, the number of grains/panicle varied in the order: N2 > N1 > N0. With interactions, N2 with submerged and N0 with moist interaction produced significantly (p<0.05) higher and lower number of grains/panicle respectively. 4.2.3.4 Percentage filled grains Percentage filled grains were significantly influenced N fertilizer treatments (p<0.05) and ranged from 86.0 to 94.0 % (Table 12). Interaction effect of water management and N fertilizer on percentage filled grains was also significant (p<0.05) but effect of water management on percentage filled grains was not significant (p>0.05). N2 and N1 did not differ in percentage filled grains but lower percentage filled grains was recorded in N0. Interaction effect of N2 with submerged gave the best grain filling followed by N0 with submerged interaction. Grain filling was poorer in N1 with moist interaction compared to all other treatment interaction. 4.2.3.5 1000 grain weight The effect of water management and N fertilizer on 1000 grain weight is presented in Table 12. N fertilizer and Water management as well as their interaction did not significantly (p>0.05) affect 1000 grain weight. However, 1000 grain weight ranged from 26.4 to 27.5 g. 64 University of Ghana http://ugspace.ug.edu.gh Table 12: Panicles/m2, panicle length, grains/panicle, % filled grains and 1000 grain weight as influenced by water and N fertilizer. Panicle % filled 1000 grain Treatment Panicle/m2 length (cm) Grains/panicle grains weight (g) Water (W) AWD 349 22.2 127 90.9 26.8 Moist 319 21.3 99 92.4 26.9 Submerged 350 22.6 128 89.1 27.4 LSD (P=0.05) 10.2 0.48 1.1 NS NS N Fertilizer (N) N0 261 22.8 106 90.2 27.1 N1 355 23 115 89.9 27.1 N2 401 23.1 133 92.3 27 LSD (P=0.05) 12.3 0.37 2.4 1.1 NS Interaction AWD×N0 275 20.1 113 89.0 26.9 AWD×N1 369 22.6 124 91.2 27.1 AWD×N2 401 24 147 92.0 26.4 Moist×N0 232 20.1 93 90.3 27.1 Moist×N1 324 21.3 98 86.0 26.6 Moist×N2 400 22.4 105 91.0 27.1 Submerged×N0 277 20.8 113 91.3 27.2 Submerged×N1 271 22.7 124 92.0 27.5 Submerged×N2 403 24.3 148 94.0 27.4 LSD (P=0.05) 18.7 0.63 3.4 2.2 NS Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05. 4.2.3.6 Grain yield The effect of various water management and N fertilizer rate on rice yields is shown in Figure 2. In water management treatments, grain yield in AWD was at par with submerged water treatment, while moist water treatment produced significantly lower grain yield (p<0.05). Differences in yield among the N levels was in the order: N2 > N1 > N0. With regards to interaction effect, the highest grain yield (6.5 t/ha) was recorded in N2 with submerged interaction followed by N2 with AWD 65 University of Ghana http://ugspace.ug.edu.gh interaction which produced grain yield of 6.4 t/ha. The lowest grain yield (2.2 t/ha) was recorded in N0 treated plants in moist water condition. 8 7 6 5 4 N0 N1 3 N2 2 1 0 AWD Moist Submerged Water management Figure 2: Grain yield of rice as influenced by water management and N fertilizer (Field Experiment). Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. 4.2.3.7 Harvest index The influence of water management and N fertilizer application rates on harvest index (HI) of rice is presented in Table 13. HI was not significantly (p>0.05) influenced by water management and N fertilizer but interaction effect of water management and N fertilizer on harvest index of rice was significant. Harvest index ranged from 0.47 to 0.51 across the treatment combinations. The 66 Yield (t/ha) University of Ghana http://ugspace.ug.edu.gh greatest harvest index (0.51) was recorded in N0 with moist interaction followed by interaction effect of N1 with AWD and N2 under moist water condition which recorded harvest index of 0.50. 4.2.4 Water use Water use was significantly (p<0.05) influenced by both water management and N fertilizer application rate (Table 13). Also, interaction effect of water management and N fertilizer application on water use was significant. Water use based on total water input (irrigation+ rainfall) ranged from 524mm to 1608 mm depending upon water management and N rate used. In the case of water management, less water was required to produce rice under AWD than submerged. The least water requirement was observed in moist treatment. In case of N fertilizer, water use was in the order: N2 > N1 > N0. For interaction effect, water use was lower (524 mm) in N0 with moist interaction while N2 with submerged recorded the highest water (1608mm) 4.2.5 Water productivity Both water management treatments and N fertilizer application rates, and their interactions had a significant (p<0.05) effect on water productivity of rice (Table 13). It ranged from 0.20 to 0.73 kg m-3 across the treatments. With water treatments, WP was greatest in moist followed by AWD treatments. The least WP was recorded in submerged treatments. Among the N rates, WP varied significantly in this order: N2 > N1 > N0. The highest WP (0.73 kg m-3) and lowest WP (0.2 kg m-3) were observed by N2 and moist interaction and N0 and submerged interaction respectively. 4.2.6 Grain N uptake N uptake in grain was significantly influenced by both water and N fertilizer as shown in Table 13. Also, interaction effect of N fertilizer and water management on grain N uptake was significant. Grain N uptake ranged from 11.45 to 89.61 kg N ha-1 across the treatments combinations. Grain 67 University of Ghana http://ugspace.ug.edu.gh N uptake in AWD was similar to submerged treatments. The lowest was recorded in moist treatment. Grain N uptake significantly increased with increased N rate. With regards to interaction effect, grain N uptake was higher (89.61 kg N ha-1) in N2 with AWD interaction followed by N2 with submerged interaction. Interaction effect of N0 with moist produced the lowest grain N uptake. 4.2.7 Straw N uptake The effect of water management and N fertilizer on N uptake in straw is presented in Table 13. Water management, N fertilizer and interaction effect of water and N fertilizer significantly influenced N uptake in straw. N uptake in straw ranged from 6.72 to 61.70 kg N ha-1. N uptake in AWD was at par with submerged treatments but significantly (p<0.05) lower in moist. For N fertilizer rate, the trend was: N2 > N1 > N0. With interaction effect, N2 with submerged and N0 with moist interaction produced the highest and lowest straw N uptake respectively. 4.2.8 Agronomic nitrogen use efficiency (ANUE) ANUE was significantly influenced by nitrogen fertilizer and water treatments as well as their interaction effect (Table 13). Agronomic nitrogen use efficiency ranged from 20.6 to 38.5g/g across the treatments combinations. ANUE in AWD and submerged water treatments were not statistically different (p>0.05). ANUE was significantly lower in moist treatments (p<0.05). For N fertilizer, the trend of ANUE of rice was N2 > N1 > N0. 4.2.9 Physiological nitrogen use efficiency (PNUE) N fertilizer significantly influenced PNUE but water management and interaction effect of water management and N fertilizer was non-significant (Table 13). Mean PNUE ranged from 29.6 to 68 University of Ghana http://ugspace.ug.edu.gh 52.0g/g across the treatments combinations. Among the N fertilizer rate, PNUE increased with decreased N rate. Table 13: Harvest index water use, water productivity, Grain N uptake, straw N uptake, ANUE, and PNUE as affected by water management and N fertilizer Water Water Grain Straw Harvest use productivity uptake uptake Treatment index (mm) (kg/m3) (kg/ha) (kg/ha) ANUE(g/g) PNUE(g/g) Water (W) AWD 0.49 1075 0.43 48.6 33 22.7 27 Moist 0.49 572 0.58 26.7 20.7 15.1 28 Submerged 0.48 1558 0.2 46 33.9 21.7 25 LSD (P=0.05) NS 213 0.02 2.93 0.77 3.59 NS N Fertilizer (N) N0 0.49 1023 0.3 15.7 10.4 - - N1 0.48 1067 0.44 33.2 25.2 25.6 47.3 N2 0.49 1115 0.57 72.4 52.1 33.9 31.9 LSD (P=0.05) NS 235 0.02 2.35 0.73 2.92 3.36 Interaction AWD×N0 0.47 1031 0.28 18.2 13 - - AWD×N1 0.5 1062 0.44 38.1 27.1 29.4 52.0 AWD×N2 0.49 1132 0.57 89.6 59 38.5 29.5 Moist×N0 0.51 524 0.42 11.5 6.7 - - Moist×N1 0.47 588 0.58 25.1 19.8 20.6 46.0 Moist×N2 0.48 604 0.73 43.5 35.6 24.8 36.7 submerged×N0 0.49 1514 0.2 17.4 11.4 - - submerged×N1 0.47 1552 0.3 36.4 28.7 26.7 44 submerged×N2 0.48 1608 0.4 84.1 61.7 38.5 29.6 LSD (P=0.05) 0.02 363 0.04 3.94 1.16 4.88 NS Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. NS = not significant at P > 0.05 4.2.10 Cost of cultivation The data in Table 14 showed that the cost of cultivation of rice ranged from GH₵2945 to GH₵3953.3 across the treatments in the field experiment. In general N2 fertilizer application rate required the higher cost of production followed by N1 fertilizer rate while N0 required the lowest cost of production. In the case of water management, Submerge water condition required higher 69 University of Ghana http://ugspace.ug.edu.gh cost of production compared to AWD water treatment. Moist water treatment required least cost of production. Cultivation of rice with N2 under submerged and N0 under moist required the highest and lowest cost of production respectively. 4.2.11 Gross return The data in the Table 14 showed that average gross return ranged from GH₵6010 to GH₵17785.3 across the treatment combinations. The highest gross returns (GH₵17785.3) were realized when rice was produced under submerged with N2 fertilizer application rate followed by N2 treatments under AWD water management which recorded gross returns of GH₵17618.3.Gross returns increased with increased N fertilizer application rate regardless of the water management regime. In relation to water management treatments, gross return varied in this order: submerged > AWD > moist. For interaction effect the lowest gross returns was observed in N0 with moist interaction. 4.2.12 Net profit The influence of water management and N fertilizer application rate on net profit is indicated in Table 14. Average net profit ranged from GH₵3065 to GH₵13926.7 across the treatment combinations. In all cases, net profit increased with increased N fertilizer application rate. The trend of net profit with regard to water treatments was AWD > submerged > moist. For interaction effect, the greatest interaction effect on net profit (GH₵13926.7) was N2 with AWD. Interaction effect of N0 with moist was inferior to other interaction effect of water management and N fertilizer 4.2.13 Benefit cost ratio The effect of water management and benefit cost ratio of rice production is presented in Table 14. Benefit cost ratio ranged from 1.04 to 3.77 across the treatment combinations. During the field 70 University of Ghana http://ugspace.ug.edu.gh experiment, N fertilizer on benefit cost ratio was ranked as: N2 > N1 > N0. In relation to water management, the trend was AWD > submerged > moist. The interaction effect of N2 with AWD gave the greatest benefit cost ratio. The lowest benefit cost ratio (1.04) was produced at N0 with moist interaction. Table 14: Cost of production, gross returns, net profit and benefit cost ratio as influenced by water management and N fertilizer Cost of Gross Net Benefit cost Treatment production(GH₵/ha) returns(GH₵/ha) profit(GH₵/ha) ratio Water (W) AWD 3469.4 12811.1 9341.7 2.64 Moist 3213.3 9214.9 6004.4 1.83 Submerged 3688.2 12898.4 9170.6 2.41 N Fertilizer (N) N0 3206.2 7443.9 4238.0 1.31 N1 3513.3 11615.8 8102.4 2.30 N2 3688.2 15864.8 12177 3.28 Interaction AWD×N0 3206.7 8064 4858.0 1.52 AWD×N1 3510 12750 9240.0 2.63 AWD×N2 3691.7 17618.3 13927.0 3.77 Moist×N0 2945 6010.0 3065.0 1.04 Moist×N1 3266.7 9444.0 61773.0 1.89 Moist×N2 3419.7 12190.7 8771.0 2.56 submerged×N0 3467 8257.0 4790.0 1.38 submerged×N1 3763.3 12653.3 8890.0 2.36 submerged×N2 3953.3 17785.3 13832.0 3.50 Submerged is continuous submergence; AWD is alternate wet and dry; N0, N1 and N2, are 0, 60 and 90 kg N ha-1 respectively. 71 University of Ghana http://ugspace.ug.edu.gh CHAPTER FIVE DISCUSSION 5.1 Plant growth Results from both the pot and field experiments showed that, plant height, biomass accumulation and leaf area index increased from active tillering till harvest. Tillering on the hand, increased up to maximum tillering stage and thereafter declined gradually till harvest. The decrease in tillering of rice could be attributed to the death of some of the last tillers as a result of their failure to compete for light and available nutrients (Fageria, et al., 1997). Further explanation for this observation might be that during the panicle initiation stage, competition for assimilates existed between developing panicles and young tillers. Consequently, growth of many young tillers were suppressed, which might have led to tiller senescence. Similar observations were made by Dofing and Karlsson (1993). 5.1.1 Effect of N fertilizer on plant growth In both experiments, application of N fertilizer influenced vegetative growth significantly. Application of N1 and N2 enhanced the growth of plants better than the unfertilized plants. Probably low level of native N in the soil may explain the poor growth of rice in the unfertilized plants compared with N treated plant under same water treatments. The increased in vegetative growth with N fertilization might be due to the effective role of nitrogen in vegetative growth which enhanced the overall growth and physiology of rice (Snyder and Slaton, 2002). The result obtained agrees with that reported by El-wahab et al. (2007) and Khairi et al. (2015) who observed that application of nitrogen fertilizer usually produce more vegetative growth than plant treated with no N fertilizer. Also, increased biomass accumulation and LAI with increased N fertilizer rate might be due to the effectiveness of photosynthesis of the crop which depends on large and efficient assimilating area for adequate supply of solar radiation and carbon dioxide (Reddy and Reddi, 2002). 72 University of Ghana http://ugspace.ug.edu.gh These results are in agreement with Rezaei et al. (2009) who reported that increasing fertilizer nitrogen rate increases dry matter accumulation in rice crop by promoting nitrogen uptake. Ye et al. (2013) also stated that increased dry matter could be attributed to increase in length, number of tillers, elongation of stem and panicles. Similarly, Pradhan et al. (2013) reported that, application of nitrogen promotes rapid growth through increasing plant height, improve tillering and leaf area index. At flowering, leaf chlorophyll content of plants treated with higher N rate was higher than those that received lower N rate and no N application. The higher chlorophyll content in the treatment could be attributed to increased availability of nitrogen which essential for chlorophyll formation to the plants as reported by Kingori (2016). 5.1.2 Effect of water management on plant growth Plants under submerged had the highest vegetative growth. This could be due to the higher nutrient availability to plant roots as a result of the adjustment of soil pH to neutral range as observed by Ponamperuma (1984). Saharawat (2012) reported an improvement in availability of micro and macro nutrients such as nitrogen, phosphorus, potassium, magnesium and silicon under submerged soil condition. Plants treated under AWD water treatment produced vegetative growth similar to the submerged treatments. This could be due to the fact that AWD treatment does not restrict water availability to rice plant roots (Belder et al. 2004). Also it could be due the fact that AWD promotes root growth as result of air exchange between the atmosphere and the soil (Tan et al., 2013). Moist treated plant showed poor growth due to low moisture availability. In low water condition plant cannot absorb nutrients from the soil efficiently due to insufficient moisture, consequently crop growth became stunted (Mannan et al., 2012). Also, biomass accumulation and leaf area index (LAI) decreased with moist water condition. Reduction in plant growth could be attributed to the reduction in plant height, tillering and death of the lower leaves which could have been affected 73 University of Ghana http://ugspace.ug.edu.gh by low moisture condition. This finding is in line with Andreas and Karen (2002) who reported that reduced soil moisture at vegetative stage of rice decreased growth and development of foliage. This observation as explained by Sabbor et al. (2007) is attributed to the fact that cumulative effect of water stress on plants grown under moist water management is similar to plants stressed early in crop development resulting in reduced leaf area index. Light interception and carbon assimilation are reduced and hence the rate of leaf development and expansion reduces. Furthermore, relatively low available soil moisture which characterizes moist treated plants might lead to reduction of cell division and enlargement of different plant tissues which in turn depressed the vegetative growth and dry matter accumulation (Sabbour et al., 2007). These results are in agreement with those obtained by El-wahab et al. (2007) who found a reduction in leaf area index and biomass accumulation due to reduced soil moisture level. 5.1.3 Interaction effect of water and N fertilizer on plant growth Interaction effect of N2 with AWD resulted similar plant growth with N2 under submerged water management. The observed results could be attributed to availability of adequate moisture and nutrient for plant growth. Similar results were reported by Belder et al. (2004). Furthermore, Tan et al. (2013) revealed that AWD promotes root growth and nitrogen uptake due to gaseous exchange between the soil and the atmosphere. Plants under moist water management (N) without fertilizer showed poor growth. This confirms a report by Akram et al. (2013) who found out that plant growth reduced when water stress was imposed during panicle initiation stage of rice. 74 University of Ghana http://ugspace.ug.edu.gh 5.2 Effect of N fertilizer on yield and yield parameters Plants fertilized with nitrogen had higher grain yield than unfertilized plants due their higher grains/panicle and panicles/m2. Split application of nitrogen fertilizer at transplanting and panicle initiation stage ensured efficient use of fertilizers. This results agrees with Witt et al.(2002) who observed that nitrogen fertilizer application increased the activity of cell division and expansion of rice which enhanced grain yield. Also, Cabangon et al. (2011) observed that N fertilizer helps in efficient mobilization of resources and photosynthesis for the purpose of grain filling. N2 had higher rice yield and yield parameters than N1 and it might be attributed to its contribution to higher number of panicle/m2, grains/panicle and panicle length. This could also be due to its higher availability of nitrogen which might have resulted in higher grains/panicle and panicles/m2 and consequently led to higher yields than N1. Similar reports were made by Singh and Pillai (1994), Mannan et al. (2012) and Azarpour et al. (2014) who all observed that the application of 90 kg/ha N increased rice yield significantly. The finding however, are contrary to report by Rezaei et al. (2009) in which application of nitrogen fertilizer above 60 kg N ha-1 did not improve yield significantly. Nitrogen fertilization did not significantly influence 1000 grain weight of rice. This might be due to the fact that 1000 grain weight is a genetic trait strictly controlled by the hull of a particular variety and therefore cannot grow above the size allowed by the size of the hull (Mae, 1997). 5.3 Effect of water management on yield and yield parameters of rice In both experiments, differences in yield and yield parameters between AWD and submerged was not statistically significant. Similar observation was made by Belder et al. (2004), who argued that AWD does not restrict water availability to rice plant. This also explains the fact that, during AWD, water table was within the root zone of the plant and therefore the drying period may not 75 University of Ghana http://ugspace.ug.edu.gh sufficiently expose the rice plant to water stress to give comparable rice yield as with continuously submerged conditions (Guerra et al., 1998). Also, Plant adopts osmotic adjustment at the vegetative stage which contributes the mostly noticeable mechanism of dehydration tolerance in the rice plant, though any drought stress at early reproductive phase can cause great loss (Subramanian 2008). Since AWD plots were submerged at booting stage till ten days before harvest, no yield penalties were recorded. Rezaei et al. (2009) observed that continuous submergence of rice fields does not significantly increase yield over AWD. The results from this study is consistent with previous studies by Tuong (2003) , Mannan et al. (2012) and Khairi et al. (2015) who all observed similar grain yield between AWD and submerged treatments. However, Bouman and Tuong (2001) and Belder et al. (2004) observed higher panicle/m2 and grain yield under AWD. Harbir et al. (1991), Marazi et al. (1993), and Awad (2001) however reported that, AWD reduced grain yield significantly. The different in responses of water can be attributed to different soil types, rice variety, climatic conditions as well as duration of irrigation (Belder, 2004). Plants grown under moist water management had significantly lower grain yields. This also could be due to poor metabolism as a result of its reduced water availability and therefore led to reduction in grain yields. Furthermore, reduced yields under moist soil condition might be due to inhibition of photosynthesis and less translocation of assimilates due to soil low moisture availability (Tabbal et al., 2002). Results from this current study are similar to those reported by Mannan et al.(2012) who observed reduction in number of grains panicle-1 and shorter panicles due to less soil moisture. According to Akram et al. (2013) water stress at flowering stage reduced percentage of filled grains and 1000 grain weight significantly. Since all the water treatments in both field and pot experiments were submerged from booting stage to ten days before harvest, there was no water 76 University of Ghana http://ugspace.ug.edu.gh stress at flowering stage and therefore water management treatments did not significantly affect 1000 grain weight and percentage filled grains. 5.4 Interaction effect of water and N fertilizer on yield and yield parameters Interaction effect of N2 with AWD had similar yield as in submerged and N2 treatment combination as both resulted in similar panicle length, grains/panicles and panicles/m2. This observation might also be attributed to more nitrogen being transported to the plant when plants were treated with higher doses of N. Overall N0 under moist treatment combination gave the lowest grain yield due reduced moisture level at panicle initiation stage. (Akram et al., 2013) reported similar observation. 5.5 Effect of N fertilizer on N uptake and nitrogen use efficiency N-uptake in both grain and straw increased with increased nitrogen rates across the treatments. N2 had the highest N uptake and agronomic nitrogen use efficiency (ANUE) as a result of higher above ground biomass accumulation and larger leaf area index. Large leaf area index results in higher rate of transpiration and consequently increase nitrogen uptake by plant roots (Haefele et al., 2008). Kumar and Rao (1992) and Panda et al. (1996) also reported that the uptake of N by rice crop and concentration in the tissues increased by increased N rate. Reduced N uptake in N0 might be due its lower transpiration rate as a results of its small leaf area index and reduced aboveground biomass. This assertion is given credence by earlier reports by De wit (1958) who reported that lower transpiration rate reduced biomass accumulation and consequently lower nitrogen uptake by plant. 5.6 Effect of water management on N uptake, ANUE and PNUE of rice Submerged water treatment had the highest N uptake and ANUE due to higher availability of nitrogen. According to Ponamperuma (1984) unavailable nutrients become available to plant under 77 University of Ghana http://ugspace.ug.edu.gh submerged condition due to the adjustment of soil pH to neutral range. In addition submerged condition improves the delivery of nutrients to plant roots through mass flow and diffusion mechanisms (Ponamperuma 1984). Ye et al. (2013) who reported that N uptake increased when plants were grown under submerged water management regime. AWD treatment had similar N uptake and ANUE because AWD creates aerobic conditions which enhance root growth and therefore better surface area for uptake of nutrients. According to Reddy and Reddi, (2002) nutrient uptake by plants largely depends on the increment of the nutrient ion to the absorbing root surface or on the roots’ ability to reach the zone of nutrient availability. The results from the study agrees with the studies conducted by Belder et al. (2005) who observed that nitrogen use efficiency (NUE) in AWD water management was not significantly different from submerged condition. The study however disagrees with Zare et al. (2014) who found NUE to be significantly higher in AWD water management than submergence condition. Moist treatment was statistically inferior due its smaller leaf area index which limits N uptake possibly as a result of lower transpiration rate. This agrees with Haefele et al. (2008) who reported that small leaf area index reduced transpiration rate and therefore decreased nitrogen uptake by plant roots. It can also be due to reduced soil moisture from crop establishment to booting stage which might have reduced N uptake by rice roots. 5.7 Interaction effect of water and N fertilizer on N uptake and NUE Interaction effect of submerged water management with N2 rate gave higher N uptake. This can be due to its higher aboveground biomass accumulation compared with the other treatment combinations. Moist with N0 interaction gave the lowest N uptake and NUE due to its lower leaf area index. These are in line with Haefele et al. (2008) who revealed that small leaf area index reduced transpiration rate and therefore decreased nitrogen uptake by rice plant. 78 University of Ghana http://ugspace.ug.edu.gh 5.8 Effect of N fertilizer on water use and water productivity of rice From both experiments, higher water productivity with N2 treatment than the other treatments can be associated with its higher grain yield. Pandey et al. (2001) reported that, N fertilization increased water productivity due to increased yield than unfertilized plants. The lower water productivity in N0 was due to reduced yields as a results of grains/panicle and panicle per m2. N2 had the highest water use due to its higher transpiration rate as results of it higher vegetative growth. Mannan et al. (2012) observed that vegetative growth as a result of higher photosynthesis and metabolism led to more water requirement by plants in order to carry out their physiological functions. Lower water use in N0 could be attributed to less water loss through transpiration as a result of its lower leaf area index. This is in line with Song et al. (2010) who observed that large leaf area index results in higher water loss through transpiration. 5.9 Effect of water management on water use and water productivity Comparing the different treatments of water management in both trials, it was observed that submerged water management received higher amount of water use than AWD and moist treatments due to the standing water layer maintained continuously on the plot from crop establishment till ten days to harvest. According to Odhiambo and Murthy (1996) evapotranspiration was intense under continuous submergence including evaporation of free water from the standing pool of water. This probably increased the rate of evapotranspiration and percolation in submerged treatments which in turned increased water requirement. However, AWD had higher water productivity than submerged treatment due to its lower water use. This finding is in agreement with Tabbal et al. (2002), Belder et al. (2004), Kato et al. (2009). Wardana et al. (2010) observed that AWD resulted in higher water productivity than continuous submergence of fields. Also Talpur et al. (2013) reported that, continuous submergence produced 79 University of Ghana http://ugspace.ug.edu.gh optimum rice yield however, required the highest amount of water hence low water productivity. Moist treatment had the lowest water use and higher water productivity due to the absence of standing water layer from one week after transplanting to booting stage. This conforms to Dahmardeh et al. (2015) who reported that reduction in water use increased water productivity of rice. 5.10 Interaction effect of water management and N fertilizer on water use and water productivity Interaction effect of N2 and submerged water management required higher water use due to higher evapotranspiration rate as a result of its higher leaf area index and evaporation of free water from the standing pool of water (Odhiambo and Murthy 1996). With regards to water productivity, N2 treated plants under moist water condition gave higher water productivity compared to the rest of the treatment combinations due to its lower water use. Dahmardeh et al. (2015) who reported that reduction in water use increased water productivity of rice. 5.11 Cost-effectiveness of water use under various water management methods The economic analysis from the study revealed that, it was highly economical to produce rice under AWD than the rest of the water management treatments. Although grain yields and gross returns were higher under submerged treatments than AWD water management, cost associated with water under submerged water management reduced net profit since general cost of production was same for all the water treatments. Moist treatment had the highest water productivity but the lowest gross returns due to reduced yields. The outcome agrees with the assertion by Barker et al. (2002) and Visperas, et al.(2005) who argued that, an increase in water productivity may not result in higher economic benefits. Despite the fact that gross returns was higher in submerged water 80 University of Ghana http://ugspace.ug.edu.gh management than AWD water management, it’s economic water use was the least compared to AWD at any given N rate due to significant water cost associated with this water management regime. Ganiyu, et al.(2015) suggested that, continuous submergence and maintaining moisture level at field capacity does not increase crop and economic water productivity. 81 University of Ghana http://ugspace.ug.edu.gh CHAPTER SIX CONCLUSIONS AND RECOMMENDATIONS 6.1 Conclusions Water and nitrogen are the two most important factors for increased rice growth, yield, nitrogen uptake and water productivity in irrigated rice farming system. On the basis of the findings, the following conclusions can be drawn:  Application of N fertilizer positively influenced rice growth and yields with highest yields observed in application of 90 kg/ha.  AWD resulted in similar growth and yields compared to submerged water treatments. Growth and yield of rice were better with interaction effect of 90 N kg/ ha and submerged.  Nitrogen uptake increased with increased N fertilizer rate and application of 90 N kg/ha gave higher uptake. N uptake in AWD was at par with uptake in submerged water treatment but lower in moist water management.  Water productivity was higher under moist water management due to the less amount of water required.  AWD required less water than continuous submergence for rice production and it was cost effective to produce rice under AWD over the rest of the water management methods. 82 University of Ghana http://ugspace.ug.edu.gh 6.2 Recommendation  AWD and 90 kg N/ha combination holds promise and seem to be better option to efficiently manage water and N fertilizer where water availability at the farm level is too low, or where water is too expensive to grow irrigated rice.  The research is one-season one-location experiment. It needs to be repeated with time and locations to increase the validity of the findings made.  Further studies should be conducted on nutrient requirement of irrigated rice under different soil types and agro ecological zones.  The response of different varieties of rice should also be investigated under the various water management and N fertilizer levels used in the experiment. 83 University of Ghana http://ugspace.ug.edu.gh REFERENCES Abdul-Ganiyu, S.1., Kyei-Baffour, N. , Agyare, W and Dogbe, W. (2015). Effect of Irrigation Regimes on Irrigated Rice Production in the Northern Region of Ghana. International Journal of Agriculture Innovationss and Research, 1(1):129–143. Abou-khalifa, Ali A. B. (2012). Evaluation of some rice varieties under different nitrogen levels. Advances in Applied Science Research, 3(2):1144–1149. Aguilar, M., & Borjas, F. (2005). Water use in three rice flooding management systems under Mediterranean climatic conditions. Spanish Journal of Agricultural Research, 3(3): 344–351. Angelucci F., Asante-Poku A. and Anaadumba P., (2013). Analysis of incentives and disincentives for rice in Ghana. Technical notes series, MAFAP, FAO, Rome. Akram, H. M., Ali, A., Sattar, A., Rehman, H. S. U. and Bibi, A. (2013). Impact of water deficit stress on various physiological and agronomic traits of three basmati rice (Oryza sativa L.) cultivars. The Journal of Animal and Plant Sciences, 23(5): 1423–1455. Ali MH, Talukder MSU. (2008). Increasing water productivity in crop production a synthesis. Agricultural Water Management, 95: 1201–1213. Anchal D and Shiva D. (2014). Irrigation Management for Improving Productivity Nutrient Uptake and Water-Use Efficiency in System of Rice Intensification: A Review,32 (2):108– 122. Andreas P.S. and Karen F. (2002). Crop Water Requirement and Irrigation Scheduling. Irrigation Manual 4. Harare Andriesse, W. and Fresio, L.O. (2009). A characterization of rice growing environment in West Africa. Agricultural Ecosystems Environment, 33:337-395. Awad (2001). Rice production at the north of Delta region in Egypt as affected by irrigation intervals and nitrogen fertilizer levels. Journal of Agricultural Science, Mansoura University, 26(2):1151-1159. Azad A. K., Faffar M.A., Samanta C.M. Kashem M.A. and Islam M.T. (1995). Response of BR 10 rice to different levels of nitrogen and spacings. Bangladesh Journal of Science, 30(1):31- 38 Azarpour E., Moraditochaee M., and Bozorgi, H. R. (2014). Effect of nitrogen fertilizer management on growth analysis of rice cultivars. International Journal of Biosciences, 4: 35– 47. Barker, R. and Molden, D (1990). Water productivity in agriculture: limits and opportunities for improvement. pp. 239-253. CABI Publishing, Wallingford UK. 84 University of Ghana http://ugspace.ug.edu.gh Barker, R, Dawe, D and Inocencio, A. (2003). Economics of water productivity in managing water for agriculture. Limits and Opportunities for Improvements. (Eds. J.W.Kinje, R. Barker and D.Molden), 19-36, (CABI, Oxford) Basorun, J. O. (2003). Analysis of the relationships of factors affecting rice consumption in a targeted region in Ekiti-State, Nigeria. Journal of Applied Quantitative Methods, 4 (2): 145- 153. Belder, P., Bouman, B. A. M., Cabangon, R., Guoan, L., Quilang, E. J. P., Yuanhua, L.,Tuong, T. P. (2004). Effect of water-saving irrigation on rice yield and water use in typical lowland conditions in Asia. Agriculture water Management, 65: 193–210. Belder, P., Spiertz, J. H. J., Bouman, B. A M., Lu, G., and Tuong, T. P. (2005). Nitrogen economy and water productivity of lowland rice under water-saving irrigation. Field Crops Research, 93(2-3):169–185. Berisavljevic, G. K., Blench, R. M., and R. Chapman. (2003). Some Features of Rice Production in Ghana. Available on line at http//www.odi.org/resources/downloaded/3159.pdf. Accessed 09/24/09. Blumenthal, J. D. M., Baltensperger, D. D., Cassman, K. G., Mason, S. C., and Pavlista, A. D. (2008). Importance and Effect of Nitrogen on Crop Quality and Health. Nitrogen in the Environment, 51–70. Boonjung, H. and S. Fukai, (1996). Effects of soil water deficit at different growth stages on rice growth and yield under upland conditions. Field Crops Research,48: 47-55 Borell, A., Garside, A., Fukai, S., (1997). Improving efficiency of water for irrigated rice in a semi- arid tropical environment. Field Crops Research, 52:231–248. Bouman, B.A.M., (2007). Rice: feeding the billions. In: Molden, D. (ed.). Water for food water for life: Comprehensive assessment of water management in agriculture. pp 515-549. International Water Management Institute, Colombo,Sri Lanka Bouman, B.A.M. and Tuong, T. P. (2001). Field water management to save water and increase its productivity in irrigated rice. Agricultural Water Management, 49: 11-30. Bouman B.A.M, Hengsdijk H, Hardy B, Bindraban PS, Tuong TP, Ladha H. K, (20002). Water- wise rice production. Proceedings of the International Work-shop on Water-wise Rice Production, 8-11 April 2002, Los Banos, Philippines. International Rice Research Institute 356p Bouman, B. A M., Yang, X., Wang, H., Wang, Z., Zhao, J., and Chen, B. (2006). Performance of aerobic rice varieties under irrigated conditions in North China. Field Crops Research, 97(1):53–65. 85 University of Ghana http://ugspace.ug.edu.gh Bouman, B. A. M., Lampayan, R. M., and Tuong, T. P. (2007). Water Management in Irrigated Rice: Coping with Water Scarcity. International Rice Research Institute. Bouman, B. A.M., Barker, R., and Humphreys, E. (2007). Rice: feeding the billions. In Water for Food, Water for Life, International Water Management Institute: Colombo, Sri Lanka, pp. 515–549. Buri, M. M., Issaka, R. N., Wakatsuki, T., & Kawano, N. (2012). Improving the productivity of lowland soils for rice cultivation in Ghana : The role of the “ Sawah ” system. Journal of Soil Science and Environmental Management 3(3):56–62. Cabangon, R. J., Castillo, E. G., & Tuong, T. P. (2011). Field Crops Research Chlorophyll meter- based nitrogen management of rice grown under alternate wetting and drying irrigation. Article in Fuel and Energy, 121(1):136–146. Cabuslay, G.S., O. Ito and Alejar A.A., (2002). Physiological evaluation of responses of rice (Oryza sativa L.) to water deficit. Plant Science, 163 : 815-827. Carney, J. (2000). The African origins of Carolina rice culture. Ecumene 7 (2): 125-149. Cassman K.G., De Datta, S. K.,Amarante, S.T., Liboon, S.P., Samson, M.I., Dizon, M.A.(1996). Long term comparison of the agronomic efficiency and residual benefits of organic and inorganic nitrogen sources for tropical lowland rice. Experimental Agriculture. 32: 427-441. Cassman K.G., S. Peng, D.C Olk, J. K. Ladha, W. Reichardt, A. Dobermann and U. Singh, (1998). Opportunities for increased nitrogen use efficiency for improved resources management in irrigated rice systems. Field Crops Research, 56: 7-39. Chander S and Pandey J. (1996). Effect of herbicide and nitrogen on yield of scented rice (oryza sativa) under different rice cultures. Indian Journal of Agronomy 41(2): 209-214. Chaturvedi, I., & Chaturvedi, I. (2005). Effect of nitrogen fertilizers on growth , yield and quality of hybrid rice ( oryza sativa ). Journal of Central European agriculture. 6(4), 611–618 Dahatonde, B. N. (1992). Response of promising prereleased rice (Oryza sativa L.) varieties to graded levels of nitrogen. Indian Journal of Agronomy, 37(4): 802-803. Dahmardeh K, Rad MRP, Rad MRN, Hadizadeh M. (2015). Effects of potassium rates and irrigation regimes on yield of forage sorghum in arid regions. International Journal of Agronomy and Agricultural Research 6(4): 207-212 De Datta, S. K.(1981). Principles and practices of rice production. Sementara, 642. De Datta S. K.(1986). Producción de arroz. Ed. Mundi-Prensa, 690 p. De Datta, S. K. (1995). Nitrogen transformations in wetland rice ecosystems. Fertilizer Research, 86 University of Ghana http://ugspace.ug.edu.gh 42: 193 – 303. David, C.C. (1991). The world rice economy: challenges ahead. In G.S. Khush and H.T. Gary,eds. Rice biotechnology ,pp 1-18. Los Banos, Philippines, International Rice Research Institute (IRRI). (Biotechnology in Agriculture No. 6) De Wit, C. T. (1958). Transpiration and crop yields. Versl. Landbouwk. Onderz., Institute of Biological and Chemical Research on Field Crops and Herbage, Wageningen, The Netherlands. 64, 6. Dawe, D., Dobernmann, A., Moya, P., Abdurrahman, S., Singh Bijay, Lal, P., Li, S.Y., Lin, B., Panaullah, G., Sariam, O., Singh, Y., Swarup, A., Tan, P. S. and Zhen, Q.,X. (2000). How widespread are yield declines in long-term rice experiments in Asia? Field Crops Research, 66:175-193. Dikshit P.R. and Paliwal AK., (1989). Effect of Nitrogen and Sulphur on the yield and quality of rice. Agricultural Science Digest. 9:171-174. Dobermann, A. and T. Fairhurst. (2000). Rice nutrient disorders and nutrient management. International Rice Research Institute, Manila, Philippines. Dofing, S. M. and M. G. Karlsson. (1993). Growth and development of uni-culm and conventional tillering barley lines. Agronomy Journal 85: 58–61. Duhan, B. S and Singh, M. (2002). Journal of Indian Society of Soil Science, Vol. 50(2): 178-180 Dunn, B. W., and Gaydon, D. S. (2011). Rice growth, yield and water productivity responses to irrigation scheduling prior to the delayed application of continuous flooding in south-east Australia. Agricultural Water Management, 98(12):1799–1807. El-wahab, A. E., Mahrous, F. N., and Ghanem, S. A. (2007). Irrigation management and splitting of nitrogen application as affected on grain yield and water productivity of hybrid and inbred rice. Journal of Agriculture, Mansoura University. 8(1990): 45–52. Fageria, N. K., A. B. Santos and V. C. Baligar.(1997). Phosphorus soil test calibration for lowland rice on an Inceptisol. Agronomy Journal 89: 737– 742. Fageria, N. K., Slaton, N.A. and Baliges,V.C. (2011). Nutrient management for improving lowland rice productivity and sustainability. Advances in Agronomy, 80: 63-152. FAO (1986). Yield Response to Water. Irrigation and Drainage paper No 33. Rome. FAO. (2004). Food and Agriculture Organization of the United Nations. FAOSTAT statistics data- base-agriculture, Rome, Italy. 87 University of Ghana http://ugspace.ug.edu.gh FAO. (2005). Food and Agricultural Organization Statistics Book on National Crop Production. Rome, Italy. pp. 89. FAO (2007). Review of global agricultural water use per country. Aquastat, FAO's information system on water and agriculture. FAO, Land and Water Development Division. FAOSTAT- Food and Agriculture Organization of the United Nations data (2012). Statistical databases. Available at http://faostat.fao.org/default.aspx?lang=en.Assessed on Feb. 20, 2015 George, T., Ladha, J. K., Buresh, R. J., and Garrity, D. P. (1992). Managing native and legume- fixed nitrogen in lowland rice-based cropping systems. Plant and Soil, 141(1-2):69–91. Gonzalez-dugo, V., Durand, J., Gonzalez-dugo, V., and Durand, J. (2010). Water deficit and nitrogen nutrition of crops . A review To cite this version : Review article. Gu, Y., Zhang, X., Tu, S. and Lindstrom, K. (2009). Soil microbial biomass, crop yields, and bacterial community structure as affected by long-term fertilizer treatments under wheat–rice cropping. European Journal of Soil Biology, 45: 239–246. Guerra, L. C., Bhuiyan, S. I., Tuong, T. P. and Barker, L. (1998). Producing more rice with less water from irrigated system. SWIM Paper 5. IWMI/IRRI, Colombo, Sri Lanka. Haefele, S. M., Jabbar, S. M. A., Siopongco, J. D. L. C., Tirol-Padre, A., Amarante, S. T., Sta Cruz, P. C., and Cosico, W. C. (2008). Nitrogen use efficiency in selected rice (Oryza sativa L.) genotypes under different water regimes and nitrogen levels. Field Crops Research, 107(2):137–146. Hari, O, S. K. Kayal, S.D. Dhiman and H. Om (1999). Response of two rice (Oryza Sativa) hybrid to graded levels of nitrogen. Indian Journal of Agricultural Science, 70(3):140-142. Harbir, S., Singh, T., Singh, K.P. S., Tonk, D.S. and Faroda, A.S. (1991). Components analysis of yield to irrigation condition in rice. Naredra Deva Journal of Agriculture Research, 6(1):119- 123. Haque, A., & Haque, M. M. (2016). Growth , Yield and Nitrogen Use Efficiency of New Rice Variety under Variable Nitrogen Rates. American Journal of Plant Science. 2016(7)612–622. Hobbs, P., Gupta, R. K. (2003). Rice-wheat cropping systems in the Indo-Gangetic Plains: issues of water productivity in relation to new resource-conserving technologies. Water productivity in agriculture: limits and opportunities for improvement. 15:239 Hossain, M. A., Salahuddin, A. B. M., Roy, S. K., Nasreen, S. and Ali, M. A. (1995). Effect of green manuring on the growth and yield of transplant aman rice. Bangladesh Journal of Agricultural Science, 22(1): 21-29. Humphreys, E., Meisner, C., Gupta, R., Timsina, J., Beecher, H.G., Tang, Y.L. Thompson J.A. 88 University of Ghana http://ugspace.ug.edu.gh (2005). Water saving in rice-wheat systems. Plant Production Science, 8(3):242-258. Husan, M. R., Islam, M. R., Faried, K., & Mian, M. H. (2014). Nitrogen use efficiency and rice yield as influenced by the application of prilled urea and urea super granule with or without organic manure. Journal of Bangladesh Agricultural University 12(1):37–43. Hussain, S. M. and Sharma, U. C. (1991). Response of rice to nitrogen fertilizer in acidic soil of Nagaland. Indian Journal of Agricultural Science. 61(9): 660-664. Idris, M. and Matin, M. A. (1990). Response of four exotic strains of aman rice to urea. Bangladesh Journal of Agricultural. Science, 17(2): 271-286 International Rice Research Institute (IRRI). (2008). Rice knowledge bank. Rice Doctor- Growth stages and important management factors. http://www.knowledgebank.irri.org/RiceDoctor/ default.htm. Islam, M. R., Haque, M. S. and Bhuiya, Z. H. (1990). Effect of nitrogen and sulphur fertilization on yield response and nitrogen and sulphur composition of rice. Bangladesh Journal of Agricultural Science 17(2): 299-302. Jamil, M., and Hussain, A. (2000). Effect of different planting methods and nitrogen levels on growth and yield of rice (basmati·385). Pakistan Journal of Agricultural Science. 37, 83–85. Jing, Q., Dai, T., Jiang, D., Zhu, Y., & Cao, W. (2007). Spatial Distribution of Leaf Area Index and Leaf N Content in Relation to Grain Yield and Nitrogen Uptake in Rice. Plant Production Science, 10(1): 136–145. Juraimi, A. S., Muhammad Saiful, A. H., Begum, M., Anuar, A. R., & Azmi, M. (2009). Influence of Flooding Intensity and Duration on Rice Growth and Yield. Pertanika Journal of Tropical Agricultural Science, 32(2): 195–208. Kadigi R.M.J (2003). Rice Production Economics at the Local and National Levels: The Case of Usangu Plains in Tanzania; unpublished document Kato, Y., Okami, M. and Katsura, K. (2009). Yield potential and water useefficiency of aerobic rice (Oryza sativa L.) in Japan. Field Crops Research, 113: 328–334. Karres, R., Sandra J.R, and Fernandez, R (1999). Effect of nitrogen rates on rice growth and biological fixation. Field Crops Research. 50:1-6 Khairi, M., Nozulaidi, M., Afifah, A., and Jahan, S. (2015). Effect of various water regimes on rice production in lowland irrigation. Australian Journal of Crop Science. 9(2):153–159. Khanda C. M and L. Dixit, (1996). Effect of zinc and nitrogen fertilization and yield and nutrient uptake of summer rice (Oryza sativa). Indian Journal of Agronomy, 41:368-372 89 University of Ghana http://ugspace.ug.edu.gh Khan, S., Tariq, R., Yuanlai, C., Blackwell, J., (2006). Can Iriigation be sustainable? Agriculture water Management 80:87-99. Kingori, G. G. (2016). Improving Seed Potato Leaf Area Index, Stomatal Conductance and Chlorophyll Accumulation Efficiency through Irrigation Water, Nitrogen and Phosphorus Nutrient Management. Journal of Agricultural Studies. 4(1):127 Kobata, T. and S. Takami. (1981). Effects of water stress during the early ripening period on the grain growth dry matter partitioning and grain yields in rice (Oryza sativa L.). Japanese Journal of Crop Science, 50: 536-545. Kukal, S. S., Sudhir-Yadav, Humphreys, E., Amanpreet-Kaur, Yadvinder-Singh, Thaman, S.,Timsina, J. (2010). Factors affecting irrigation water savings in raised beds in rice and wheat. Field Crops Research, 118(1):43–50. Kumar, D., Swarup, A. and Kumar, V. (1996). Influence of levels and methods of N application on the yield and nutrient uptake of rice in a sodic soil. Journal of Indian Society of Soil Science. 44(2): 259-263. Kumar, K.and K. V. P. Rao, (1992). Nitrogen and phosphorus requirement of upland rice in Manipur. Oryza. 29:306-309. Kumar Verma, Mukesh Mohan, Pramod K. Prabhakar, and Prm Prakash Srivastav (2015). Physico-chemical and cookingg characteristics of Azad basmati. International Food Research Journal 22(4):1380-1389 Khumbanyiwa A.G, Msuya, M.M, Boedts, B. and Mme. R. N. (2003). Multinational:Nerica Rice Dissemination Project. Retrieved from www.afdb.org/fileadmin Lawal, M. I. and Lawal, A. B. (2002). Influence of nitrogen rate and placement method on growth and yield of rice at Kadawa, Nigeria. Crop Res. Hisar. 23(3): 403-411. Li, J. (2003). The Natural History of Rice: Rice. In: Food and Culture Encyclopedia: The Gale Group, Inc. Li, H., & Li, M. (2010). Sub-group formation and the adoption of the alternate wetting and drying irrigation method for rice in China. Agricultural Water Management, 97(5):700–706. Mae, T. (1997). Physiological nitrogen efficiency in rice: Nitrogen utilization,photosynthesis, and yield potential. Plant Soil, 196: 201–210. Manzoor, Z., T.H. Awan, M.E. Safdar, R. Inayat, A. Mirza, M. Ashraf and M. Ahmad, (2006). Effects on nitrogen levels on yield and yield components of basmati rice. Journal of Agricultural Research, 44(2): 115-120. 90 University of Ghana http://ugspace.ug.edu.gh Maclean JL, Dawe D, Hardy B, Hettel GP, editors. (2002). Rice almanac. Los Baños (Philippines): International Rice Research Institute. 253 pp. Marazi, A.R., Khan, G.M., Sing, K.N. & Bali, A.S. (1993). Response of rice (Oryza sativa) to different nitrogen levels & water regimes in Kashmir Valley. Indian Journal of Agricultural Science, 63(11):726-727. Mardina Siti I. (2005). Kajian paras air berbeza ke atas populasi rumpai dan hasil padi. Final Year Project Paper, Universiti Putra Malaysia. 74p. Maske, N. S., Norkar, S. L. and Rajgire, H. J. (1997). Effects of nitrogen levels on growth, yield and grain quality of rice. Journal of Soils and Crops, 7(1): 83-86. Maskina, M. A., Khind, C. S. and Meelu, O. P. (1996). Organic manures as a nitrogen source in a rice-wheat rotation. International Rice Research. Newsletter. 11(5): 44. Malik, T. H., Lal, S. B., Wani, N. R., Amin, D., & Wani, R. A. (2014). Effect Of Different Levels Of Nitrogen On Growth And Yield Attributes Of Different Varieties Of Basmati Rice ( Oryza Sativa L). International Journal of Scientific and Technology Research. 3(3):444-448 Mannan, M. A., Bhuiya, M. S. U., Akhand, M. I. M., & Zaman, M. M. (2012). Growth and Yield of Basmati and Traditional Aromatic Rice As Influenced By Water Stress and Nitrogen Level. Journal of Science Foundation. 10(2): 52–62. Martens, D. A. (2001). Nitrogen cycling under different soil management systems. Advances in Agronomy, 70, 143-192. MOFA (2009) “Evaluation of the Ghana Rice Campaign”; A marketing campaign implemented by Engineers Without Borders and the Ghana Ministry of Food and Agriculture to stimulate the rice value chain, April 2009 MOFA (Ministry of Food and Agriculture) (2010): Agriculture in Ghana: Facts and Figures. Statistics, Research and Information Directorate (SRID), Ministry of Food and Agriculture, Accra, Ghana. Molden, D. (1997). Accounting for water use and productivity. SWIM Paper 1, International Irrigation Management Institute, Colombo, Sri Lanka. 16 p. Moutonnet,P., (2002). Yield response factors of field crops to deficit irrigation International Atomic Energy Agency, Joint FAO/IAEA Division, Vienna, Austria; In Deficit irrigation practices of FAO water report 22. Murty, P. S. S., Ramesh, K. S., Rao, G. V. H. and Narayanan, A. (1992). Influence of nitrogen on grain filling potential and yield of rice varieties. Indian Journal of Agronomy 37(1): 175-178. 91 University of Ghana http://ugspace.ug.edu.gh Nangia, V., de Fraiture, C., and Turral, H. (2008). Water quality implications of raising crop water productivity. Agricultural Water Management, 95(7), 825–835 Nakano Y., Bamba I., Diagne A., Otsuka K., and Kajisa K.(2011). "The Possibilities of a Rice Green Revolution in Large-Scale Irrigation Schemes in Sub-Saharan Africa.”Policy Research Working Paper, #5560 for the World Bank Agriculture and Rural Development Team. Nguyen, H. T., Fischer, K. S., and Fukai, S. (2009). Physiological responses to various water saving systems in rice. Field Crops Research, 112(2-3): 189–198. Normile, D. (2004). Yangtze seen as earliest rice site. Science 275: 309 Nour M.A., El-Wahab A.E. and Mahrous F.N., (1994). Effect of water stress at different growth stage on rice yield and contributing variables. Rice Research and Training Center. 1996. Annual Agronomy Report Odhiambo, L. O. and Murthy, V. V. N. (1996). Modelling water balance components in relation to field layout in lowland paddy fields. Agricultural water management, 30:185–199. Olk, D. C. and Senesi, N. (2000). Properties of chemically extracted soil organic matter in intensively cropped lowland rice soils. In: Kirk, G. J. D. and Olk, D.C. (eds.). Carbon and nitrogen dynamics in flooded soils. pp 65 – 87. International Rice Research Institute, Makati City, Philippines. Otsuka, K. and Yoko, K. (2010). “Technology Policies for a Green Revolution and Agricultural Transformation in Africa.” Journal of African Economies, 19(2): 60 – 96 Panda, M. M., Mahapatra, P. and Mohanty, S. K. (1996). Effect of depth of application of 15N tagged urea on its utilization efficiency by irrigated rice. Journal of Indian Soc. Soil Sci. 44(2): 233 235. Pandey R, Maranville J, Admou A. (2001). Deficit irrigation and nitrogen effects on maize in a Sahelian environment: Grain yield and yield components. Agriculture Water Management 46: 1-13 Patel, S. R. and Mishra, V. N. (1994). Effect of different forms of urea and levels of nitrogen on the yield and nitrogen uptake of rice. Advance Plant Science. 7(2): 397-401. Pirmoradian, N. and A.R. Sepaskhah, (2006). A very simple model for yield prediction of rice under different water and nitrogen applications. Biosys. Engineering. 93(1): 25-34. Ponnamperuma, F. N. (1984). Effect of flooding on soils. In: kozlowski T, editor. Flooding and plant growth. New York: Academic Press. p. 9-45. Ponnamperuma, F. N. (1985). Chemical kinetics of wetland rice soils relative soil fertility’, In: Wetland soils: characterization, classification, and utilization. pp 71-80. International Rice 92 University of Ghana http://ugspace.ug.edu.gh Research Institute (IRRI), Los Banos, Laguna, Philippines. Portères, R. (1956). Taxonomic agrobotanique des riz cultives. Journal d’Agriculture Tropicale et de Botanique, 3:341-856. Pradhan S., Chopra UK., Bandyopadhyay, KK., Singh, R., Jain AK. and Ishwar C. (2013). Effect of Water and Nitrogen Management on Water Productivity and Nitrogen Use Efficiency of Wheat in a Semi-arid Environment. International Journal of Agriculture and Food Science Technology, 4(7): 727-732 Raju, R. A. and Reddy, K. A. (1992). Response of winter rice (Oryza sativa) to nitrogen, phosphorus and potassium fertilization on Godawari alluvials. Indian Journal of Agronomy 38(4): 637-638. Ramamoorthy, K., Selvarao K. V. and Chinnaswami, K. N. (1993). Varietal response of rice to different water regimes. Indian Journal of Agronomy 38: 468-469. Ramasamy, S., H. F. M. ten Berge, and S. Purushothaman (1997). Yield formation in response to drainage and nitrogen application. Field Crops Research, 51: 65-82. Ravenga, C., Brunner, J., Henninger, N., Kassem, K. and Payne, R. (2000). Pilot Analysis of Global Ecosystems: Wetland ecosystems. World Resources Institute, Washington, DC Reddy, T. Y. and Reddi, G. H. (2002). Principles of agronomy (3rd Ed.). Kalyani Publishers, New Delhi, India. 526 p. Rejesus, R. M., Palis, F. G., Gracia, D., Rodriguez, P., Lampayan, R. M., and Bouman, B. A. M. (2011). Impact of the alternate wetting and drying ( AWD ) water-saving irrigation technique : Evidence from rice producers in the Philippines. Food Policy, 36(2):280–288. Rezaei, M., Vahed, H. S., Amiri, E., Motamed, M. K., & Azarpour, E. (2009). The Effects of Irrigation and Nitrogen Management on Yield and Water Productivity of Rice. World Applied Sciences Journal. 7(2): 203–210. Ritesh S, Raveesh K G. Vivek Y. and Raksh K. (2014). Response of Basmati rice (Oryza sativa) cultivars to graaded nitrogen levels under transplanted condition. International Journal of Research in Applied, Natural and Social Sciences (Impact: Ijranss), 2(9):33–38. Russo, S. (1996). Rice yield as affected by the split method of N " application and nitrification inhibitor DCD, Research paper. 52(1):43–52. Sabbour M.M, Abd El-Aziz ShSI W. (2007).Efficiency of some bioinsecticides against broad bean beetle, Bruchus rufimanus (Coleoptera Bruchidae).Research Journal of Agriculture and Biological Science, 3(2): 67-72 93 University of Ghana http://ugspace.ug.edu.gh Saharawat, K. L. (2012). Soil fertility in flooded and non-flooded irrigatted rice systems. Archives of Agronomy and Soil Science, 58(4): 423-436. Sariam, O. (2004). Growth of non-flooded rice and its response to nitrogen fertilization. PhD Thesis. Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia. Saied, M. M., & Zoghdan, M. G. T. (2012). Impact of intermittent irrigation and nitrogen fertilization on yield of rice ( orayza sativa L .) and some water relations. Journal of Soil Science and Agriculture, England, Mansoura University 3(10): 985–1000. Shabbir, M. A., Anjum, F. M., Zahoor, T. and H. Nawaz. (2008). Mineral and Pasting Characterization of Indica Rice Varieties with Different Milling Fractions. International Journal of Agriculture and Biology, 10: 556-560. Shirazi, S. M., Yusop, Z., Zardari, N. H., & Ismail, Z. (2014). Effect of Irrigation Regimes and Nitrogen Levels on the Growth and Yield of Wheat. Advances in Agriculture. 2014(2014):1- 6 Shpilyov, A. V., Vladislav, V. Z., Bernhard, G., and Lokstein, H. (2013). Chlorophyll a phytylation is required for the stability of photosystems I and II in the cyanobacterium Synechocystis PCC 6803. The Plant Journal 73:336-346. Singh, S., Sing, M. P., Bakshi, R., (1990). Unit energy consumption for paddy-wheat rotation. Ener. Conver. Manage. 30,121 Singh, K. B., Gajri, P. R. and Arora, V. K. (2002). Modelling the effects of soil and water management practices on the water balance and performance of rice. Agricultural Water Management, 49: 77–95. Singh, S. P. and Pillai, K. G. (1994). Response to nitrogen in semidwarf scented rice varieties. International Rice Research Newsletter 19(4): 17. Singh, M. K., Thakur, R., Verma, U. N., Uposari, R. R. and Pul, S. K. (2000). Effect of planting time and nitrogen on production potential of Basmati rice (Oryza sativa) cultivars in Bihor Ploteau. Indian Journal of Agronomy. 49(2): 303-305. Singh P, Agrawal M, Agrawal B. (2009). Evaluation of physiological, growth and yield responses of a tropical oil crop (Brassica campestris L. var. Kranti) under ambient ozone pollution at varying NPK levels. Environmental Pollution 157: 871-880. Smith, M. (2000). The application of climatic data for planning and management ofsustainable rainfed and irrigated crop production. Agricultural and Forest Meteorology, 103: 99–108. Snyder, C.S. and Slaton, N.A. (2002). Rice production in the United States-An Overview. Better crops 16:30-35. 94 University of Ghana http://ugspace.ug.edu.gh Song, C. Y., Zhang, X. Y., Liu, X. B., Sui, Y. Y., & Li, Z. L. (2010). Impact of long term fertilization on soil water content in Haploborolls. Plant Soil Environment, 56,2010(9): 408– 411. Steponkus, P. L., Culture J. C. and Toole J. C. O. (1980). Adaptation to water deficit in rice. In: N. C. Turner and Kramer (eds.) Adaptation of plants to water and temperature stress. Wiley Interscience, New York, USA. pp. 401-418. Subramanian, D. (2008). Water Deficit Condition Affecting Rice Production – Challenges and Prospects. Crop Production Technologies, 6: 1–24. Suriadi Ahmad (2010). Field evaluation and modelling of water and nitrogen management strategies in tropical lowland rice–based production systems. PhD thesis. University Of Southern Queensland, Australia. Tabbal, D. F., Lampayan, R. M. and Bhuiyan, S.I. (1992). Water-efficient irrigation techniques for rice. In: Murty, V. V. N. and Koga, K (Eds.). Soil and water engineering for paddy field management. pp. 146-159. Proceedings of the International Workshop on Soil and Water Engineering for Paddy Field Management, 28-30 January 1992, Asian Institute of Technology, Bangkok,Thailand. Tabbal, D. F., Bouman, B. A. M., Bhuiyan, S. I., Sibayan, E. B., Sattar, M. A. (2002). On-farm strategies for reducing water input in irrigated rice; case studies in the Philippines. Agricultural Water Management, 56: 93– 112. Tajima, K. (1995) Occurrence and mechanism of drought damage. In : T. Matuso, K. Kumazawa, R. Ishii, K. Isihara and H. Hitara (eds.) Science of the rice plant. Physiology. Food and Agriculture Policy Research Center, Tokyo, Japan. pp. 838-849. Talpur M. A., Changying, J Junejo, S. A.,Tagar A. A. and Ram B. K. (2013). Effect of different water depths on growth and yield of rice. African Journal of Agricultural Research. 8(37), 4654-4659 Tan, X., Shao, D., Liu, H., Yang, F., Xiao, C. and Yang, H. (2013). Effects of alternatte wetting and drying irrigation on percolation and nitrogen leaching in paddy fields. Paddy Watter Environment. 11, 1-15 Tayefe, M., Gerayzade, A., and Zade, A. N. (2011). Effect of nitrogen fertilizer on nitrogen uptake , nitrogen use efficiency of rice. International Conference on Biology, Environment and Chemistry 24: 470–473. Thakur, R. B., (1993). Performance of summer rice (Oryza sativa) to varying levels of nitrogen. Indian Journal of Agronomy, 38(2): 187-190. Timsina, J. and Connor, D. J. (2001). Productivity and management of rice-wheat systems: issue 95 University of Ghana http://ugspace.ug.edu.gh and Challenges. Field Crop Research, 69: 93-132. Tomlins, K., Manful, J., Larweh, P. and Hammond, L. (2005). Urban consumer preference and sensory evaluation of locally produced and imported ice in West Africa. Food Quality and Preference, 16: 79-89. Troare, K. (2005). Characterization of Novel Rice Germplasm from West Africa and Genetic Marker Association with Rice Cooking Quality. PhD thesis. Texas A and M University. Texas, USA Tuong, T. P. (2003). Rice Production in Water-scarce Environments. In Water productivity in agriculture: limit and opportunities forimprovement (eds. JW Kijne, R Barker and D Molden) 53–67. Tuong, T. P. and Bouman, B. A. M. (2003). Rice production in water scarce environment. In Water productivity in agriculture: limit and opportunities forimprovement (eds. JW Kijne, R Barker and D Molden), pp 53-67. CABI Publishing, Wallingford, UK Tuong, T. P., Bouman, B. A.M. and Mortimer, M. (2005). More rice, less waterintegrated approaches for increasing water productivity in irrigated rice-based systems in Asia. Plant Production Science. 8: 231-241. UNEP (2008). Vital Water Graphics – An overview of the state of the world’s fresh and marine waters, 2nd edn. United Nations Environment Programme, Nairobi, Kenya. Verma AK., Pandey N and Tripathy RS (2004). Leaf growth, chlorophyll, nitrogen content and grain yield of hybrid rice as influenced by planting times and N levels. Annals of Agriculture Research New Series. 24(3):456-458 Vries, M. E., Rodenburg, J., Bado, B. V., Sow, A., Leffelaar, P. A., and Giller, K. E. (2010). Rice production with less irrigation water is possible in a Sahelian environment. Field Crops Research, 116(1-2): 154–164. Visperas, R. M., Bouman, B. A. M., Peng, S., and Castan, A. R. (2005). Yield and water use of irrigated tropical aerobic rice systems, International Rice Research Institute. 74: 87–105. WARDA. (1993). West Africa Rice Development Association Annual Report 1992. Mbé, Côte d’Ivoire WARDA. (2004). West Africa Rice Development Association Annual Report 2004. Mbé, Côte d’Ivoire Wardana, I. P.; A. Gania; S. Abdulrachman; P.S. Bindraban and H. Van Keulenb. (2010). Enhancing water and fertilizer saving without compromising rice yield through integrated crop management. Indonesian Journal of Agriculture Science 11(2):65-73. 96 University of Ghana http://ugspace.ug.edu.gh Wassmann, R., Jagadish, S. V. K., Heuer, S., Ismail, A., Redona, E., Serraj, R.,Sumfleth, K. (2009). Chapter 2 Climate Change Affecting Rice Production (Vol. 101). Webb B.D (1991). Rice quality and grade. In B. S. Luh, ed. Rice utilization, pp. 89-119. New York, Van Nostrand Reinhold. Weerakoon, W. M. W., Priyadarshani, T. N. N., Piyasiri, C. H., and Silva, L. S. (2010). Impact of Water Saving Irrigation Systems on Water Use , Growth and Yield of Irrigated Lowland Rice. IWMI Conference, 57–64. Witt, C., Buresh, R., Balasubramanian, V., Dawe, D., and Dobermann, (2002). Improving Nutrient Management Strategies for Delivery in Irrigated Rice in Asia. Better Crops International, 16: 24–31. Ximing, C., and Rodegrant, M.W. (2003). World water productivity, Current Situation and Future Options. In: Kijne.J.W., R.Barker and D.Molden (Eds), Water Productivity in Agriculture: Limits and Opportunities for Improvement. CABI Publishing. UK. Pp -163- 178. Yang, X., Bouman, B.A.M.,Wang, H.,Wang, Z., Zhao, J., Chen, B., (2005). Performance of temperate aerobic rice under different water regimes in North China. Agriculture Water Management. 74:107–122. Ye, Y., Liang, X., Chen, Y., Liu, J., Gu, J., Guo, R., and Li, L. (2013). Alternate wetting and drying irrigation and controlled-release nitrogen fertilizer in late-season rice . Effects on dry matter accumulation , yield , water and nitrogen use. Field Crops Research, 144: 212–224. Yoshida, S. (1981). Fundamentals of Rice Crop Science, IRRI, Philippines, PP.1-41. Zare, N., Khaledian, M., Pirmoradian, N., & Rezaei, M. (2014). Simulation of rice yield under different irrigation and nitrogen application managements by Crop System model. Acta Agriculturae Slovenica, 103(2): 181–190. Zhang, H., Xue, Y., Wang, Z., Yang, J., & Zhang, J. (2009). An alternate wetting and moderate soil drying regime improves root and shoot growth in rice. Crop Science, 49(6): 2246–2260. Zubaer, M. A., Chowdhury, A. K., Islam, M. Z., Hasan, M. A., and AHMED, T. (2007). Effects of Water Stress on Growth and Yield Attributes of Aman Rice Genotypes. International Journal of Sustainable Crop Production, 2(6): 25–30. 97 University of Ghana http://ugspace.ug.edu.gh APPENDICES Appendix A: ANOVA for parameters in pot experiment Appendix A1: ANOVA for plant height at active tillering d.f. s.s. m.s. v.r. F pr. Rep stratum 3 17.634 5.878 2.82 Water 2 8.602 4.301 2.06 0.149 N fertilizer 2 80.351 40.175 19.27 <.001 Water. N fertilizer 4 8.654 2.164 1.04 0.408 Residual 24 50.028 2.085 Total 35 165.27 Appendix A2: ANOVA for plant height at maximum tillering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 3.266 1.089 0.39 Water 2 12.934 6.467 2.33 0.119 N fertilizer 2 68.151 34.075 12.25 <.001 Water.N ferttilizer 4 2.634 0.659 0.24 0.915 Residual 24 66.734 2.781 Total 35 153.719 Appendix A3: ANOVA for plant height at booting Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 1.7719 0.5906 1.22 Water 2 2209.785 1104.893 2273.14 <.001 N fertilizer 2 1369.732 684.8658 1409 <.001 Water.N_Levels 4 94.1533 23.5383 48.43 <.001 Residual 24 11.6656 0.4861 Total 35 3687.108 98 University of Ghana http://ugspace.ug.edu.gh Appendix A4: ANOVA for plant height at Harvest(cm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.1756 0.0878 0.1 Water 2 428.207 214.103 238.92 <.001 N fertilizer 2 1839.08 919.541 1026.15 <.001 Water. N fertilizer 4 45.8444 11.4611 12.79 <.001 Residual 16 14.3378 0.8961 Total 26 2327.65 Appendix A5: ANOVA for tiller numbers at active tillering stage Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 2.75 0.9167 2.59 Water 2 2.3889 1.1944 3.37 0.051 N fertilizer 2 12.0556 6.0278 17.02 <.001 Water. N fertilizer 4 1.2778 0.3194 0.9 0.478 Residual 24 8.5 0.3542 Total 35 26.9722 Appendix A6: ANOVA for tiller numbers at maximum tillering stage Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 6.9722 2.3241 5.43 Water 2 56.1667 28.0833 65.58 <.001 N fertilizer 2 340.6667 170.3333 397.75 <.001 Water. N fertilizer 4 12.6667 3.1667 7.39 <.001 Residual 24 10.2778 0.4282 Total 35 426.75 99 University of Ghana http://ugspace.ug.edu.gh Appendix A7: ANOVA for tiller numbers at booting stage Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 10.3333 3.4444 3.65 Water 2 78.5 39.25 41.56 <.001 N fertilizer 2 318.5 159.25 168.62 <.001 Water.N fertilizer 4 13 3.25 3.44 0.023 Residual 24 22.6667 0.9444 Total 35 443 Appendix A8: ANOVA for tiller numbers at harvest Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3.6296 1.8148 2.12 Water 2 109.8519 54.9259 64.13 <.001 N fertilizer 2 176.0741 88.037 102.79 <.001 Water.N fertilizer 4 10.3704 2.5926 3.03 0.049 Residual 16 13.7037 0.8565 Total 26 313.6296 Appendix A9: ANOVA for aboveground biomass at mid- tillering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 1 0.3472 0.3472 3.06 Water 2 6.0844 3.0422 26.81 <.001 N fertilizer 2 4.2544 2.1272 18.75 <.001 Water. N fertilizer 4 0.2022 0.0506 0.45 0.773 Residual 8 0.9078 0.1135 Total 17 11.7961 100 University of Ghana http://ugspace.ug.edu.gh Appendix A10: ANOVA for aboveground biomass accumulation at booting Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 1 1.0272 1.0272 2.58 Water 2 938.2878 469.1439 1177.36 <.001 N fertilizer 2 2681.121 1340.561 3364.25 <.001 Water. N fertilizer 4 110.6056 27.6514 69.39 <.001 Residual 8 3.1878 0.3985 Total 17 3734.229 Appendix A11: ANOVA for aboveground biomass accumulation at harvest Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 1.9607 0.9804 1.65 Water 2 1675.22 837.612 1411.81 <.001 N fertilizer 2 2954.32 1477.16 2489.79 <.001 Water. N fertilizer 4 196.193 49.0481 82.67 <.001 Residual 16 9.4926 0.5933 Total 26 4837.19 Appendix A12: ANOVA for leaf area index at booting Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 0.02 0.00667 0.19 Water 2 11.3372 5.66861 158.19 <.001 N fertilizer 2 40.9306 20.4653 571.12 <.001 Water. N fertilizer 4 0.42111 0.10528 2.94 0.041 Residual 24 0.86 0.03583 Total 35 53.5689 101 University of Ghana http://ugspace.ug.edu.gh Appendix A13: ANOVA for leaf chlorophyll content at flowering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 5.123 2.5615 2.87 Water 2 151.95 75.9748 85.06 <.001 N fertilizer 2 1460.67 730.336 817.71 <.001 Water. N fertilizer 4 78.2837 19.5709 21.91 <.001 Residual 16 14.2904 0.8931 Total 26 1710.32 Appendix A14: ANOVA for days to 50 % flowering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 2.7407 1.3704 3.33 Water 2 1.4074 0.7037 1.71 0.213 N fertilizer 2 1.1852 0.5926 1.44 0.266 Water. N fertilizer 4 1.7037 0.4259 1.03 0.42 Residual 16 6.5926 0.412 Total 26 13.6296 Appendix A15: ANOVA for effective tillers Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3.6296 1.8148 2.12 Water 2 109.8519 54.9259 64.13 <.001 N fertilizer 2 176.0741 88.037 102.79 <.001 Water. N fertilizer 4 10.3704 2.5926 3.03 0.049 Residual 16 13.7037 0.8565 Total 26 313.6296 102 University of Ghana http://ugspace.ug.edu.gh Appendix A16: ANOVA for grains/panicles Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 48.3 24.15 1.4 Water 2 2020.52 1010.26 58.63 <.001 N fertilizer 2 3394.74 1697.37 98.5 <.001 Water. N fertilizer 4 624.81 156.2 9.07 <.001 Residual 16 275.7 17.23 Total 26 6364.07 Appendix A17: ANOVA for percentage filled grains Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.222 0.111 0.06 Water 2 57.556 28.778 16.58 0.083 N fertilizer 2 26 13 7.49 0.005 Water. N fertilizer 4 13.111 3.278 1.89 0.162 Residual 16 27.778 1.736 Total 26 124.667 Appendix A18: ANOVA for Panicle length (cm) Source of variation d.f. s.s. m.s. v.r. F pr. 0.02667 0.01333 0.26 Rep stratum 2 11.50889 5.75444 113.2 <.001 Water 2 47.70889 23.85444 469.27 <.001 N fertilizer 2 2.06889 0.51722 10.17 <.001 Water.N fertilizer 4 0.81333 0.05083 Residual 16 62.12667 Total 26 103 University of Ghana http://ugspace.ug.edu.gh Appendix A19: ANOVA for 1000 grain weight (g) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.0052 0.0026 0 Water 2 1.1852 0.5926 1.08 0.364 N fertilizer 2 0.3585 0.1793 0.33 0.727 Water. N fertilizer 4 1.4815 0.3704 0.67 0.62 Residual 16 8.8081 0.5505 Total 26 11.8385 Appendix A20: ANOVA for grain yield (g/pot) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 1.2067 0.6033 2.23 Water 2 968.46 484.23 1790.68 <.001 N fertilizer 2 3157.91 1578.95 5838.97 <.001 Water. N fertilizer 4 116.124 29.0311 107.36 <.001 Residual 16 4.3267 0.2704 Total 26 4248.03 Appendix A21: ANOVA for straw yield (g/pot) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 1.9607 0.9804 1.65 Water 2 1675.22 837.612 1411.81 <.001 N fertilizer 2 2954.32 1477.16 2489.79 <.001 Water. N fertilizer 4 196.193 49.0481 82.67 <.001 Residual 16 9.4926 0.5933 Total 26 4837.19 104 University of Ghana http://ugspace.ug.edu.gh Appendix A22: ANOVA for harvest index Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.00018 8.94E-05 5.79 Water 2 0.00407 0.00204 131.82 <.001 N fertilizer 2 0.03654 0.01827 1183.5 <.001 Water. N fertilizer 4 0.00157 0.00039 25.4 <.001 Residual 16 0.00025 1.54E-05 Total 26 0.0426 Appendix A22: ANOVA for Nitrogen uptake in grain Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.000114 5.69E-05 3.37 Water 2 0.145217 0.072608 4300.52 <.001 N fertilizer 2 0.679885 0.339943 20134.49 <.001 Water. N fertilizer 4 0.062745 0.015686 929.09 <.001 Residual 16 0.00027 1.69E-05 Total 26 0.888231 Appendix A23: ANOVA for Nitrogen uptake in straw Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.001153 0.000576 21.38 Water 2 0.152116 0.076058 2821.38 <.001 N fertilizer 2 0.815343 0.407671 15122.57 <.001 Water.N fertilizer 4 0.037017 0.009254 343.29 <.001 Residual 16 0.000431 2.7E-05 Total 26 1.00606 105 University of Ghana http://ugspace.ug.edu.gh Appendix A24: ANOVA for agronomic nitrogen use efficiency Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.1111 0.0555 0.06 Water 2 101.1602 50.5801 59.04 <.001 N fertilizer 2 4851.685 2425.843 2831.49 <.001 Water. N fertilizer 4 145.6264 36.4066 42.49 <.001 Residual 16 13.7078 0.8567 Total 26 5112.291 Appendix A25: ANOVA for physiological nitrogen use efficiency Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.771 0.386 0.33 Water 2 234.887 117.443 100.13 <.001 N fertilizer 2 11822.63 5911.316 5039.78 <.001 Water. N fertilizer 4 194.757 48.689 41.51 <.001 Residual 16 18.767 1.173 Total 26 12271.81 Appendix A26: ANOVA for water use (cm3) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.9991 0.4996 0.54 Water 2 3691.184 1845.592 2000.12 <.001 N fertilizer 2 170.5473 85.2736 92.41 <.001 Water. N fertilizer 4 34.6556 8.6639 9.39 <.001 Residual 16 14.7638 0.9227 Total 26 3912.15 Appendix A27: ANOVA for water productivity (g/cm3) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.001324 0.000662 0.7 Water 2 0.275418 0.137709 146.48 <.001 N fertilizer 2 1.137127 0.568564 604.8 <.001 Water. N fertilizer 4 0.077825 0.019456 20.7 <.001 Residual 16 0.015042 0.00094 Total 26 1.506736 106 University of Ghana http://ugspace.ug.edu.gh Appendix B: ANOVA for parameters in field experiment Appendix B1: ANOVA for Plant height at active tillering (cm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 16.062 8.031 4.46 Water 2 22.602 11.301 6.27 0.058 Residual 4 7.209 1.802 0.51 N fertilizer 2 83.536 41.768 11.78 0.001 Water. N fertilizer 4 16.216 4.054 1.14 0.383 Residual 12 42.536 3.545 Total 26 188.16 Appendix B2: ANOVA for lant height at maximum tillering (cm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 8.854 4.427 5.9 Water 2 26.261 13.13 17.51 0.011 Residual 4 2.999 0.75 0.2 N fertilizer 2 40.903 20.451 5.37 0.022 Water. N fertilizer 4 5.017 1.254 0.33 0.853 Residual 12 45.7 3.808 Total 26 129.734 Appendix B3: ANOVA for plant height at booting (cm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 1.6763 0.8381 4.49 Water 2 1999.612 999.8059 5361.42 <.001 Residual 4 0.7459 0.1865 0.94 N fertilizer 2 256.8896 128.4448 650.05 <.001 Water. N fertilizer 4 26.5593 6.6398 33.6 <.001 Residual 12 2.3711 0.1976 Total 26 2287.854 107 University of Ghana http://ugspace.ug.edu.gh Appendix B4: ANOVA for plant height at harvest (cm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3.8422 1.9211 9.27 Rep.Water stratum Water 2 1923.962 961.9811 4642.27 <.001 Residual 4 0.8289 0.2072 0.39 N fertilizer 2 471.8289 235.9144 438.99 <.001 Water. N fertilizer 4 19.1956 4.7989 8.93 0.001 Residual 12 6.4489 0.5374 Total 26 2426.107 Appendix B5: ANOVA for Number of tillers at active tillering stage Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 879.6 439.8 0.93 Water 2 3657.4 1828.7 3.85 0.117 Residual 4 1898.1 474.5 1.64 N fertilizer 2 8101.9 4050.9 14 <.001 Water. N fertilizer 4 509.3 127.3 0.44 0.778 Residual 12 3472.2 289.4 Total 26 18518.5 Appendix B6: ANOVA for number of tillers at maximum tillering stage Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3888.9 1944.4 5.6 Water 2 27222.2 13611.1 39.2 0.002 Residual 4 1388.9 347.2 0.88 N fertilizer 2 160138.9 80069.4 203.47 <.001 Water. N fertilizer 4 6388.9 1597.2 4.06 0.026 Residual 12 4722.2 393.5 Total 26 203750 108 University of Ghana http://ugspace.ug.edu.gh Appendix B7: ANOVA for Number of tillers at booting stage Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 1805.56 902.78 6.5 Water 2 50555.56 25277.78 182 <.001 Residual 4 555.56 138.89 1.71 N fertilizer 2 187222.2 93611.11 1155.43 <.001 Water. N fertilizer 4 5555.56 1388.89 17.14 <.001 Residual 12 972.22 81.02 Total 26 246666.7 Appendix B8: ANOVA for number of tillers at harvest Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 324.1 162 1.27 Water 2 41157.4 20578.7 161.64 <.001 Residual 4 509.3 127.3 1.22 N fertilizer 2 113518.5 56759.3 544.89 <.001 Water. N fertilizer 4 2314.8 578.7 5.56 0.009 Residual 12 1250 104.2 Total 26 159074.1 Appendix B9: ANOVA for Aboveground biomass accumulation at active tillering (g) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3.3785 1.6893 39.66 Water 2 0.323 0.1615 3.79 0.119 Residual 4 0.1704 0.0426 0.07 N fertilizer 2 2.4319 1.2159 1.96 0.184 Water. N fertilizer 4 0.9104 0.2276 0.37 0.828 Residual 12 7.4578 0.6215 Total 26 14.6719 109 University of Ghana http://ugspace.ug.edu.gh Appendix B10: ANOVA for aboveground biomass accumulation at maximum tillering (g) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 85 42 0.01 Water 2 71138 35569 11.98 0.02 Residual 4 11878 2969 2.04 N fertilizer 2 15006 7503 5.15 0.024 Water. N fertilizer 4 10969 2742 1.88 0.178 Residual 12 17479 1457 Total 26 126554 Appendix B11: ANOVA for aboveground biomass accumulation at booting (g) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 11.46 5.73 0.11 Water 2 59658.9 29829.45 561.03 <.001 Residual 4 212.68 53.17 1.98 N fertilizer 2 305369.5 152684.7 5680.08 <.001 Water. N fertilizer 4 781.55 195.39 7.27 0.003 Residual 12 322.57 26.88 Total 26 366356.6 Appendix B12: ANOVA for aboveground biomass accumulation at harvest (g) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 1087.19 543.59 6.15 Water 2 380645.6 190322.8 2152.64 <.001 Residual 4 353.65 88.41 0.91 N fertilizer 2 360429.4 180214.7 1858.85 <.001 Water. N fertilizer 4 18774.52 4693.63 48.41 <.001 Residual 12 1163.39 96.95 Total 26 762453.7 110 University of Ghana http://ugspace.ug.edu.gh Appendix B13: ANOVA for Leaf area index at booting Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.00519 0.00259 0.05 Water 2 8.94296 4.47148 86.86 <.001 Residual 4 0.20593 0.05148 3.16 N fertilizer 2 31.1119 15.5559 954.57 <.001 Water. N fertilizer 4 0.27926 0.06981 4.28 0.022 Residual 12 0.19556 0.0163 Total 26 40.7407 Appendix B14: ANOVA for Leaf area index at flowering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.08667 0.04333 1.05 Water 2 6.64222 3.32111 80.78 <.001 Residual 4 0.16444 0.04111 1.02 N fertilizer 2 32.3356 16.1678 402.33 <.001 Water. N fertilizer 4 0.55556 0.13889 3.46 0.042 Residual 12 0.48222 0.04019 Total 26 40.2667 Appendix B15: ANOVA for Leaf chlorophyll content at flowering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.0563 0.0281 0.55 Water 2 94.2007 47.1004 914.9 <.001 Residual 4 0.2059 0.0515 0.26 N fertilizer 2 334.6319 167.3159 839.69 <.001 Water. N fertilizer 4 2.9837 0.7459 3.74 0.034 Residual 12 2.3911 0.1993 Total 26 434.4696 111 University of Ghana http://ugspace.ug.edu.gh Appendix B16: ANOVA for Days to 50% flowering Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.963 0.4815 0.59 Water 2 5.4074 2.7037 3.32 0.141 Residual 4 3.2593 0.8148 1.52 N fertilizer 2 0.5185 0.2593 0.48 0.629 Water. N fertilizer 4 1.037 0.2593 0.48 0.748 Residual 12 6.4444 0.537 Total 26 17.6296 Appendix B17: ANOVA for panicles/ m2 Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 300.07 150.04 3.83 Water 2 4681.41 2340.7 59.71 0.001 Residual 4 156.81 39.2 0.73 N fertilizer 2 104006.7 52003.37 965.34 <.001 Water. N fertilizer 4 2229.48 557.37 10.35 <.001 Residual 12 646.44 53.87 Total 26 112021 Appendix B18: ANOVA for grains/panicles Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 8.074 4.037 10.9 Water 2 5183.63 2591.815 6997.9 <.001 Residual 4 1.481 0.37 0.07 N fertilizer 2 3450.296 1725.148 321.23 <.001 Water. N fertilizer 4 513.259 128.315 23.89 <.001 Residual 12 64.444 5.37 Total 26 9221.185 112 University of Ghana http://ugspace.ug.edu.gh Appendix B19: ANOVA for panicle length (cm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.1919 0.0959 0.71 Water 2 8.7696 4.3848 32.26 0.003 Residual 4 0.5437 0.1359 1.04 N fertilizer 2 46.743 23.3715 178.51 <.001 Water. N fertilizer 4 2.2059 0.5515 4.21 0.023 Residual 12 1.5711 0.1309 Total 26 60.0252 Appendix B20: ANOVA for percentage filled grains Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 9.185 4.593 1.94 Water 2 50.074 25.037 10.56 0.25 Residual 4 9.481 2.37 2.13 N fertilizer 2 31.63 15.815 14.23 <.001 Water. N fertilizer 4 40.37 10.093 9.08 0.001 Residual 12 13.333 1.111 Total 26 154.074 Appendix B21: ANOVA for 1000 grain weight (g) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.2452 0.1226 0.37 Water 2 1.7163 0.8581 2.56 0.192 Residual 4 1.3415 0.3354 0.88 N fertilizer 2 0.0741 0.037 0.1 0.908 Water. N fertilizer 4 1.2793 0.3198 0.84 0.527 Residual 12 4.58 0.3817 Total 26 9.2363 113 University of Ghana http://ugspace.ug.edu.gh Appendix B22: ANOVA for grain yield (t/ha) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 0.03185 0.01593 0.47 Water 2 10.57852 5.28926 156.93 <.001 Residual 4 0.13481 0.0337 0.78 N fertilizer 2 42.01407 21.00704 484.78 <.001 Water. N fertilizer 4 1.58593 0.39648 9.15 0.001 Residual 12 0.52 0.04333 Total 26 54.86519 Appendix B23: Harvest index Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 5.97E-05 2.98E-05 0.16 Water 2 0.000571 0.000286 1.5 0.327 Residual 4 0.000762 0.000191 1.33 N fertilizer 2 0.000366 0.000183 1.27 0.315 Water. N fertilizer 4 0.00422 0.001055 7.35 0.003 Residual 12 0.001722 0.000144 Total 26 0.0077 Appendix B24: ANOVA for Nitrogen uptake in grain Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 6.546 3.273 0.65 Water 2 2586.338 1293.169 258.08 <.001 Residual 4 20.043 5.011 0.96 N fertilizer 2 15169.55 7584.776 1448.93 <.001 Water. N fertilizer 4 1605.769 401.442 76.69 <.001 Residual 12 62.817 5.235 Total 26 19451.07 114 University of Ghana http://ugspace.ug.edu.gh Appendix B25: ANOVA for nitrogen uptake in straw Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 9.855 4.9275 14.18 Water 2 986.8198 493.4099 1419.91 <.001 Residual 4 1.39 0.3475 0.7 N fertilizer 2 8060.181 4030.091 8090.87 <.001 Water. N fertilizer 4 455.6105 113.9026 228.67 <.001 Residual 12 5.9772 0.4981 Total 26 9519.834 Appendix B26: ANOVA for agronomic nitrogen use efficiency Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 6.127 3.064 0.41 Water 2 303.589 151.795 20.18 0.008 Residual 4 30.087 7.522 0.93 N fertilizer 2 5628.624 2814.312 347.73 <.001 Water. N fertilizer 4 196.068 49.017 6.06 0.007 Residual 12 97.119 8.093 Total 26 6261.614 Appendix B27: ANOVA for Physiological nitrogen use efficiency Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 30.33 15.17 0.89 Water 2 49.99 25 1.47 0.332 Residual 4 68.08 17.02 1.41 N fertilizer 2 10483.14 5241.57 435.29 <.001 Water. N fertilizer 4 157.49 39.37 3.27 0.05 Residual 12 144.5 12.04 Total 26 10933.53 115 University of Ghana http://ugspace.ug.edu.gh Appendix B28: ANOVA for water use (mm) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3.25E+01 1.63E+01 6.14 Water 2 4.38E+06 2.19E+06 8.26E+05 <.001 Residual 4 1.06E+01 2.65E+00 0.51 N fertilizer 2 3.80E+04 1.90E+04 3627.23 <.001 Water. N fertilizer 4 2.39E+03 5.97E+02 113.96 <.001 Residual 12 6.29E+01 5.24E+00 Total 26 4.42E+06 Appendix B29: ANOVA for water productivity (cm3) Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 2 3.57E-05 1.78E-05 0.07 Water 2 0.353933 0.176966 683.46 <.001 Residual 4 0.001036 0.000259 0.55 N fertilizer 2 0.319308 0.159654 338.07 <.001 Water. N fertilizer 4 0.010041 0.00251 5.32 0.011 Residual 12 0.005667 0.000472 Total 26 0.69002 116 University of Ghana http://ugspace.ug.edu.gh Appendix C: Economics analysis for rice production Appendix C1: General cost of rice production (GH₵/ha) under different water management and Nitrogen treatment combinations during July to November 2015 at Soil and Irrigation Research Centre, Kpong General cost of production Amount (GH₵/ha) Land preparation 150 Bund making and digging 100 Cost of herbicide 30 Labour for application of herbicide 20 Cost of pesticide 30 Labour for application of pesticide 20 cost of muriate of potash (K20) 157.5 cost of triple Superphosphate (P2O5) 205.4 Cost of seeds 220 Cost of transplanting of seedlings 200 Labour for scaring of birds 300 Harvesting and threshing 900 Total cost 2333 117 University of Ghana http://ugspace.ug.edu.gh Appendix C2. Variable cost of rice production (GH₵/ha) under different water management and Nitrogen treatment combinations during July to November 2015 at Soil and Irrigation Research Centre, Kpong Treatment Expenditure Total (GH₵/ha) AWDN0 General cost of cultivation 2333 cost of water 1200 Total 3533 AWDN1 General cost of cultivation 2333 cost of water 1200 cost of Urea 273 Total 3806 AWDN2 General cost of cultivation 2333 cost of water 1200 cost of Urea 409.5 Total 3942.5 MCN0 General cost of cultivation 2333 Cost of water 600 Total 2933 MCN1 General cost of cultivation 2333 Cost of water 600 Cost of Urea 273 Total 3206 MCN2 General cost of cultivation 2333 Cost of water 600 Cost of Urea 409.5 118 University of Ghana http://ugspace.ug.edu.gh Total 3342.5 CSN0 General cost of cultivation 2333 Cost of water 1600 Total 3933 CSN1 General cost of cultivation 2333 cost of water 1600 cost of Urea 273 Total 4206 CSN2 General cost of cultivation 2333 cost of water 1600 cost of Urea 409.5 Total 4342.5 119