University of Ghana http://ugspace.ug.edu.gh BIOCHAR AS A LIMING AGENT AND PHOSPHORUS SOURCE TO ENHANCE THE GROWTH OF SOYA BEAN IN TWO ACID SOILS. BY ELVIS FRIMPONG MANSO (10339188) A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE AWARD OF DEGREE OF MASTER OF PHILOSOPHY IN SOIL SCIENCE DEPARTMENT OF SOIL SCIENCE, SCHOOL OF AGRICULTURE, COLLEGE OF BASIC AND APPLIED SCIENCES UNIVERSITY OF GHANA, LEGON JULY, 2017 University of Ghana http://ugspace.ug.edu.gh DECLARATION I hereby declare that this thesis has not been submitted for a degree to any other university and it is entirely my own work and all help and references have been duly acknowledged. …………....………………………………………………… ELVIS FRIMPONG MANSO (STUDENT) .................……………………………………………………….. Dr. E. K. NARTEY (PRINCIPAL SUPERVISOR) ………………………………………………………………… Dr. T. A. ADJADEH (SUPERVISOR) i University of Ghana http://ugspace.ug.edu.gh DEDICATION This thesis is dedicated to omnipotent God for his grace and mercy and family, especially my caring and supporting great grandmother Nana Twenewaah Konadu, Mrs. Augustina Adusei, Mr. Stephen Adusei and Mrs. Margaret Mensah who in numerous ways have stood beside me and kept me in their thoughts and prayers. ii University of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGEMENT I wish to express my sincere gratitude to my supervisors, Dr. E. K. Nartey and Dr. T. A. Adjadeh of the Department of Soil Science, School of Agriculture, University of Ghana for their kind advice, guidance, support and constructive criticisms during my entire study. My profound gratitude goes to The USAID-Ghana/University of Ghana Institutional Capacity Building for Agricultural Productivity Project for funding this study and not forgetting Prof. John Ofosu-Anim, Dean, School of Agriculture, University of Ghana through which this fund was secured. Many thanks to Mr. Ezekiel Odonkor, Project Coordinator for his support and care throughout my study. My acknowledgement would not be complete without mentioning the immense contribution from all lecturers of the Department of Soil Science especially, Dr. I. Y. D. Lawson, the head of department, Prof M. K. Abekoe, Prof. E. Owusu-Bennoah and Dr. Mrs. S. A. Brempong. To all technicians and service personnel of Department of Soil Science especially Mr. V. A. Okrah for his support and fatherly advice throughout my time in the department, Mr. E. Annum, Mr. Christian of Ecological laboratory, Mr. A. A. Francis, Mr. S. Nasirudeen, Mr. A. Henry and Mr. N. John, I say God bless you. Finally, many thanks to my course mates and colleague students especially Mr. D. Ansah Fianko, Mr. D. Richard, Ms. A. Asamoah-Bediako, Mr. K. M. Asiwome, Ms. T. Abigail and Mr. E. O. Joseph. I pray God see you through in all your day to day endeavours. iii University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENT DECLARATION ............................................................................................................................. i DEDICATION ................................................................................................................................ ii ACKNOWLEDGEMENT ............................................................................................................. iii TABLE OF CONTENT ................................................................................................................. iv LIST OF TABLES ......................................................................................................................... xi LIST OF FIGURES ..................................................................................................................... xiii LIST OF PLATES ........................................................................................................................ xv ABSTRACT ................................................................................................................................. xvi CHAPTER ONE ........................................................................................................................... 1 1 INTRODUCTION................................................................................................................. 1 Background ................................................................................................................... 1 Problem Statement........................................................................................................ 6 Justification ................................................................................................................... 6 Objectives....................................................................................................................... 9 Hypothesis ...................................................................................................................... 9 CHAPTER TWO .......................................................................................................................... 10 2 LITERATURE REVIEW ..................................................................................................... 10 Definition of pH ............................................................................................................ 10 iv University of Ghana http://ugspace.ug.edu.gh Causes of Soil Acidity .............................................................................................. 10 Types of Soil Acidity ................................................................................................ 13 Active Acidity ............................................................................................................... 13 Exchangeable Acidity ................................................................................................... 13 Residual Acidity............................................................................................................ 14 Effect of Soil Acidity on Nutrient Availability and Plant Growth ........................... 14 Control of Soil Acidity.............................................................................................. 16 Lime Requirement ........................................................................................................ 18 Types of Liming Materials........................................................................................ 19 Advantages of Liming in Acidic Soils ...................................................................... 19 Biochar .......................................................................................................................... 21 Biochar Production ................................................................................................... 21 Biochar Stability in the Soil ...................................................................................... 22 Structural Composition of Biochar ........................................................................... 23 Chemical Composition of Biochar and Surface Chemistry ...................................... 23 Functional Groups ......................................................................................................... 25 Biochar as Liming Material ...................................................................................... 26 Mode of Biochar Application ....................................................................................... 27 Topsoil Application .................................................................................................. 27 v University of Ghana http://ugspace.ug.edu.gh Depth Application ..................................................................................................... 28 Top Dressing ............................................................................................................. 28 Agronomic Importance of Biochar ............................................................................... 29 Importance of Biochar in the Environment .................................................................. 31 Sequestration of Carbon ............................................................................................ 31 Impact on Soil Performance and Resource Implications .......................................... 31 Biochar and Nitrogen Fertilizer Interactions ............................................................ 33 Negative Effect of Biochar Applied to the Soil ........................................................ 33 Origin and History of Soya bean .................................................................................. 34 Importance of Soya bean .......................................................................................... 35 Factors that Affect Growth and Yield of Soya bean ..................................................... 36 Nodulation................................................................................................................. 37 Soil Temperature ........................................................................................................... 38 Soil pH Stress ................................................................................................................ 38 Soil Water Availability ................................................................................................. 39 Availability of Phosphorus ........................................................................................... 39 Population of Rhizobia Strain in the Soil ..................................................................... 40 Soil Nutrient .................................................................................................................. 41 CHAPTER THREE ...................................................................................................................... 42 vi University of Ghana http://ugspace.ug.edu.gh 3 MATERIALS AND METHODS .......................................................................................... 42 Soils and Sampling ....................................................................................................... 42 Soil Characterisation ..................................................................................................... 42 Total Phosphorus ...................................................................................................... 43 Physical Properties .................................................................................................... 43 Bulk Density (Core Method) ........................................................................................ 43 Particle Size Analysis ................................................................................................... 45 Moisture Content at Field Capacity .............................................................................. 46 Soil Chemical Properties........................................................................................... 47 Soil pH .......................................................................................................................... 47 Total Carbon and Nitrogen ........................................................................................... 47 Available Nitrogen ........................................................................................................ 47 Available Phosphorus ................................................................................................... 49 Total Phosphorus .......................................................................................................... 50 Exchangeable Bases and Cation Exchange Capacity (CEC) ........................................ 50 Extraction of Exchangeable Bases. ............................................................. 50 Cation Exchange Capacity (CEC) ............................................................... 51 Exchangeable Acidity (H+ and Al3+). ........................................................................... 51 Effective Cation Exchange Capacity (ECEC) .............................................................. 52 vii University of Ghana http://ugspace.ug.edu.gh Preparation of Biochar .................................................................................................. 52 Biochar pH ................................................................................................................ 53 Biochar Available Phosphorus .................................................................................. 53 Exchangeable Cations in Biochar ............................................................................. 54 Soluble Cations in Biochar ........................................................................................... 54 Incubation Study ........................................................................................................... 54 Evaluation of Effect of Liming on Growth Characteristics of Soya bean .................... 55 Crop Parameters Determined .................................................................................... 59 Total P of Plant Material ............................................................................................... 59 Residual Analyses ..................................................................................................... 60 Soil Residual pH ........................................................................................................... 60 Soil Residual Available Phosphorus ............................................................................. 60 Soil Residual Total Nitrogen and Carbon ..................................................................... 61 Data Analyses ............................................................................................................... 61 CHAPTER FOUR ......................................................................................................................... 62 4 RESULTS ............................................................................................................................. 62 Characterization of Soils. .............................................................................................. 62 Chemical Characterisation of Biochar .......................................................................... 64 Effect of Amendments on Soil pH ................................................................................ 68 viii University of Ghana http://ugspace.ug.edu.gh Effect of Amendments on Changes in Concentration of Exchangeable Al and Ca in the Soil 70 Effects of Amendment on Mg2+, K+, Na+ and H+ Concentrations in the Soil. ............. 72 Changes in Available P with Liming ............................................................................ 75 Effect of Liming Amendments on Growth Parameters of Soya bean .......................... 76 Effect of Liming on Root Volume ............................................................................ 82 Effect Liming on Root Dry Matter ........................................................................... 86 Effect of Liming on Shoot Dry Matter ..................................................................... 86 Effect of P on Growth Parameters of Soya bean .......................................................... 89 Effect of P on Root Volume...................................................................................... 89 Effect of P on Root Dry Matter................................................................................. 91 Effect of P on Shoot Dry Matter ............................................................................... 91 Effect of P on Nodulation ......................................................................................... 94 Effect of N Application on Growth Characteristics of Soya Bean ............................... 94 Effect of N on Shoot Dry Matter .............................................................................. 94 Effect of N on root volume and Nodule Number ..................................................... 97 Interactive Effects of Biochar Liming, Synthetic P and N Application on Growth Characteristics ........................................................................................................................... 97 Nutrient Uptake ........................................................................................................... 102 Root P Uptake ................................................................................................. 102 ix University of Ghana http://ugspace.ug.edu.gh Shoot P Uptake ............................................................................................... 105 CHAPTER FIVE ........................................................................................................................ 114 5 DISCUSSION ..................................................................................................................... 114 Soil Characterization ................................................................................................... 114 Biochar Characterization ............................................................................................ 116 Effect of Liming on pH and Availability of Bases. .................................................... 118 Effect of Liming on P Availability ............................................................................. 124 5.5. Effect of Soil Amendments on Plant Growth Parameter ................................................. 126 5.6. Liming and P Availability on Nodulation ........................................................................ 130 5.7. Residual Nutrients ............................................................................................................ 131 CHAPTER SIX ........................................................................................................................... 134 6 CONCLUSIONS AND RECOMMENDATION ............................................................... 134 Conclusions ................................................................................................................. 134 Recommendation ........................................................................................................ 135 REFERENCE .............................................................................................................................. 136 APPENDICES ............................................................................................................................ 171 x University of Ghana http://ugspace.ug.edu.gh LIST OF TABLES Tables Page Table 2. 1: Descriptive Terms Associated with Soil pH ............................................................... 11 Table 4. 1: Some Physical and Chemical Properties of the Soils Used ........................................ 63 Table 4. 2: Chemical Properties of Feedstock and Biochar Types Used* .................................... 65 Table 4. 3: Total, Exchangeable and Soluble Bases of Feedstock and Biochar Types Used* ..... 66 Table 4. 4: Response of Root Volume to Different Liming Material* ......................................... 85 Table 4. 5: Response of Root Dry Matter to Different Liming Materials* .................................. 87 Table 4. 6: Response of Shoot Dry Matter to Different Liming Materials* ................................. 88 Table 4. 7: Effect of P on Root Volume* ..................................................................................... 90 Table 4. 8: Response of Root Dry Matter to Different P Source* ................................................ 92 Table 4. 9: Response of Shoot Dry Matter to Synthetic and Biochar P Sources* ........................ 93 Table 4. 10: Effect of P on Nodule Number and Nodule Matter* ................................................ 95 Table 4. 11: Interactive Effects of Amendment on Root Volume, Shoot Dry Matter and Nodule Number in Ankasa Series*............................................................................................................ 99 xi University of Ghana http://ugspace.ug.edu.gh Table 4. 12: Interactive Effect of Amendment on Root Volume, Shoot Dry Matter and Nodule Number in Tikobo Series* .......................................................................................................... 101 Table 4. 13: Effect of Amendments on Root P Uptake* ............................................................ 103 Table 4. 14: Effect of Amendments on Shoot P Uptake* ........................................................... 106 Table 4. 15: Effect of Amendments on TC, TN, TP and AP in Ankasa Series* ........................ 108 Table 4. 16: Effect of Amendments on C, N, TP and AP in Tikobo Series* ............................. 110 Table 4. 17: Effect of Amendment on Residual Al and pH* ...................................................... 112 Table 5. 1: Shoot to Root Dry Weight Ratio on Ankasa and Tikobo Series*. ........................... 129 Table 5. 2: Apparent Phosphorus Recovery Efficiency in Ankasa and Tikobo Series* ............. 132 xii University of Ghana http://ugspace.ug.edu.gh LIST OF FIGURES Figure 1. Changes in pH upon addition of amendments in Ankasa Series ................................... 69 Figure 2. Changes in pH upon addition of amendments in Tikobo Series ................................... 69 Figure 3. Changes in Al and Ca concentration upon addition of amendments to Ankasa Series. 71 Figure 4. Changes in Al and Ca concentration upon addition of amendments to Tikobo Series. 73 Figure 5. Changes in Mg concentration upon addition of amendments to Ankasa Series ........... 73 Figure 6. Changes in Mg concentration upon addition of amendments to Tikobo Series ............ 74 Figure 7. Changes in K concentration upon addition of amendments to Ankasa Series .............. 77 Figure 8. Changes in K concentration upon addition of amendments to Tikobo Series .............. 77 Figure 9. Changes in Na concentration upon addition of amendments to Ankasa Series ............ 78 Figure 10. Changes in Na concentration upon addition of amendments to Tikobo Series ........... 78 Figure 11 Changes in H concentration upon addition of amendments to Ankasa Series ............. 79 Figure 12. Changes in H concentration upon addition of amendments to Tikobo Series ............ 79 Figure 13. Changes in P concentration after addition of amendments to Ankasa Series ............. 80 Figure 14. Changes in P concentration after addition of amendments to Tikobo Series .............. 81 Figure 15. Response of shoot dry mass to N application .............................................................. 96 xiii University of Ghana http://ugspace.ug.edu.gh Figure 16. Response of root volume to N application .................................................................. 98 Figure 17. Response of nodulation to N application..................................................................... 98 Figure 18. Relationship between exchangeable Ca and exchangeable Al. ................................. 120 Figure 19. Relationship between sum of bases (Mg, K, Na) and exchangeable Al. ................... 120 Figure 20 Relationship between sum of bases (Mg, K, Na) and pH. ......................................... 121 Figure:21a: Relationship between Exchangeable Al and Mg ..................................................... 121 Figure 21b: Relationship between pH and Mg ........................................................................... 121 Figure 22a: Relationship between exchangeable Al and Mg...................................................... 122 Figure 22b: Relationship between pH and Mg ........................................................................... 122 Figure 23 Relationship Between Available P and Al ................................................................. 125 xiv University of Ghana http://ugspace.ug.edu.gh LIST OF PLATES Plate 1 Experimental set up of the incubation study in the screen house ..................................... 56 Plate 2 Pot experiment showing soya bean plants in the screen house. ........................................ 58 Plate 3. Soya bean Root in Ankasa Series .................................................................................... 83 Plate 4. Soya bean Root in Tikobo Series ..................................................................................... 84 xv University of Ghana http://ugspace.ug.edu.gh ABSTRACT Unavailability and high cost of conventional liming materials have contributed largely to low food production in acid soils of Ghana. Biochar produced from agricultural waste materials have high concentration of basic cations and available P that could be exploited for use as liming material and/or P source. However, the biochar type that will provide a conducive soil pH vis-à-vis P availability for food crop production in acid soils of Ghana has received little attention. Consequently, two typical acid soils, Ankasa series (Plinthic Acrudox) and Tikobo series (Typic Hapludult) were amended with corn cob and rice husk biochar types charred at 500 and 700 oC at a rate of 80 tons/ha in a screen house experiment to ascertain the efficacy of the biochar types as substitutes for agricultural lime and sources of P. The Ca equivalent of the biochar types from CaCO3 was amended to the soils to serve as a realistic control. The amended soils in addition to their un-amended counterparts were all kept at 80% field capacity in a completely randomized design in the screen house to allow for pH equilibration amidst weekly pH and bi-weekly exchangeable Al and basic cations monitoring. After pH equilibration, inoculated soya bean seeds were sown at stake. Nitrogen was applied at rates of 0 kg/ha and 10 kg/ha. Phosphorus was applied at zero and the biochar P equivalent from triple super phosphate was applied to the non- biochar-amended soils. Extra 30 kg P/ha from TSP was applied to some of the biochar amended soils to ascertain if any, the combined effect of synthetic P and biochar on growth and nodulation of soya bean. At flower initiation, crops were harvested, nodules counted, root volume, shoot and root dry matter and P uptake were determined. Results showed that corn cob charred at 700 oC was able to raise pH from 4.2 to 5.2 in Ankasa Series and from 4.9 to 6.2 in Tikobo Series within a six- week incubation and equilibraation period. Rice husk charred at 700 oC was able to raise pH from 4.2 to 5.0 Ankasa Series and 4.9 to 5.8 in Tikobo Series within the incubation period. All the xvi University of Ghana http://ugspace.ug.edu.gh biochar types reduced Al concentration from 0.4 cmol/kg to undetectable levels in the Tikobo Series with the element being reduced from 1.31 cmol/kg to 0.45 cmol/kg in the rice husk and corn cob at 700 oC biochar amended Ankasa soils within the six-week equilibration period. Soya bean nodulated in the rice husk biochar charred at 700 oC amended Tikobo Series without any form of synthetic fertilization. There was no nodulation in the Ankasa series. Shoot P uptake of soya bean was 1.5 and 1.4 times more in Ankasa and Tikobo Series, respectively when amended with rice husk biochar charred at 700 oC than the same soils amended with conventional lime and equivalent biochar P from triple super phosphate. Apparent nutrient recovery efficiency was higher in biochar amended soils than the CaCO3 amended soils. The biochar amended soils showed an increase in organic carbon contents. The residual total P increased from 101.4 mg/kg to 257.8 mg/kg when rice husk biochar charred at 700 oC was applied to Tikobo Series whilst there was an increase from 164.0 mg/kg to 344.9 mg/kg when corn cob biochar charred at 500 oC was added to Ankasa Series. There was high increase in residual available P after amending the soils with the liming materials. The study concludes that corn cob and rice husk biochar can be used as liming materials and P source in acid soils, particularly Tikobo Series for growth of soya bean. xvii University of Ghana http://ugspace.ug.edu.gh CHAPTER ONE 1 INTRODUCTION Background Soils of Ghana apart from the notable variants of the Vertisols and the salt affected soils on the eastern coast are generally low in bases. The low base saturation is as a result of intense weathering and high rainfall. The high rainfall has led to leaching of bases culminating in the exchange sites of the soils being dominated by H+ and Al3+ and its species. The soils in Ghana, are consequently, mainly Alfisols, Ultisols and Oxisols (Effland et al., 2009). These soils are generally low in primary minerals and consequently low in Ca and Mg (Buri et al., 2005). High temperatures in Ghana have led to fast mineralization rates and coupled with the use of fire as a land clearing method, gains from organic matter additions are short lived. Maintenance of soil fertility in the past three decades has been through the use of inorganic fertilizers, particularly sulphate of ammonia, albeit in low application rates in Ghana (Buri et., al., 2005). An oxidation of a mole of NH +4 leads to the production of two moles of H + (Tisdale et al., 1993). Consequently, the application of sulphate of ammonia might have contributed to the acidic pH (pH< 6.0) of the majority of soils in Ghana (Buri et al., 2005; Oppong, 2011). Soils with low pH are no longer restricted to the deciduous and semi deciduous forest belts and especially to the Western Region. Acid soils now occur extensively in lowlands occupying over a million hectares in Ghana (Buri et al., 2005). A majority of crops in Ghana are presently being grown in soils of pH below 6. According to Sparks (2003), acid soils are generally found in highly weathered areas where rainfall surpasses evaporation and plant use. These soils are characterized by prolonged leaching of basic 1 University of Ghana http://ugspace.ug.edu.gh cations over long period of time with the exchange sites dominated by acidic ions leading to low pH (Tisdale et al., 1993). These soils are inherently low in fertility with high concentrations of Fe and Mn, high toxic levels of Al3+ and low P and Mo (Brady and Weil, 2002). Marine fish catches in Ghana are decreasing as a result of illegal fishing methods such as pair trawling, use of unapproved nets and use of light (Nunoo et al., 2015). Fresh water fish catches have equally dwindled mainly because of the menace of illegal mining activities referred to as ‘’galamsey’’, which tend to pollute river bodies. Eutrophication has also resulted in the growth of aquatic weeds depleting fish stocks in fresh water bodies (Naylor et al., 2000). There is also low production of ruminants due to high incidence of tsetse flies, poor animal husbandry and the sparse grassland in Ghana. Game could have been an alternative for protein. However, it is not a reliable source in that, their populations have declined over the years. Also, there is contamination due to the use of poisonous baits in trapping these game (Ogada, 2014). Production of plants-based protein could, therefore, be seen as the panacea to Ghana’s self-sufficiency in dietary protein. There is increased advocacy for production of soya bean by farmers in Ghana as a result of the crop’s multiple uses as a source of livestock and aquaculture feed, and protein and oil for the human diet (Mutegi and Zingore, 2013). Soya bean is an oilseed, which has a significant amount of all the essential amino acids, minerals and vitamins for human nutrition. It has on the average 40% protein, 30% carbohydrate and oil content of 20% (Adu - Dapaah et al., 2004; MoFA and CSIR, 2005). Its high protein content coupled with the fact that it contains all the essential amino acids may, in part, be the reasons behind the recent advocacy for its wide-scale cultivation in Ghana and use as a substitute for animal protein. 2 University of Ghana http://ugspace.ug.edu.gh According to Ugwu and Ugwu (2010), the benefits of soya bean over other grain legumes such as groundnut and cowpea include lower susceptibility to pests and diseases, better storage quality and larger leaf biomass which translate into soil fertility benefit to subsequent crops. Soya bean has the ability to fix between 60 kg and 168 kg of nitrogen per hectare per year under favourable conditions (Rienke and Joke, 2005). Soya bean is non-host plant to Striga. It however, exudes chemical substances that promote the germination of Striga seeds. The germinated Striga seeds die off within a few days because the parasitic plant is unable to attach itself to the host, soya bean. This attribute of soya bean has, therefore, been exploited by researchers and farmers in northern Ghana for the control of Striga in millet, sorghum and maize production (MoFA and CSIR, 2005). Growth and nodulation of soya bean is affected by soil acidity, soil P status and presence of efficient Rhizobia strains. Production of soya bean requires among others, sufficient water supply; between 350 – 750 mm per annum, ideal temperature ranges between 20 oC and 30 oC, phosphorus requirement of 80 – 120 P2O5 kg/ha and pH from 5.5 to 7.0 with an optimum of 6.0 (Assuming- Brempong et al., 2013). However, with the large expanse of soils in Ghana being acidic, it is evident that yields of soya bean would be low. There has to be a conscious effort to manage the soils such that a favourable pH would be created for sustainable and high productivity of the crop. The use of agricultural lime is a potential option for sustainable soils management among the other options for restoring soil health and fertility. Application of agricultural lime is the conventional way of reducing soil acidity. Agricultural lime is any material that contains Ca2+, and/or Mg2+ as cation and OH-, CO 2-, O2-3 or SiO 2- 3 as anion and is capable of raising the soil pH to a desired level for crop production (Brady and Weil, 2002). In agriculture, lime plays a great role in reducing soil acidity and hence favours plant nutrition. Application of agricultural lime reduces Al and Mn 3 University of Ghana http://ugspace.ug.edu.gh toxicity, increases Ca, Mg, Mo and P uptake and improves on plant rooting system (Brady and Weil, 2002). Calcite, dolomite, quick and slaked lime are common liming materials used. Although soils in Ghana are becoming acidic, the use of agricultural lime by farmers is low due to a myriad of reasons, chief of which is the high cost involved in acquisition. The material is also not readily available on the market when needed and when available is mostly not of pure grade. There is also the problem of high haulage cost to remote farm lands because it is not normally available, at fertilizer sales and distribution centres. It is imperative that a suitable alternative is provided to farmers in Ghana if the productivity of the soils and crops, particularly soya bean, are to be increased. Any alternative material that would be appealing to farmers for liming acid soils should be relatively cheaper, readily available and preferably found in close proximity to the farm. The application of biochar to agricultural soils has recently received attention in Ghana as a result of its multiple benefits to soil quality and improved crop yields, as well as the potential of gaining carbon credits by way of carbon sequestration (Berek et al., 2011). Biochar is a carbon rich material produced by pyrolysing biomass such as manure, wood or leaves under limited oxygen (Sohi et al., 2010). Pyrolysis is the thermal decomposition of organic material under restricted supply of oxygen (Lehmann, 2006). This process employed in biochar production is similar to the age old method of charcoal production, which is one of the most ancient industrial technologies developed by mankind (Harris, 1999). Biochar, due to its molecular structure is chemically and biologically more stable compared to the application of the same un-charred biomass added directly to soil (Lehmann and Joseph, 2009). Consequently, it is more difficult for carbon from biochar to be transformed back to CO2, implying storage of carbon for several decades (Lehmann, 2007, Berek et al. 2011,). Biochar, depending on 4 University of Ghana http://ugspace.ug.edu.gh the types can have numerous chemically reactive functional groups, such as carboxylic, hydroxyl and carbonyl compounds that impart on the material’s high adsorptive properties for toxic substances, such as aluminium, and manganese in acid soils. Thus, biochar could be used to remediate the effects of soil acidity (Berek et al., 2011). The persistence of biochar carbon form in soil would give the material an added advantage should it be exploited for use as a liming material. Lehmann and Joseph (2009), have indicated that the kind and rate of reactions such as adsorption, desorption, precipitation, dissolution and redox reactions that occur in the soil amended with biochar are governed by factors such as pyrolysis temperature, type of feedstock, surface area of biochar, soil properties, and local environmental conditions. Rondon et al. (2007) and Van Zwieten et al. (2007) noted positive plant responses due to increased soil pH as a result of biochar addition. The ability of biochar to maintain pH is related to its liming value. (Van Zwieten et al., 2007). A 30% to 40% increase in wheat height has been recorded on addition of biochar produced from paper mill sludge applied at a rate of 10 t ha–1 to an acidic soil (Van Zwieten et al., 2007). Addition of biochar also increases organic matter content of the soil which affects ion exchange capacity, plant nutrient retention, increase water holding capacity, reduces bulk density and improve soil structure (Gaskin et al., 2007). Sam (2014) has noted that biochar from rice husk and cocoa pod husk charred at 450 oC has available P concentrations of 531 mg/kg and 3897 mg/kg, respectively. Biochar could therefore be exploited for use as a liming material with an added advantage of being a P source. 5 University of Ghana http://ugspace.ug.edu.gh Problem Statement Production of soya bean requires among others; 80 to 120 kg P2O5/ha and soil pH between 5.5 and 7.0 with an optimum of 6.0 (Assuming-Brempong, et al., 2013). However, the majority of soils in Ghana have pH below 6.0 (Buri et al., 2005; Oppong 2011;). Phosphorus is an important nutrient for growth and nodulation of soya bean. A majority of the highly weathered soils of Ghana abound in kaolinite and oxides of Fe and Al (Nartey et al., 1998). With the low pH of these soils coupled with their low organic matter contents, P availability is also very low especially in the concretionary soils of northern Ghana on which a bulk of soya bean is currently being cultivated (Nartey et al., ;1998; Abekoe and Sahrawat, 2001). Hence, increasing the productivity of these soils for soya bean cultivation, would require amendment that will not only raise the pH but also provide available P. Biochar could be the panacea for the low pH and low P availability problem of Ghanaian soils. There is abundance of farm waste such as rice husk, cocoa pod husk and corncob which could be charred anaerobically to produce biochar. However, the feedstock and charring temperature which would produce an ideal biochar for use as a liming material and provide available P for use on acid soils of Ghana has received little attention. Equilibration time or how long a farmer should wait upon amendment of biochar to an acid soil before sowing or planting has not been investigated. Justification Soya bean, among other legumes, contains all the essential amino acids and can be used as a substitute for animal protein in human diet and also to feed livestock (Reinke and Joke, 2005). 6 University of Ghana http://ugspace.ug.edu.gh Presently, Ghana is not self-sufficient in dietary protein as there are inadequate and unreliable sources of protein to meet the ever growing demand of the inhabitants of the country. This is not denying the fact that most of the protein in diets of people living in Ghana are from animal sources which are largely imports from outside the country. Ironically, animal sources of protein are low in fibre content, very high in essential amino acids, and when consumed by humans induce high circulating levels of trimethylamine N-oxide (TMAO), a substance that causes inflammation of the lining of blood vessels and therefore fraught with health hazards such as high cholesterol contents (Tang et al., 2013). Soya bean has become a major source of high quality and cheap protein source for the poor and rural households in West Africa (IITA, 2009). It is low in cholesterol and has the unique property of being a plant source of protein with the complement of all the essential amino acids ((Lokuruka, 2010)). It is thus used to fortify various traditional foods such as gari, sauces, stews, soups, banku and kenkey to improve their nutritional, particularly protein content in Ghana (MoFA and CSIR, 2005). Soya bean can, therefore be conveniently used as a substitute for animal protein. Consequently, the Ghana’s Ministry of Food and Agriculture has for the past two decades been promoting the production and consumption of the crop and this has resulted in rapid expansion in production (Sarkodie-Addo et al., 2006). Despite its numerous benefits, yield of soya bean in West Africa and in Ghana is very low with an average of 1.1 Mg/ha (IITA, 2009). The low productivity in Ghana among others includes low soil fertility of which low pH and low P are the primary factors. Any intervention that would improve on the soil conditions for cultivation of soya bean in Ghana must include amelioration of the acid soils and/or making P more available. 7 University of Ghana http://ugspace.ug.edu.gh Corn cob and to a lesser extent rice husk are agricultural waste which abound in virtually all the ten regions of Ghana. There are ‘’mountains’’ of rice husk at the rice milling centres in the country because the resource is of limited use to farmers and the mills. The material is therefore left in the open to breed rodents which in turn attract snakes. Corn cob apart from being used as fuel source is also left in the open or sent to garbage grounds after shelling. These two organic resources are hardly added as organic amendment to soils probably because of their high C: N ratio and therefore slow decomposition rates. These feedstock types are mainly disposed of by aerobic burning which increases the greenhouse gas (CO2) concentration in the atmosphere. Thermal decomposition of these feedstocks through pyrolysis would convert the organic C into a recalcitrant form to persist for many years in soils. Thermal decomposition could also hasten the liberation of bases from cell walls which may combine with anions like carbonates to form cheap liming materials (Van Zwieten et al., 2007). The charred feedstock could also produce a cheap source of P (Sam 2014; Tetteh, 2014), an important nutrient needed for nodulation, pod formation and root extension in legumes but which is deficient in Ghanaian soils. The high pH of the charred material could also help in ameliorating the acid problems of the soils and also reduce Al toxicity in extremely acid soils (Van Zwieten et al., 2007). Pore spaces in biochar have been found to serve as sites for microbial proliferation to help in nodulation (Dias et al., 2010). It is, therefore, being postulated that with its high inherent available P which is an energy source for microbes coupled with the liming effect, addition of biochar to acid soils would provide an enabling environment for the proliferation of rhizobia to help in the growth and nodulation of soya bean. Production of biochar especially from rice husk could help 8 University of Ghana http://ugspace.ug.edu.gh reduce the garbage collection problem that has bedeviled Ghana as a country and reduce CO2 emission into the atmosphere. Objectives It is in the light of the above that this work seeks to; i. ascertain the liming potential of corn cob and rice husk biochar types on typical acid soils in Ghana ii. ascertain the influence of rice husk and corn cob biochar as liming materials on the growth and nodulation of soya bean. iii. determine the suitability or otherwise of biochar as a P source for the growth and nodulation of soya bean on typical acid soils of Ghana Hypothesis Ho: Addition of corn cob or rice husk biochar will neither reduce the soil acidity nor improve growth and nodulation of soya bean on acid soils in Ghana. HA: Addition of corn cob or rice husk biochar will reduce the soil acidity and consequently improve growth and nodulation of soya bean. 9 University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO 2 LITERATURE REVIEW Definition of pH The availability of nutrients and therefore the fertility and productivity of agricultural soils chiefly depend on the pH of the soil. Soil pH is the level of hydrogen ion concentration or activity in the soil system. It measures the degree of soil acidity or alkalinity. As H+ ion concentration increases, pH value decreases and hence soil acidity increases (USDA, 1999). There are descriptive terms associated with soil pH. Unlike the pure system where neutrality is at seven, the range of between 6.1 and 7.3 on the pH scale is considered neutral in soil (USDA, 1999). Table 2.1 gives the descriptive terms of pH ranges in soils according to the USDA system. Causes of Soil Acidity About 25% of the earth's croplands are affected by problems associated with soil acidity (Graham et al., 2000). It is therefore, worth knowing the causes of acidity if effective remedial measures are to be taken. Soil acidity is caused by several natural and anthropogenic factors. The natural factors include leaching of bases as a result of excessive rainfall, plant uptake of basic nutrients, decomposition of organic matter whilst the anthropogenic causes include application of inorganic fertilizers mainly the ammonium based ones. Generally, soil acidity increases as rainfall increases. 10 University of Ghana http://ugspace.ug.edu.gh Table 2. 1: Descriptive Terms Associated with Soil pH pH ranges Descriptive Term < 4.0 extremely acid 4.1 – 5.0 very strongly acid 5.1 – 5.5 strongly acid 5.6 – 6.0 moderately acid 6.1 – 7.3 neutral 7.4 – 8.0 slightly alkaline 8.1 – 9.0 alkaline > 9.0 strongly alkaline Source: USDA (1999). 11 University of Ghana http://ugspace.ug.edu.gh Soil acidity deals with the H+ ions in soil solution, thus high H+ ion concentration will result in lower pH value and hence higher acidity. Some sources of H+ in soils include: i) Carbon dioxide released from plant roots and microbial respiration which combines with soil water to produce carbonic acid. This acid then dissociates to release H+. CO + H O H CO HCO - + H+2 2 2 3 3 [2.1] (ii) Decomposition of organic matter with concomitant releases of H+. (iii) Roots of plants also release H+ and organic acids to lower the pH of soils. (iv) Nitrification of ammonium NH +4 + 2O2 NO - 3 + 2H + + H2O [2.2] (v) Hydrolysis of Al in soils releases large quantities of H+ into soil solution as shown in the equations below. Al3+ + H O Al(OH)2+2 + H + [2.3] Al(OH)2+ + H2O Al(OH) + + H+ [2.4] Al(OH)+ + H2O Al(OH)3 + H + [2.5] A summary of the three reactions is thus Al3+ + 3H2O Al(OH)3 + 3H + [2.6] 12 University of Ghana http://ugspace.ug.edu.gh (vi) Oxidation of sulphur compounds in soils leads to acidification as depicted in equation S0 + 3/2 O2 + H2O H2SO4 [2.7] S0 is elemental sulphur Types of Soil Acidity There are three general pools, or types of ac idity: active, exchangeable and residual Active Acidity Active acidity indicates the H+ ion concentration in soil solution and it determines the pH of the soil. The active pool of hydrogen ions is in equilibrium with the exchangeable hydrogen ions that are held on the soil’s cation exchange complex (CTAHR, 2007). It is a very small part of the total acidity of a soil. However, it is very important to the plant since it determines the solubility and availability of many elements and nutrients in the soil solution. Active acidity can be directly determined using a pH meter (CTAHR, 2007). Exchangeable Acidity Exchangeable acidity is due to the exchangeable acidic cations Al3+ and H+ on the colloidal surface of soils. When the CEC of a soil is high but has a low base saturation, the soil becomes more resistant to pH changes (CTAHR, 2007). When salt such as KCl or CaCl2 is added to the soil, the cations Al3+ and H+ at the exchange site are released into soil solution by exchanging with K+ or Ca2+. The Al3+ released undergoes hydrolysis to produce more H+ into soil solution as depicted in equation [2.6]. This then lowers the soil pH. Due to the fact that basic cation, K+ or Ca2+ in the 13 University of Ghana http://ugspace.ug.edu.gh salt displaces the acidic cations into soil solution, the name exchangeable acidity is used. This type of acidity is greater than the active acidity. Application of agricultural lime targets the replacement of the exchangeable acidity with basic cations, usually Ca2+ and Mg2+ (Brady and Weil, 2002). Residual Acidity This is the acidity due to Al3+ and H+ bound to clay and organic matter to form complexes that are non-exchangeable and least available (CTAHR, 2007). This form of acidity is greater than either active or exchangeable acidity. Combination of the three types of acidity gives the total acidity soils. Effect of Soil Acidity on Nutrient Availability and Plant Growth The influence of soil pH on growth of plants is mostly indirect, through its impact on chemical reactions and biological processes. According to Giller and Wilson (1991), ideal nutrient absorption by most crops occurs at a soil pH within the neutrality range. Plant growth and development can also be negatively affected when soil acidity is not properly controlled (Nduwumuremyi, 2013). Generally, availability of nutrients such as nitrogen, molybdenum, phosphorus and potassium are negatively affected as soil acidity increases (Brady and Weil, 2002). According to Kochian (1995), solubilized rhizotoxic aluminum species in highly acidic soils can inhibit root growth and function in most plants. Pineros et al. (2005) showed that Al toxicity limits plant growth primarily through its adverse effects on growth and development of roots. Aluminium toxicity also increases drought susceptibility and restricts plant access to subsoil nutrients 14 University of Ghana http://ugspace.ug.edu.gh inhibiting the total expression of plant genetic potential (Ownby and Popham, 1990). According to Giller et al. (1998), Al toxicity reduces the agronomic and recovery efficiencies of nutrients. Strong soil acidity restricts the growth and multiplication of soil microorganisms which suppresses plant growth. For example, biological nitrogen fixation by bacteria that live in nodules of legumes, such as cowpea, groundnut and soya bean, are negatively affected in soil with pH below 6. According to Brockwell et al. (1995), there is reduction of nearly 10-3 in number of S. meliloti in soils at pH below 6 compared to those with a pH >7.0. A consequence of the inhibition of microbial growth and multiplication under low soil pH conditions is the slow decomposition of organic matter In highly acidic soils, P is particularly a limiting nutrient. Under extremely to strongly acid conditions such as in Oxisols, there is high concentration of soluble Al3+ and Fe3+ in the soil. Any added P is then precipitated as depicted in equation [2.8] Al3+ + H2PO - + 4 + 2H2O 2H + Al(OH)2H2PO4 [2.8] The freshly precipitated hydroxy phosphates are slightly soluble because they have a great deal of surface area exposed to the soil solution. With time, the precipitated hydroxy phosphate ages and becomes less soluble and therefore unavailable to plants (Tisdale et al., 1993). This decreases P fertilizer use efficiency. In the Oxisols, Ultisols and Alfisols which incidentally are the dominant soils in Ghana, the dominant clay minerals are kaolinites and oxides of Al and Fe (Nartey, 1998). These clay minerals have exposed OH groups which have high affinity for P (Tan, 1998). At low pH, the exposed OH groups in the clay minerals become protonated and subsequently retain added P as in equation 2.9. 15 University of Ghana http://ugspace.ug.edu.gh Al OH +2 + H PO - 2 4 + Al OH 2 H2PO4 [2.9] The phosphate anion may also replace structural OH of the clay to form an inner sphere complex. There is ligand exchange between the H PO -2 4 and the protonated OH. This reaction while reversible binds the anion too tightly to the mineral and availability is very low (Brady and Weil, 2002). Low soil pH also makes availability of Mo, a key nutrient in nodulation, and B very low in soils (Tisdale et al., 1993). Basic nutrients such as K, Ca, Mg and Na also become deficient in plants because of low solubility in acid soils. However, there are toxicities of Fe, Mn, Zn and Cu in plants under acidic soil conditions because of the high solubility of these micro nutrients in soil solution (Tisdale et al., 1993). High soil acidity especially causes high accumulation of toxic heavy metals such as Hg, As, Pb and Cd in crops especially on soils in mining environments and on soils which agro-chemicals are applied (Sparks, 2003) Control of Soil Acidity Breeding and planting of crops that are tolerant to soil acidity have been proposed as an option. It is, however, time consuming and more often than not, certain traits of the crop modified are either lost or suppressed. Breeding and the use of tolerant crops are actually not remedial measures but rather adaptive and or coping strategies (Curtin and Trolove, 2013). This has not been largely effective because of the relatively slow decomposition to release bases and the fact that organic matter acts as a buffer and therefore resists changes in pH (Curtin and Trolove, 2013). Liming to date, therefore, remains the most viable option and has traditionally been used to correct soil acidity and to improve soil productivity (Curtin and Trolove, 2013). 16 University of Ghana http://ugspace.ug.edu.gh According to Brady and Weil (2002), an agricultural lime is any material that contains Ca and Mg as cations in combination with anions such as carbonates, hydroxides, oxides and silicates which are added to acid soils with the sole aim of raising pH. Commonly used liming materials include calcite, dolomite, slaked lime and quick lime as well as basic slag (Brady and Weil, 2002). Mechanisms by which calcite, the most commonly used agricultural lime increases soil pH when applied to a moist soil are depicted in a series of reaction below; (1) water dissolves the material in the soil to produce Ca2+ and hydroxide (OH–) according to the equation 2.9: CaCO3 + H2O Ca 2+ + 2OH– + CO2 [2.9] (2) The released Ca2+ substitutes for Al3+ and H+ at the exchange sites of the soil. (3) The OH– produced from equation 2.9 reacts with Al3+ to form Al(OH)3, and/or H + to form H2O: 3OH– + Al3+ Al(OH)3 [2.10] OH– + H+ H2O [2.11] The Al(OH)3 formed precipitates out of solution raising the soil pH Thus, liming reduces high levels of Al3+ and H+ through the combination with OH– (Tisdale et al., 1993). Superfluous OH– released from lime will raise the soil pH, which is the most noticeable effect of liming. Liming, depending on the material, provides two macro nutrients, calcium and magnesium to the soil. The size of particles and surface area of liming materials control their 17 University of Ghana http://ugspace.ug.edu.gh reactivity rates in soil. The inherent soil pH, the degree of mixing with the soil, and the chemical nature and composition of the material also effect the reaction rate (Brady and Weil, 2002). For example, oxides and hydroxides react faster than carbonates because of the higher solubilities of the former (Brady and Weil, 2002). Adequate soil moisture is required for the reaction to take place (Brady and Weil, 2002). Lime Requirement Lime requirement of a soil refers to the amount of agricultural liming material needed to neutralize the undissociated and dissociated acidity in the range from the initial acid condition to a desired neutral or less acid condition (McLean, 1971). Economically, lime requirement is defined as the mass of liming material necessary to produce maximum economic yield of crops grown on soils of low pH (McLean, 1971). There are different practical methods used to predict the lime application rate required to accomplish an adequate level resulting in elimination of Al toxicity towards plant growth and development. One of the common methods for predicting the lime requirement is to monitor the concentration of exchangeable Al. According to Bell and Bessho (1993), the enrichment of soil with basic ions, especially Ca2+ ions in soil neutralizes exchangeable Al thus enhancing root growth. Hakim et al. (1989), indicated that the optimal lime rate to improve food crops production on Ultisol is about 6 Mg CaCO3/ ha. Over liming, however can occur at rates exceeding 12 Mg/ha. The KCl extraction method is most commonly used although several extracting solutions have been proposed to estimate the extractable Al (Oates and Kamprath, 1983). 18 University of Ghana http://ugspace.ug.edu.gh Types of Liming Materials Limestone is mostly mined and then ground into fine particle sizes to increase the surface area and consequently reactivity. Limestone usually contains CaCO3 and some other impurities. Limestone makes up the majority of lime that is applied to the soil. Ground limestone with less than 6% Mg is known as calcitic limestone and if the limestone has more than 6% Mg it is called dolomitic limestone (Carey et al., 2006).). Burnt lime (quicklime) is ground limestone exposed to high temperatures to eliminate carbon dioxide. Calcium oxide is obtained after the process of heating. Magnesium oxide will only be present if it was a constituent of the ground limestone before heating. Burnt lime reacts quickly with water to produce hydrated lime or slake lime (Ca(OH)2 and release high amount of heat and therefore must be handled with care (Carey et al., 2006). Calcium hydroxide is very reactive because of its high solubility and excessive application to the soil can quickly raise the pH above the desirable point. Its caustic nature causes injury to plants that are already established in the field. Marls comprise sea shell remains and CaCO3. These are used among farmers in the coastal areas. Marls have similar reactivity as ground limestone (Carey et al., 2006). Advantages of Liming in Acidic Soils Liming plays vital role in ensuring maximum yields from many food crops established on soils of low pH. Kaitibie et al. (2002), reported liming as the most widely used technique for rectifying problems of soil acidity. Addition of lime to the soil at the required rate results in numerous soil chemical and biological changes that are beneficial in ensuring maximum productivity of acid soils. The concentrations of soluble aluminum and manganese decrease to non-toxic levels as a result of liming. Increasing pH decreases the availability of Mn, which becomes a major problem 19 University of Ghana http://ugspace.ug.edu.gh in many plants at pH lower than 5.0 (Nduwumuremyi, 2013). Liming improves Ca and Mg content of acid soils. Acid soils are generally deficient in total and available plant phosphorus and this is as a result of significant portions of applied P fertilizer being biologically fixed to oxides of Fe, Al and clay minerals. Liming improves available P content for plant uptake and utilization. At pH ranges between 5.0 and 6.5, soil available P content increases due to the release of P from Al and Fe oxides (Tan, 1998). Microbial properties of soil can be used to ascertain soil quality (Brady and Weil, 2002). Activities of beneficial microbes, excluding fungi which can flourish over a wide range of soil pH, is restricted by soil acidity. Liming enhances multiplication and activities of most microorganisms which then accelerates rate of soil processes such as decomposition of organic matter to release nutrients (Brady and Weil, 2002). Liming also improves nitrogen fixation in by legumes in acid soils. It helps in the production of phytohormones and increases root surface area and enhance absorption of nutrients that are less mobile, for example P and micronutrients such as Mo and B (Brady and Weil, 2002). According to McBride (1994), increasing soil pH improves the complexation of heavy metals in soils. Soil properties such as nature and kind of clay, organic matter status, redox potential, and soil pH are the main determinants of heavy metals bioavailability in soil and hence liming positively assists in reducing heavy metals availability to crop. Calcium released from lime added to the soil was reported by Haynes (1983) to boost plant resistance to many plant pathogens such as Erwiniaphytophthora, R. solani, Sclerotiumrolfsii, and Fusariumoxysporum. Haynes (1984), also stated that calcium combines with pectic chains to form rigid bonds that facilitate the resistance of plant cell walls to enzymatic destruction by pathogens. 20 University of Ghana http://ugspace.ug.edu.gh Soil N2O emissions has been reported to be reduced by liming if soil moisture content is retained at field capacity and has been recommended as option for mitigation (Stevens et al., 1998). Soil pH has a prospective influence on N2O emission pathways, and the transformation of N2O to N2, and it is recommended that liming may serve as an alternative for the mitigation of N2O production from farm lands (Stevens et al., 1998). Biochar Biochar is progressively receiving attention in agriculture as an environmentally-friendly amendment to principally mitigate climate change (Lehmann et al., 2003). Biochar is defined as a very porous material that is high in carbon and which is obtained by thermal combustion of biomass under restricted oxygen conditions and at comparatively high temperatures mostly between 300 0C and 1000 0C (Lehmann et al., 2003). Biochar or black carbon is rich in carbon has a large specific surface area and has been shown to have the ability to increase water and nutrient retention of soils (Lehmann and Joseph, 2009). Biochar as a soil amendment traps carbon from the atmosphere to mitigate climate change. It also enhances productivity of soil by improving water holding capacity, nutrients adsorption and activity of microbes and therefore increasing yield of crops. Charring of feed stocks such as sawdust, animal manure and crop residues to produce biochar helps in recycling of forestry and agricultural wastes (Lehmann et al., 2003). Biochar Production Biochar is obtained by burning biomass with little or no oxygen. This makes it different from actual burning of biomass which involves naked flame and oxygen to oxidize the carbon in the biomass completely to carbon dioxide leading to the production of ashes and small amounts of 21 University of Ghana http://ugspace.ug.edu.gh carbon. Limiting oxygen accessibility leads to high carbon retention in the biomass. Yield of carbon in biochar is usually 50% or less due to the fact that the pyrolysis process also produces combustible gases and volatile compounds from the pyrolyzed biomass (Lehmann, 2007). Heating of biomass under ambient temperatures results in dehydration. Moisture in the biomass is first driven off and this involves the provision of great energy due to high heat capacity of water and large quantity of energy needed to vapourize the water content (Taylor and Mason, 2010). Thus, fresh feed stocks are not ideal for biochar production. The moisture content of biomass should be between 10 and 15% prior to pyrolysis. The torre faction phase in the thermal decomposition process starts when the biomass is dry the biomass is “roasted”, turning dark in colour due to chemical changes. Gases and other volatile compounds are released from the biomass. True pyrolysis starts when the temperature reaches 3000 C, resulting in exothermic reactions. The feedstock fully readjusts itself to form solid biochar releasing volatile compounds and combustible gases (Taylor and Mason, 2010). Pyrolysis process can be fast or slow. The rate of pyrolysis process has a significant impact on the characteristics of the end products. The quality of the product is also dependent on the feed stock type (Taylor and Mason, 2010). Biochar Stability in the Soil Stability determines how long it can support quality of soil and water system (Lehmann, 2007). Biochar can exist in the soil environment for many years more than any other kind of organic amendment containing carbon. Traces of biochar have been found in the soils of the humid tropical 22 University of Ghana http://ugspace.ug.edu.gh climate such as the amazon, many years after application in spite of the speedy rates of mineralization common to organic matter in those environments (Sombroek, et al., 2003). Structural Composition of Biochar Thermal decomposition of cellulose in organic biomass between 250 oC and 350 oC leads to considerable loss of volatile compounds with a concomitant increase in aromatic C concentration. According to Demirbas (2004), water evaporates first, followed by hydrocarbons, tarry vapour, hydrogen gas, carbon monoxide and then carbon dioxide. Thereafter, there is the transformation of alkyl and O-alkyl aryl carbon (Baldock and Smernik, 2002). Consequently, a large mass of amorphous carbon matrix is formed. At a temperature of about 330 oC, there is lateral growth of graphene sheet, at the expense of the amorphous carbon phase and finally coalesce. At temperature above 600 oC, there is the elimination of most of the remaining non-carbon atoms and carbonization becomes the dominant process; a consequence of which is relative increase in carbon content. Carbonization can reach 90% by weight in biochar produced from woody feed stocks (Demirbas, 2004). Chemical Composition of Biochar and Surface Chemistry Carbon, moisture, mineral matter, and volatile compounds are the main components of biochar (Antal and Gronli, 2003). The physical and chemical behaviour of biochar and its function (Brown, 2009) and hence its suitability and fate for a particular application in the environment (Downie, 2009) is determined by its composition. Biochar surfaces show hydrophobic, hydrophilic, acidic and basic properties and these surface properties are governed by the feed stock and pyrolysis temperature. Brennan et al. (2001) stated 23 University of Ghana http://ugspace.ug.edu.gh that the presence of heteroatoms in biochar causes surface chemical heterogeneity mainly as a result of differences in their electronegativity compared to those of carbon atoms. Functional groups such as OH, NH2, O(C=O)R act as electron donors whilst (C=O)OH, (C=O)H and NO2 groups are electron acceptors. Carboxylic functional groups are strong Bronsted acids whereas phenols and carbonyl groups are weak acids with chromenes and pyrones being basic functional groups Brennan et al. (2001). There are vast variations in mineral matter content and their composition on the surfaces of biochars (Tetteh, 2014). Acidic and basic sites may coexist within micrometres of each other on the outer surfaces and pores of the biochar particles (Brenman et al., 2001). According to Chan and Xu (2009), carbon content of biochar irrespective of type is between 172 and 905 g/kg, although organic carbon usually accounts for less than 500 g/kg for different materials. Total nitrogen content of biochar ranges from 1.8 to 56.4 g/kg depending on the type of biomass. The high total nitrogen content may not be available to crops as a result of complexation reactions with mineral nitrogen content less than 2 mg/kg. Studies have shown that carbon- nitrogen ratio vary widely from 7 to 500. Total phosphorus and potassium content of biochar fall between the ranges of 2.7 to 480 and 1.0 to 58.0 g/kg, respectively (Chan and Xu, 2009). Properties of biochar change as it ages in the soil, particularly due to its oxidization and accretion of H+ from the soil solution in the early weeks on amendment to the soil. The extent to which biochar properties change with age depends on the feed stock used to produce it (Heitkotter and Marschner, 2015), soil and prevailing climatic conditions (Cheng et al., 2008). 24 University of Ghana http://ugspace.ug.edu.gh Functional Groups High-mineral ash biochars contain metals in some of the functional groups. Schnitzer et al. (2007) and Koutcheiko et al. (2007) reported a range of different N- and S-based functional groups in biochar produced from chicken manure. Data produced by Elizalde-Gonzalez et al. (2007) indicate that the relative concentration of each of the functional groups depends upon initial composition of the biomass, final surroundings of the charring particle, rate of heating and post-treatment. Biochar interacts readily with atmospheric oxygen to produce oxygen containing functional groups on the surface (Bourke et al., 2007). Swiatkowski et al. (2004) reported that pyrone surfaces may be as a result of the adsorption of molecular oxygen in the form of superoxide ions O2– and the adsorbed O, such as O– or O2–. Biochar obtained from farm manures and sewage sludge contains nitrogen and sulphur functional groups compared to lignocellulosic biochars. Areas of high nitrogen concentration are mostly basic (Bourke et al., 2007). Koutcheiko et al. (2007), prepared chicken manure biochar by heating to 360 oC in a fast pyrolysis unit with no reaction time reported. The biochar was then heated to 800 oC and activated with carbon dioxide. Their results showed that core functional groups containing nitrogen for the low-temperature biochar were pyridinic amines, whereas the high-temperature biochars contained almost equal quantities of pyridinic and quaternary groups. Bagreev et al. (2001) reported a similar pattern when they investigated changes in sewage sludge biochars produced between 450 oC and 900 oC in a fixed bed reactor. Their results at lower temperatures showed that amine functionalities were present while at higher temperatures organic nitrogen was incorporated within the biochar as pyridine-like compounds. Koutcheiko et al. (2007) identified S functional groups in chicken manure biochar with low-temperatures which produced sulphonates 25 University of Ghana http://ugspace.ug.edu.gh and sulphates whilst thiophene and sulphide groups dominated at high temperatures. Knudsen et al. (2004), reported that up to 500 oC, wheat straw biochar had sulphate but at higher temperatures, sulphur was transformed to an insoluble sulphide such as CaS and K2S. Functional groups on biochar may be amphoteric and hence surface charges may change with the pH of the solution. Thus, in acidic conditions, the surfaces are protonated, whilst in alkaline conditions, the surfaces are deprotonated. Biochar as Liming Material Many research reports on pH of biochar have shown that they are mostly neutral to basic in soil reaction. Thus, their applications have been found to increase soil pH (Joseph et al., 2010). According to Verheijen et al. (2010), the liming property of biochar is one of the most likely mechanisms behind increases in crop yield when it is used as soil amendment. The amendment of biochar on tropical soils has resulted in reduced aluminium toxicity by decreasing the acidity (Verheijen et al., 2010). Noble et al. (1996), reported the liming effect of agricultural wastes and other biomass when charred and applied to the soil. Farrell et al. (2013) and Masto et al. (2013) reported an increase in soil pH after application of biochar on different types of soils, which is attributed to the temperature during pyrolysis and type of feedstock. According to Yuan et al. (2011) decarboxylation of organic anions as exhibited by excess cations contained in biochar consumes H+ and therefore increases the soil pH. Alternatively, the presence of negatively charged functional groups such as phenol, carboxyl and hydroxyl on biochar surfaces adsorb H+ from soil solution thereby lowering its concentration with a consequential rise in soil pH (Brewer and Brown, 2012; Chintala et al., 2014). 26 University of Ghana http://ugspace.ug.edu.gh Silicates, carbonates and bicarbonates emanating from biochar also form complexes with H+ ions and making the proton unavailable to the soil solution (Brewer and Brown, 2012; Chintala et al., 2014). The influence of biochar in increasing soil pH is more pronounced in acidic soils and in soils with low organic matter status (Stewart et al., 2013). Soils with high organic matter content resist change in pH on application of biochar due to the buffering capacity of organic matter (Curtin and Trolove, 2013). Increases in the variable charges of soils by biochar improve their cation exchange capacity (Chan et al., 2007; Nelissen et al., 2012; Taketani et al., 2013) this is due to the fact that leaching of base cations is reduced as adsorption of H+ ions to negatively charged functional groups of biochar, organic matter, and organo-mineral complexes is enhanced. However, the intensity of this impact may be governed by the soil organic matter content, which is the principal determinant of soil cation exchange capacity (Brady and Weil, 2008). Mode of Biochar Application The behaviour and fate of biochar materials in the soil and the environment as a whole is influenced by the method of its application to soils (Verheijen et al., 2010). There are three main methods of biochar application viz; i) topsoil application, ii) depth application, and iii) top-dressing. Topsoil Application Topsoil application of biochar can be done by either applying it alone or mixing with composts or manures at the surface of soil. The light mass and powdery nature of biochar makes its surface 27 University of Ghana http://ugspace.ug.edu.gh application prone to erosion by both water and wind (Verheijen et al., 2010). It is for this reason that top soil application of biochar is normally done in conjunction with compost (Verheijen et al., 2010). Depth Application Under conventional farming practice, biochar and compost are commonly mixed more or less uniformly in the entire topsoil to about 30 cm depth. Application of biochar mixed with compost or manure helps to reduce erosion of biochar by wind and water (Verheijen et al., 2010). In conservation farming systems, the deep incorporation reduces the risk of erosion which results in higher biochar concentrations at equal rate of application (Verheijen et al., 2010). Deep mouldboard ploughing helps in depth application with additional topsoil homogenization occurring during subsequent ploughing and or harrowing (Blackwell et al., 2007). The placement of the biochar directly into the rhizosphere seem to be more advantageous for crop growth and less prone to erosion (Verheijen et al., 2010). The application can be either by pneumatic systems, which can function at high rates, or by adding the biochar in trenches and levelling the soil surface afterwards (Verheijen et al., 2010). Successive mouldboard ploughing and tilling further homogenizes the biochar distribution throughout the topsoil (Blackwell et al., 2007). Top Dressing Top-dressing of biochar is the spreading of biochar which is mostly dust at the soil surface and hoping that natural processes would incorporate the it into the topsoil ((Blackwell et al., 2007; Verheijen et al., 2010). Top dressing is considered chiefly under circumstances where mechanical incorporation is not possible, as in no-till systems, and pastures (Blackwell et al., 2007). A major 28 University of Ghana http://ugspace.ug.edu.gh setback of this mode of application is the possibility of the material being eroded by water and wind, as well as human inhalation. There are also no ideal rates of application for different soil- climate-land use systems. The dust fraction of biochar is an issue during storage, handling, and at the applying stages regardless of the method used (Verheijen et al., 2010) Agronomic Importance of Biochar Addition of biochar enhances plant growth and development, crop yields and increases production of food and sustainability in marginal soils with low organic matter, inadequate water and poor nutrient status (Lehman et al., 2006). Due to the fact different soils react differently to the application of the biochar, it takes some time to compare responses of soils (Lehman et al., 2006). The ideal biochar application rate depends on the soil type and the crop management system (Verheijen et al., 2010). Application of biochar is considered a novel approach to establish sink for atmospheric carbon dioxide in terrestrial ecosystem (Lehman et al., 2006). In addition to the positive influence in reducing emissions and increasing the sequestration of greenhouse gases, biochar production and application to the soil provides immediate benefits through enhanced soil fertility and increased crop production (Lehman et al., 2006). Southavong et al. (2012), indicated that biochar may be an immediate answer for managing agricultural waste. The positive plant responses to the application of biochar has been attributed mainly to direct supply of nutrients with very little consideration given to other biochemical factors that may affect nutrient availability (Lehmann et al., 2003; Chan et al., 2007 and Van Zwieten et al., 2007). The positive responses as a result of application of biochar were attributed to either nutrient retention as in fertilizers or enhanced fertilizer-use efficiency and therefore can be viewed as an indirect nutrient value of biochars. Rondon et al. (2007), and Van Zwieten et al. (2007) reported the plant 29 University of Ghana http://ugspace.ug.edu.gh responses to increased or stable pH as a result of biochar application. Hoshi (2001) concluded that 20% increase in height and 40% increase in volume of tea trees were partly due to the ability of biochar to maintain the pH of the soil. The ability of biochar to maintain pH is related to its liming value. Van Zwieten et al. (2007) recorded almost 30% to 40% increase in wheat height when biochar produced from paper mill sludge was applied at a rate of 10 t ha–1 to an acidic soil. They concluded that the carbonates in the biochar promoted wheat growth by overcoming toxic effects of exchangeable aluminium contained in the acidic soils. Other explanations given for positive responses to biochar application that are not connected with plant nutrition included toxin neutralization (Wardle et al., 1998), enhanced soil physical properties such as increase in water-holding capacity (Eswaran et al, 1980), and reduced soil strength (Chan et al., 2007). Also, dry matter yield increased by 26% when N fertilizer was also applied at 100 kg N/ha in addition to biochar compared to a control that received the same amount of N without biochar. Biochar application increased N fertilizer-use efficiency of radish and this was attributed to the improved soil physical properties which included, reduced soil strength and higher water holding capacity. Furthermore, Lehmann et al. (2003), also reported the ability of biochar to hold applied fertilizer and reduced leaching resulting in increased fertilizer-use efficiency. This ability is due to the high charge density and high surface area of biochar. Lehmann (2007), reported the significant improvement in plant productivity and soil quality and also environmental benefits such as reduced pollution due to reduced fertilizer losses through leaching when biochar was applied. 30 University of Ghana http://ugspace.ug.edu.gh Importance of Biochar in the Environment Sequestration of Carbon Carbon sequestration is defined as the capture and subsequent storage of carbon that would otherwise be emitted to or remain in the atmosphere into plants and soils (FAO, 2008). Large quantities of carbon in biochar can be sequestered in the soil for thousands of years (Lehmann et al., 2006). According to Marris (2006), about 250 ha farm could sequester approximately 1900 tons of carbon dioxide per annum. Carbon sequestration in plant and soil systems suggests greater opportunity for mitigating the greenhouse effect (Lal, 2004). Biochar has recalcitrant carbon which can resist degradation (Schmidt and Noack, 2000). This property of biochar makes it essential for major carbon sink. With respect to other terrestrial sequestration techniques, biochar has a higher potential to increase carbon storage time more than afforestation (Ogawa et al., 2006). Biochar application resulted in decreased emission of nitrous oxide and methane (Duku et al., 2011). Impact on Soil Performance and Resource Implications Interactions among soils, biochar, microorganisms and root of plants start occurring within a short time after biochar application (Lehmann and Joseph, 2009). Glaser et al. (2002) indicated that water retention in biochar amended soil is 18% higher than in adjacent soils with little or no biochar amendment. The stable macro pore structure of biochar is in part responsible for improving on a soil’s water holding capacity (Brodowski et al., 2007). The large specific surface area and high cation exchange capacity of biochar has accounted for its very high sorption capacity for cations (Gaskin et al., 2007). The specific surface area of biochar increases as temperature increases due to creation of more micropores (Bird et al., 2008), and great 31 University of Ghana http://ugspace.ug.edu.gh quantities of carboxyl groups on the surfaces. Cheng et al. (2006) suggested that increases of carboxyl groups on char surfaces with time, is in part due to either partial oxidation of open surfaces by biological and non-biological processes and/or chemisorption. The inherent stability of biochar creates a difference between the cation exchange capacity that it provides, and that from soil organic matter. There is no apparent restriction on the quantum of benefit that could be achieved with repeated addition as there is incremental enhancement of cation exchange capacity. Biochar has the capacity to remove nitrate and phosphate from water (Mizuta et al.,2004; Eduah, 2009). Biochar may loosely hold nutrient elements in a bio-available form which is of importance to crop growth and also has instituted affinity for organic compounds and may sorb toxic substances in the soil (Yu et al., 2006). Indirect influence of biochar on the chemistry of the soil seem to arise from amendment of soil pH. Studies show that terra preta sites have higher pH and phosphorus than surrounding soils. The ash component of biochar has more available forms of nutrients than the uncharred biomass. The indirect effect of biochar on phosphorus availability in the soil and the mineral ash of its matrix containing phosphorus, potassium and other potentially important micronutrients are essential in explaining its short-term influence on crop growth (Lehmann and Joseph, 2009). According to Steiner et al. (2008) microbial activity in soil is enhanced on addition of biochar. Sam (2014), also found out that degradative abilities of heterotrophs were enhanced when cocoa pod husk biochar was amended to atrazine and paraquat contaminated soils. There is comparatively extensive literature supporting stimulation of indigenous arbuscular mycorrhizal fungi by biochar, and this has been associated with enhanced plant growth (Rondon et al., 2007). Microbial structure in soil that contains aged biochar is distinctively different from those in which 32 University of Ghana http://ugspace.ug.edu.gh fresh biochar has been amended (Kim et al., 2007). Microbial populations react initially with labile components of biochar on its amendment to soil and pyrolysis condensates seem to promote microbial activity in the soil (Steiner et al., 2008). Biochar and Nitrogen Fertilizer Interactions Integrated crop management which includes the application of organic manure and some other organic materials is the technology used for increasing fertilizer use efficiency (Fageria and Baligar, 2005). Organic matter added to soil decomposed at faster rate under wet tropical environment compared to the charred biomass. Biochar is more recalcitrant when applied to the soil but enhances utilization of nitrogen from applied inorganic fertilizers (Steiner et al., 2007 and Widowati et al., 2011). This is due to the reduction in nitrogen loss as a result of increased cation exchange capacity of soil with biochar application (Chan et al., 2008) and also its capacity to inhibit ammonium transformation to nitrate released from fertilizer (Widowati et al., 2011). Negative Effect of Biochar Applied to the Soil McClellan et al. (2007) reported several instances of reduced plant growth as a result of biochar application due to the temporary high levels of pH and volatile nutrient imbalances associated with it when applied fresh. Mostly, biochar has an initial alkaline pH which is favoured for application to soils with low pH. When applied to alkaline soils, however, plants experience nutrient deficiency particularly basic cations and P. High pH of soils due to biochar addition may also cause NH3 volatilization when ammonium-based fertilizers or organic manures are applied. Tars, resins, 33 University of Ghana http://ugspace.ug.edu.gh and other short-lived substances that remain on the biochar surface immediately after production can hinder growth of plants (McClellan et al., 2007) Biochar adsorbs chemicals such as pesticides and also organic matter making these compounds inaccessible to microbial and enzymatic degradation (Kookana et al., 2011; Zimmerman et al., 2011). Kookana et al. (2011) also revealed that some biochar products may be toxic to plants and soil micro fauna. Origin and History of Soya bean Soya bean, Glycine max is a legume from the family Leguminaceae. The plant is thought to have originated from the far East i.e. China, Korea and Japan, from where it spread to other regions of the world (Ngeze, 1993). There is evidence to show that it was used as food and as constituent of medicine in China over 500 decades ago (Norman et al., 1995). Other investigators have suggested Australia and Eastern Africa as possible centres of origin of soya bean (Addo-Quaye et al., 1993). There is commercial production of soya bean in both the temperate and tropical environments such as China, Thailand, Indonesia, Brazil, USA and Japan; where it has become a major agricultural crop and an essential export commodity (Evans, 1996). According to Ngeze (1993), soya bean was introduced to Africa via Southern Africa in the early 19th century. It was brought to Ghana by the Portuguese missionaries in 1909. According to Mercer-Quarshie and Nsowah (1975), early introduction of the crop failed because it originates from the temperate zone. Collaborative efforts between Ministry of food and Agriculture, Ghana and the International Institute of Tropical Agriculture (IITA) culminated in successful production of the crop in Ghana in the early 1970s (Tweneboah, 2000). 34 University of Ghana http://ugspace.ug.edu.gh Importance of Soya bean Soya bean has several benefits. It serves as source of food for both human beings and livestock (Borget, 1992). Soya bean has several nutritional and medicinal qualities and also industrial and commercial uses, and agricultural benefits (Osman, 2011). As reported by Dugje et al., (2009), soya bean is more protein-rich than any other legume food sources in Ghana with average protein content of about 40%. Oil content of Soya bean seeds is about 20% on dry matter basis, and it is 85% unsaturated and cholesterol-free. Soya bean can be eaten in various forms such as a vegetable and can also be processed into soy oil, soy milk, soy yogurt, soy flour, ‘tofu’ and ‘tempeh’ (MoFA and CSIR, 2005). Rienke and Joke (2005), reported that soya bean contains all the essential amino acids and is an essential source of carbohydrates, oil, vitamins and minerals. It is cheaper on per mass basis than an equal amount of meat or eggs (Ngeze, 1993). It can, therefore, be a perfect substitute for meat in developing countries, where animal protein food sources such as meat, fish, eggs and milk are mostly scarce and expensive especially for the poor (MoFA and CSIR, 2005). Because of its low cholesterol but high fibre content and high quality of protein, it is seen as a healthy food to prevent diabetes and high blood pressure. There is evidence that consumption of soya bean reduces the risk and incidence of cancer and diabetes. Its high Ca content is exploited for the treatment of ostersporosis (Lokuruka, 2010). The cake obtained as bye-product from soya bean oil extraction is also an important source of protein feed for poultry, pig and fish. The extension of soya bean production has led to significant growth of the poultry, pig and fish farming (Ngeze, 1993; MoFA and CSIR, 2005). Dugje et al., (2009) showed that haulms after extraction of the seeds can also provide good feed for sheep and 35 University of Ghana http://ugspace.ug.edu.gh goats. Soya bean can fix between 60 kg and 168 kg of nitrogen per hectare per year under favourable conditions (Rienke and Joke, 2005). It is thus a good source of N for subsequent plants in a rotation. The matured green parts are used for compost preparation. Factors that Affect Growth and Yield of Soya bean The growth and development of the soya bean plant is largely influenced by both biotic and abiotic factors. These factors include soil microbes, soil water characteristics and availability of plant nutrients, climate, pest and disease infestation, cultivation and management practices. Optimum climatic growing conditions include average temperatures ranging from 20 °C to 30 °C. The crop does not perform well at temperatures below 20 °C and over 40 °C. The ideal rainfall is between 350 and 750 mm, which is well distributed over the entire growth season (Ngeze, 1993) Soya bean can withstand a wide range of soil conditions but performs best on warm, moist, and fertile loamy soils of good drainage and adequate nutrients (Hans et al., 1997). According to Ngeze (1993), soya bean does well in fertile soils with pH of between 5.5 and 7.0. It is comparatively a better acid tolerant crop than any other legumes. It however, does not flourish in alkaline, saline and reduced soils. Soya beans can only withstand a little water logging conditions (Norman et al., 1995). Ensuring soil pH between 5.5 and 7.0 improves the availability of nutrients such as nitrogen and phosphorus, microbial degradation of crop residues and symbiotic nitrogen fixation (Ferguson et al., 2006). Soya bean requires adequate moisture for seeds to germinate and develop. 36 University of Ghana http://ugspace.ug.edu.gh Nodulation Several leguminous plants have established symbiosis with nitrogen-fixing soil-bacteria collectively identified as rhizobia such as those in the genera Mesorhizobium, Azorhizobium, Rhizobium, Allorhizobium, Bradyrhizobium, and Sinorhizobium (Ferguson et al., 2013). Root infection usually involves the development of infection threads. Rhizobia enter the roots of compatible legume plants resulting in the formation and the development of specialized root structures known as nodules (Oldroyd et al., 2011). Nitrogenase enzyme complex of rhizobia in the nodules reduces atmospheric nitrogen, which is an unusable form into plant available ammonium for growth and development (Cullimore and Bennet, 1992). According to Ferguson et al. (2013), formation of nodules and fixation of nitrogen require great amount of energy (ATP) and are therefore strongly regulated to ensure a balance between nitrogen acquisition and energy spending. Phosphorus is thus a major nutrient required for growth and nodulation of legumes in general. Thus its deficiency markedly suppresses nodulation Many nitrogenous compounds are strong inhibitors of nodule formation. Legume plants have evolved a mechanism to detect nitrogenous compounds in the soil, particularly, the plant available forms, nitrate and ammonium. The higher the levels of these compounds in the soils, the lower the nodulation. Several factors control the nodulation of legumes and these include availability of nutrients such as P, N and Mo. Other soil factors such as temperature, moisture content and pH also affect nodulation (Ferguson et al.., 2013). 37 University of Ghana http://ugspace.ug.edu.gh Soil Temperature Temperature has noticeable effect on the survival and proliferation of rhizobial strains in soils. The influence of temperature on rhizobia seems to depend on soil type and strain. For example, R. leguminosarum bv. trifolii performed better than Bradyrhizobium sp. at high soil temperatures (Mohammadi et al., 2012). According to Triplett and Sadowsky (1992), high soil temperature - induces delay in nodulation or restricts nodulation to the sub-surface soils. Aranjuelo et al. (2007) revealed that plant and nodule dry mass are affected by temperature. Hungria and Franco (1993) also reported that high-root temperatures reduced infection, N2- fixation ability, and legume growth but this is also dependent on rhizobia strain type and strain and cultivar interactions (Arayankoon et al., 1990). Various legumes and Rhizobia combinations have their optimum temperature relationships between 35 to 40 °C for soya bean, peanut and cowpea. Soil pH Stress Soil pH governs most chemical and biological processes that occur in the soil system. The impact of soil pH on nodulation has been investigated extensively due the large expanse of acid soils in the world. Low soil pH creates conditions that hinders plant growth and development that directly causing poor growth. Growth of legumes may be adversely affected by soil acidity through reduction of nodule formation and nitrogen fixation. Generally, different rhizobia strains differ in their tolerance to soil acidity than host plant (Mohammadi et al., 2011) Nodules formed by the rhizobia under low pH conditions may be ineffective or fix insufficient nitrogen (Graham et al., 2000). Rhizobia have pH ranges within which they can function, only few can thrive in pH between 4.5 and 5.0. Micro-symbiont seems to be more pH sensitive than the host 38 University of Ghana http://ugspace.ug.edu.gh (Hungria and Vargas, 2000). According to Hungria and Vargas (2000), nodulated legumes are less tolerant to Mn and Al toxicity which are in turn controlled by soil solution pH. Soil Water Availability Soil water affects almost all the activities of soil microbes including their growth and metabolic processes in the soil. Soils with smaller pore spaces provide conducive environments for the growth of soil microbes including rhizobia (Turco and Sadowsky, 1995). Poor nodulation of legumes in arid soils is as a result of decreases in number of rhizobia during the dry season. Rhizobia adapt to osmotic stress by the intracellular accumulation of inorganic and organic solutes (Boscari, 2002). Availability of Phosphorus Availability of P in the soil during seedling development is essential for determining growth, N2 fixation and grain formation of legumes and its shortage can hinder nodulation (Giller, 2001). Nodule formation and function are important sinks for P and nodules generally have the highest P content in the plant (Sinclair and Vadez, 2002). Deficiency of P leads to reduction in nodule formation and application of P fertilizers mostly leads to increased nodule number and dry mass, as well as higher N fixation (Sinclair and Vadez, 2002). According to Yakubu et al. (2010), low soil phosphorus levels suppress rhizobia number and root development in legumes which in turn decreas N2 fixing potential. An increase in whole plant growth and plant nitrogen concentration corresponding to increased soil P supply from 20 to 40 kg P2O5 ha -1 has been observed (Sinclair and Vadez, 2002; Magani and Kuchinda, 2009). 39 University of Ghana http://ugspace.ug.edu.gh Productivity of legumes in Africa is low because farmers do not have access to P fertilizers (Sinclair and Vadez, 2002). Various experiments have shown that recommended rate for P fertilizer in production of legumes should be location specific. Singh et al. (2011) reported significant response to applied P up to 60 kg P2O5/ha with all the varieties of cowpea used in the Sudan Savanna zone of Nigeria. Higher grain yield in cowpea has been credited to higher availability of P that is responsible for effective nodulation and nitrogen fixation (Singh et al., 2011). Study by Asuming-Brempong et al. (2013) have revealed that growing legumes at the coastal savanna zone of Ghana requires phosphorus between 90 and 120 kg P2O5/ha. Vesterager et al. (2008) reported that even though grain yield was not affected, the quantity of N fixed in a cowpea monocrop increased from 58 to 77 kg N/ha and from 30 to 43 kg N/ha in a cowpea intercrop due to P application in the semi-arid zone of Tanzania. Nodulation has been found to decrease with increasing P and N application suggesting an antagonistic effect of readily available N on the functions of P Vesterager et al. (2008). This observation shows that application of P may not optimize biological nitrogen fixation in the presence of readily available N in the soil. Population of Rhizobia Strain in the Soil Rhizobia form symbiotic relationship with legume roots to fix atmospheric nitrogen. As the population of rhizobia increase, the more likely it would be for nodule infection. Soil rhizobia population can be extremely variable in composition and symbiotic characteristics of species (Martins et al., 2003). Native and inefficient rhizobia strains may compete with inoculated efficient species for place of infection on the host plant roots. Nodules made by different strains and different species can occur on the root of the same plant (Moreira and Siqueira, 2006). Legume- Rhizobia symbiosis can sustain agriculture in the tropics at moderate levels of output, provided all 40 University of Ghana http://ugspace.ug.edu.gh environmental constraints to the proper functioning of the symbiosis have been lessened (TSB- CIAT, 2004). Work done by Singleton et al. (1992) showed that less than 60% of tropical soils sampled from Africa had less than 1,000 rhizobia/g soil and 47% with 100 rhizobia/g soil that belong to the cowpea cross-inoculation. Fening and Danso (2002), reported that 68% of rhizobia sampled from 20 Ghanaian soils were moderately effective in nodulating cowpea. Soil Nutrient Soil nutrient status generally has a remarkable influence on the symbiosis and also independent growth and survival of legumes. Nitrogen fixation decreases with increasing legume age, mainly because of the related increase in soil N content. A negative exponential relationship has been observed between N fertilizer rate and N2 fixation (Ledgard and Steele, 1992). Calcium deficiency, with or without the confounding influence of low pH, also affects attachment of rhizobia to root hairs, and nodulation and nodule development (Alva et al., 1990). Calcium plays a pivotal role in symbiotic interactions at the molecular level. Poor nodulation of soya beans in acid soil has been attributed to an Al induced Ca deficiency (Biswas et al., 2003). In addition to macro nutrients, the growth and persistence of rhizobia in soils is also influenced by several other nutritional factors (Brockwell et al., 1995). Supplementation of soil and inoculants with glutamate, glycerol, and organic matter has been shown to enhance the survival and numbers of rhizobia in soils and increase both early nodulation and N2 fixation (Rynne et al., 1994). This result indicates that, although, rhizobia can surely persist in soils, their efficacy can be enhanced by carbon addition, which suggests that they are C limited in the natural state. 41 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE 3 MATERIALS AND METHODS Soils and Sampling Two Oxisols were sampled from the rain forest zone in the Western Region of Ghana. The area has an average annual rainfall of about 2200 mm, mean temperature of 27 0C and relative humidity of about 90% (MoFA, 2012). The soils sampled are Ankasa and Tikobo Series. These soils have been classified by Dwomo and Dedzoe (2010), according to the USDA system as Plinthic Acrudox and Typic Hapludult, respectively. The Ankasa series was sampled from a forest conservation area with no farming record whilst the Tikobo series was sampled from a fallowed land with no known history of legume production at the Council for Scientific and Industrial Research, Crop Research Satellite Station, Ghana. The sampling point of Ankasa Series was located at 50 14. 599’ N and 20 38.453’ W and Tikobo Series at 5o 03.558’ N and 20 28.2825’ W. Disturbed soil samples were randomly taken from the plough layer (0 – 20 cm), bulked, homogenized and sub samples taken for routine characterization and pot experiment. Undisturbed samples were also taken for bulk density determination. The disturbed samples were air-dried and portions were ground to pass through a 2 mm sieve to obtain the fine earth fraction. The remaining soil was not processed (whole soil) and was used for incubation studies and pot experiment in a screen house. Soil Characterisation Physico-chemical analyses of the undisturbed soil samples were undertaken. 42 University of Ghana http://ugspace.ug.edu.gh Total Phosphorus Total phosphorous was determined by digesting 0.2 g of biochar with 25 mL of a mixture of concentrated HNO3 and 60% HClO4 in the ratio of 1:1.5 (HNO3: 60% HClO4). Distilled water was added to the digest, filtered and made up to volume in a 100 mL volumetric flask with distilled water. Phosphorus in the digest was determined as described by the Murphy and Riley (1962) method as outlined earlier in section 3.2.2.4. The P content of the samples in triplicates was then read with the spectrophotometer, and the calculations were done as follows: SP reading x Volume of Extract 106 P (mg/kg) = x [3.14] Volume of Aliquot x Weight of Biochar 1000 Physical Properties The physical properties of the soils measured included bulk density, particle size distribution and moisture content at field capacity. Bulk Density (Core Method) Bulk density was determined using the core method of Blake and Hartge (1986). Core samples were randomly taken from the sampling sites to avoid root disturbance and at the same time representative of the whole area. The soil surface was cleared and a cylindrical metal core sampler of known diameter and height was gently driven into the soil with the aid of a plank of wood and a mallet. To avoid compaction, another core sampler of similar size was placed on the one driven into the soil and hammered gently until one in the soil was completely buried. The first core sampler was dug out from the soil using an earth chisel making sure there was minimal disturbance to the sampler and its contents. Both ends of the sampler were trimmed with a knife and all 43 University of Ghana http://ugspace.ug.edu.gh extraneous materials were removed. Thereafter, the samplers were capped at both ends placed into labelled polythene bags and transported to the laboratory for bulk density determination in the laboratory. In the laboratory, the content of the sampler was emptied into a clean moisture can with known weight (W1). The moisture can together with its contents were oven dried at 105˚C until a constant weight (W2) was attained. Bulk density was calculated using the formula by Blake (1965). M ρb 3 = 2 [3.1] (Mg/m ) (πd ⁄4)h Where Ρb= Bulk density of soil M= mass of soil = W2-W1 W2 = Weight in grams taken after oven drying the moisture can and its contents. W1 = Weight in grams of empty moisture can. d = internal diameter of core h = height of core sampler (Π d2/4) h = volume of core = volume of soil 44 University of Ghana http://ugspace.ug.edu.gh Particle Size Analysis Bouyoucos hydrometer method modified by Day (1965) was used to determine the particles size distribution of the soil samples. Forty grammes (40 g) of the fine earth was weighed into a dispersing bottle. The soil was treated with H2O2 (1:1 soil: solution) to destroy the organic matter after which 100 mL of 5% calgon (sodium hexametaphosphate) solution was added to form a suspension. The suspension was shaken on a reciprocating mechanical shaker for 2 hours to help disperse the soil into the various separates (sand, silt and clay). The soil suspension was then transferred into a 1 L graduated sedimentation cylinder and topped up to the 1 L mark with distilled water. The suspension was thereafter agitated vigorously with a plunger and left to stand. After five minutes, a hydrometer was immersed and the first hydrometer reading taken. The first density reading was for both silt and clay in suspension. The second hydrometer reading (density of clay only in suspension) was recorded after 5 hours. The sand content was determined by pouring the suspension directly onto a 47 µm sieve. The contents on the sieve was washed thoroughly with tap water to get rid of any clay and silt particles and then transferred into a moisture can of known weight for oven drying at 105 0C for 24 hours. The hydrometer readings at five minutes and five hours were also taken in the blank which contains 5% calgon only. Temperatures of the suspensions at both hydrometer readings were recorded with the aid of a thermometer. Temperature effects on density of the soil particles were accounted for using the relation provided by Day (1965). For every 1°C increase in temperature, above 19.5 °C, there is an increase of 0.3 in the density of the particles in suspension. 45 University of Ghana http://ugspace.ug.edu.gh Correction for temperature = blank hydrometer reading – increase in weight of particles The concentration of the three separates were calculated as follows: (5 minute reading−correction for temperature ) % Clay and Silt = X 100 (3.2) oven dry mass of sample (8 hour reading−correction for temperature ) % Clay = X 100 (3.3) oven dry mass of sample % Silt = % (Clay and Silt) - % Clay (3.4) (oven dry weight of particles retained on the 47 μm sieve ) % Sand = X 100 (3.5) oven dry mass of sample The values for the soil separates were used to determine the textural class of the soils using the USDA textural triangle presented in Appendix. Moisture Content at Field Capacity One kilogramme of the bulk (un-sieved) soil was weighed into a pot with drainage holes which had been plugged with glass wool saturated with water. The saturated soil was covered with polythene to avoid evaporation and then allowed to drain for 48 hours in open air. Thereafter, sub samples of the soil were taken into moisture cans, weighed and oven dried at a temperature of 105 0C until constant weights were attained. The percentage water content at field capacity was then calculated as follows: weight of wet soil− weight of oven dried soil % water content = × 100 [3.6] Weight of the oven dried soil 46 University of Ghana http://ugspace.ug.edu.gh Soil Chemical Properties The sieved soil samples were subjected to various chemical analyses to determine properties including pH (in water and in salt), total and available phosphorus, total and available nitrogen, cation exchange capacity, and percent organic carbon. Soil pH Twenty grams of the fine earth fraction was weighed into a 50 mL beaker and 20 mL of deionized water added to give a 1:1 soil: water ratio. The suspension was stirred many times within 30 minutes and left to stand for about one hour. The glass pH meter was standardized using two buffer solutions of pH 4 and 7 and then the pH of the supernatant read. A pH was again determined in 0.01 M CaCl2 at a soil: salt ratio of 1:2. All the pH readings on the two soils were done in triplicates Total Carbon and Nitrogen Both soils were not likely to contain carbonates because they are highly weathered. The total carbon in the soils are, therefore, likely to be mainly of organic source. The total carbon and nitrogen content of the soils were determined using a Leco Trumac Carbon Nitrogen Sulphur version 1.3 Analyzer. Two hundred milligramme of the fine earth fraction of each soil was weighed into platinum crucibles mixed with 500 mg of comcat and placed in the furnace of the analyzer. The C and N concentrations in the samples were read after 6 minutes of combustion. Available Nitrogen Ten grammess of the fine earth of each of the soil was weighed into a 100 mL extraction bottle and 50 mL of 2 M KCl added. The soil suspension was shaken for 20 minutes in a reciprocating 47 University of Ghana http://ugspace.ug.edu.gh shaker. The suspension was then filtered through a No 42 Whatman filter paper into a clean empty plastic bottle. Ten millilitres aliquot of the filtrate was transferred into a 250 mL Kjeldahl flask and 0.2 g MgO powder was added to oxidise the NH +4 present to NH3 after which 100 mL of distilled water was added and distilled on a Markham distillation unit. Ammonia (NH3) was liberated into 5 mL of 2% boric acid (containing a methylene blue and methyl red indicator mixture) in a 150 mL conical flask. The solution left in the 250 mL Kjeldahl flask was allowed to cool and 0.2 g of Devarda’s alloy was added to reduce the NO3-N to NH + 4 -N. Nitrite in the sample was destroyed by the addition of 1 mL of sulphamic acid. Fifty millilitres of the distillate was collected into 5 mL of 2% boric acid indicator mixture in a separate conical flask. The distillates were then titrated against 0.01M HCl. The concentration of NO - 3 / NH + 4 mg L -1 soil was calculated as follows: + MHCl×VHCl×10 −3×18×V ×1000 mg NH KCl4g −1 = [3.7] (kg soil) Volume of Aliquot×Weight of soil (g) Where: MHCl = Molarity of the HCl VHCl = Titre of the HCl VKCl = Volume of KCl extractant 18 = Molecular weight of NH + 4 48 University of Ghana http://ugspace.ug.edu.gh Available Phosphorus Available phosphorus was determined using the method of Bray and Kurtz (1945). Five grammes of the fine earth of each soil sample was weighed into an extraction bottle. Fifty millilitres of Bray 1 solution (0.03M NH4F in 0.025M HCl) was added. The suspension was shaken for 3 minutes on a mechanical shaker after which it was allowed to settle. It was then filtered through a No. 42 Whatman filter paper into a 100 mL volumetric flask and made up to the volume. Phosphorus in the filtrate was determined using the molybdate-ascorbic acid colour development method of Murphy and Riley (1962) as follows: A five millilitre aliquot (in triplicates) of the supernatant was pipetted into a 100 mL volumetric flask and the pH adjusted with para-nitrophenol indicator. The solution was neutralized with a few drops of ammonium hydroxide (4M NH4OH) until the colour changed to yellow. This was followed by addition of distilled water till a colourless solution was observed. Reagent A was prepared by dissolving 12 g of ammonium molybdate and 0.2998 g of antimony potassium tartrate in 250 mL of distilled water. Reagent B was prepared by dissolving 1.056 g of ascorbic acid in 200 mL of Reagent A. The dissolved reagents were added to 1000 mL of 2.5 M H2SO4, mixed thoroughly and made to volume in a 2000 mL volumetric flask. Eight millilitres of Reagent B was then added to the sample solution and made to volume in a 100 mL volumetric flask. A blank was also prepared using 5 mL of distilled water and 8 mL of reagent B. A Philips PU 8620 spectrophotometer was calibrated using six P standard solutions including a blank which was the Bray background solution and the reagents A and B. Phosphorus in the solution was determined by reading the resultant colour intensity on the Philips PU 8620 49 University of Ghana http://ugspace.ug.edu.gh spectrophotometer, at a wavelength of 712 nm. The available P concentration in the soil sample was read and calculated using the spectrophotometer reading as follows spectrophotometer reading (𝑚𝑔𝐿−1)× total volume of extract P (mg/kg) = × 100 [3.8] volume of aliquot × weight of soil sample × 106 Total Phosphorus Total phosphorus was determined by digesting 2 g of 0.5 mm sieved soil with 25 mL of a mixture of concentrated HNO3 and 60% HClO4 in a ratio of 2:3 (HNO3 : HClO4). The digestion was continued until white fumes of HClO -4 ceased. The digest was cooled, diluted with distilled water and then filtered into a 100 mL volumetric flask using a No. 42 Whatman filter paper. The volume was brought to the 100 mL mark with distilled water. Phosphorus in the filtrate was measured by colour development and read on Philips PU 8620 spectrophotometer as described in section 3.2.2.4 and the calculation for percent P in soil sample was calculated using equation [3.8]. Exchangeable Bases and Cation Exchange Capacity (CEC) Extraction of Exchangeable Bases. Five grammes (5 g) of the fine earth fraction was weighed into a 200 mL extraction bottles. Fifty (50) mL of 1 M ammonium acetate (NH4OAc) solution buffered at pH 7.0 was added. The bottles were covered and shaken on a reciprocating shaker for 1 hr. The soil suspension was then filtered through a No. 42 Whatman filter paper. The filtrates were used for the determination of Ca, Mg, K and Na. The concentrations of the basic cations in the filtrate were read on an atomic absorption spectrometer (AAS) (A Analyst 800). The AAS was calibrated with the appropriate standards for Ca, Mg, K and Na, respectively and the absorbance for each element determined. Exchangeable bases were calculated as follows: 50 University of Ghana http://ugspace.ug.edu.gh −1 R × Vol.of extract ×10 3 (g) × 102(cmol)×E X (cmolckg ) = [3.9] Weight of soil ×106 (µg)× M Where X = Basic cation R = AAS (Atomic absorption spectroscopy) reading in mg L-1 E = Charge of basic cation M = Atomic mass of basic cation Cation Exchange Capacity (CEC) The residue after filtration in section 3.2.2.6.1 was immediately leached with four portions of 50 mL methanol (to get rid of excess ammonium) into empty plastic bottles. The soil was leached again with four 50 mL portions of acidified 1 M KCl. Each portion was added at a time and allowed to pass through, before adding the next portion. Five millilitres of the leachate was transferred into a Kjeldahl flask and 5 mL of 40% NaOH added and then distilled into 5 mL of 2% boric acid. This was then back titrated against 0.01M HCl. The ammonium ion concentration in the filtrate in cmol kg-1c soil was determined as the CEC of the soil. Exchangeable Acidity (H+ and Al3+). Five (5) grammes of soil was weighed into a 100 mL extraction bottle and 50 mL of 1 M KCl solution was added. The bottle and its content were placed on a mechanical shaker and shaken for 1 hour. The soil suspension was then centrifuged and the supernatant decanted into an empty clean bottle. Twenty millilitres aliquot was pipetted into a 100 mL conical flask, heated to near boiling point to drive out CO2, allowed to cool down and 2-3 drops of phenolphthalein indicator added for 51 University of Ghana http://ugspace.ug.edu.gh titration to a permanent pink end point against 0.01 M NaOH. The titre value was recorded as titre for both H+ and Al3+. Five millilitres of 4% NaF was added to the solution at the endpoint and back titrated against 0.01M HCl until a colourless end point was reached. The titre was recorded as that for Al3+. (𝑚𝐿 𝑁𝑎𝑂𝐻 𝑠𝑎𝑚𝑝𝑙𝑒−𝑚𝐿 𝑁𝑎𝑂𝐻 𝑏𝑙𝑎𝑛𝑘) ×𝑁 ×100 cmolc/kg KCl acidity = [3.10] 𝑠𝑎𝑚𝑝𝑙𝑒,𝑔 𝑚𝐿 𝐻𝐶𝑙 ×𝑁×100 cmolc/kg KCl exchangeable Al = [3.11] 𝑠𝑎𝑚𝑝𝑙𝑒,𝑔 cmolc/kg H = KCl exchangeable acidity – KCl exchangeable Al [3.12] Effective Cation Exchange Capacity (ECEC) The Effective Cation Exchange Capacity (ECEC) of the two soils were estimated as the sum of the exchangeable Ca2+, Mg2+, Na+, K+, H+, and Al3+. (i.e. Ca2++ Mg2++ Na++ K++ H++Al3+) Preparation of Biochar Biochar from the feedstock of corn cob and rice straw were used as liming material in this study. Both the rice straw and the corn cob biochar were carbonized in a furnace at pyrolysis temperatures of 500 ºC and 700 ºC at the Soil Research Institute of the Council for Scientific and Industrial Research, Kwadaso, Kumasi. The charred rice straw and the corn cob were washed with deionized water and air dried, and then ground. The ground biochar was then passed through a 2 mm sieve and saved for chemical characterization which included pH both in water and salt, total and available P, total N, organic carbon, and soluble K, Mg, Ca and Na. 52 University of Ghana http://ugspace.ug.edu.gh Biochar pH One gramme of each of the ground biochar types was weighed into a beaker and 10 mL of de- ionised water added to give biochar water ratio of 1:10. This ratio was used to ensure enough volume of supernatant for immersion of electrode. The mixture was then stirred several times for about 30 minutes and left to stand for about an hour to allow most of the suspension to settle and also for the suspension temperature to equilibrate with the temperature in the instrument room. The glass electrode pH meter- CG818, Schott Great was standardized using two solutions of pH 7 and 9. The electrode was then rinsed with distilled water and then immersed into the partly settled suspension and the reading on the pH meter recorded. The determination of pH of the sample was repeated using 0.01 M CaCl2 solution according to the protocol outlined earlier for reading pH of biochar in water. Biochar Available Phosphorus Available phosphorus was determined by the Olsen method (1965). One gramme of biochar sample was weighed into an extraction bottle and 50 mL of 0.5 M NaHCO3 solution was added and shaken for 30 minutes on a mechanical shaker. The biochar extractant mixture was filtered through a Whatman No. 42 filter paper. A 10 mL aliquot was taken and 10 mL sulphuric acid (H2SO4) added and centrifuged at 3000 rpm for 15 minutes. The concentration of the P in each sample was then determined after colour development using the Murphy and Riley (1962) method as described in section 3.2.2.4 The intensity of the colour developed at a wavelength of 712 nm was read on the UV spectrophotometer and recorded. The P was calculated using the formula in [3.8]. 53 University of Ghana http://ugspace.ug.edu.gh Exchangeable Cations in Biochar Two grammes of biochar was weighed into an extraction bottle and 50 mL of 1 M ammonium acetate (NH4OAc, pH 7) was added. The bottle was shaken on a mechanical shaker for one hour and the contents filtered through a Whatman No. 42 filter paper into clean empty bottles. Addition of the ammonium acetate extracted the soluble basic cations in the ash of the biochar and the cations at the exchange site of the material. The concentration of both soluble and exchangeable calcium, sodium, potassium and magnesium in the extract were determined using the Atomic Absorption Spectrophotometer (AAS) and calculated as in equation [3.9]. Soluble Cations in Biochar Two grammes of biochar was weighed into an extraction bottle and 50 mL of de-ionised water was added. The suspension in the bottle was shaken on a mechanical shaker for an hour and the contents filtered through a Whatman No. 42 filter paper into clean empty bottles. Addition of water extracted the water soluble basic cations in the ash of the biochar. The concentration of water soluble calcium, sodium, potassium and magnesium in the extract were determined using the Atomic Absorption Spectrophotometer (AAS) and calculated as in equation [3.9]. Incubation Study Cylindrical PVC pipes of 20 cm internal diameter were cut into of 20 cm lengths. One end of the 20 cm pipes was covered with a wire mesh tired to the pipes and also held in place by metal clips to form pots of height 20 cm and internal diameter 20 cm. Preliminary studies using the rice husk and corn cob biochar types prepared at both 500 oC and 700 oC have revealed that application rates between 60 and 80 tonnes/ha to a typical acid soil was able to raise the pH by 2 pH units. An 54 University of Ghana http://ugspace.ug.edu.gh incubation study using samples of the two soils, the four biochar types and a conventional liming material, laboratory grade (Analar) CaCO3 of 99% purity as control was undertaken to establish the efficacy of the biochar types as liming materials, and if efficacious ascertain the equilibration time i.e. how long a farmer has to wait upon amendment of the soils with biochar before sowing or planting. The unprocessed bulk soils of the Ankasa and Tikobo Series were mixed with each of the four biochar types i.e. rice husk and corn cob biochar types prepared at both 500 oC and 700 oC at 80 tonnes/ha to attain their respective bulk densities. Equivalent amounts of Ca in the biochar from CaCO3 was added to the soil as conventional agricultural lime. In estimating the amount of CaCO3 to be added, the Ca equivalent in the biochar with the highest exchangeable and soluble Ca was used. A treatment with no amendment was also included. The moisture contents of the soils in pots were kept at 80% field capacity in the screen house. All the treatments were replicated four times and arranged in completely randomized design. Average temperature during the period of incubation was between 27 oC and 32 oC. The pH of the soils was read at 7 days interval till there was no apparent change in soil pH (equilibration). Available bases, available phosphorus, exchangeable H+ and Al3+ were read once every 14 days during the equilibration period. The experimental set up for the incubation study is shown in plate 1. Evaluation of Effect of Liming on Growth Characteristics of Soya bean Upon equilibration of the soils amended with the five liming materials viz. rice husk and corn cob biochar at 500 oC and 700 oC and the conventional liming material, an agronomy study using the 55 University of Ghana http://ugspace.ug.edu.gh limed soil and soya bean (Glycine max) of variety Jankuma as a test crop was carried out in the screen house to investigate the effect of liming on growth characteristics of soya bean. Soya bean was the preferred crop because it is sensitive to pH. The soya bean seeds of 80% germination were inoculated with Histick Soy, a commercial inoculant from BASF chemical company in Germany and sown at stake at four seeds per pot Plate 1 Experimental set up of the incubation study in the screen house 56 University of Ghana http://ugspace.ug.edu.gh and were later thinned to one seedling per pot. The levels of available P in the four biochar types added as lime were similar and were therefore averaged and the equivalent from TSP added as a P source to half the number of pots receiving CaCO3 as a liming material. To ascertain the efficacy of the available P from the biochar, the nutrient from two sources i.e. biochar and TSP were compared on the limed soils. Triple super phosphate (TSP) as synthetic source of P and urea as synthetic source of N were applied at a rate of 30 kg P ha-1of P and 10 kg N/ha, respectively to half the number of limed soils to evaluate the effect of synthetic P and N on growth characteristics of soya bean and also on P availability. The inorganic fertilization was done two weeks (2) after germination. Thus, with two soils, five liming amendments, two synthetic P and N rates i.e 0 P and N ha-1, 10kg N ha-1 and 30 kg P ha-1 and four replicates. There were 2 soil x 5 amendments x 2 P Rates x 2 N rates factorial experiment which were replicated four times in a completely randomized design as explained in the incubation study. In addition to these, there were four un- amended soils each for the two soils. The moisture contents of the soils were maintained at 80% throughout the experiment. The experimental set up showing the plants growing in the screen house is shown in Plate 2. At flower initiation, six weeks after sowing which is the critical stage for nodulation, the soya bean plants were harvested. The whole plant with soil were gently put into a big basin and soil carefully separated from the roots. 57 University of Ghana http://ugspace.ug.edu.gh Plate 2 Pot experiment showing soya bean plants in the screen house. 58 University of Ghana http://ugspace.ug.edu.gh Crop Parameters Determined The plants in the pots were harvested by cutting off the shoot at the surface of soil in the pots. The shoots were then kept in envelopes and dried to a constant weight at 65 0C in an oven to determine the shoot dry weight. Part of the oven dried shoot was milled for total P determination. The below soil plant biomass was uprooted making sure the roots and the nodules were intact. The soil adhering to the roots were then carefully washed off in a bowl of water. The nodules were then detached from the roots and counted into envelopes. The nodules were dried to a constant weight at 65 0C for in oven to determine the nodule dry weight. The respective volumes of the washed roots from individual pots were measured by using the water displacement method. A known volume of water was poured into measuring cylinder and individual roots per pot were immersed gently into the water with the aid of forceps. The changes in water levels were recorded and used as the volume of the roots. The water in the measuring cylinder was changed after each measurement to enable the roots displace their actual volume and also to ensure accurate reading. The roots were then transferred into separate envelopes and dried to a constant weight at 65 0C in oven to determine the root dry weight. Part of the oven dried roots was milled for total P determination. Total P of Plant Material Hundred milligrammes of each of the milled shoot and root samples were weighed into 50 mL conical flask and 5 mL of concentrated sulphuric acid (H2SO4) was added. The flask was then swirled to ensure that the acid mixed thoroughly with the milled sample and left to stand overnight. This allowed for a thorough dissolution of the samples by the acid. The flask and its content were 59 University of Ghana http://ugspace.ug.edu.gh then heated on a sand bath for 1 min and H2O2 was added drop wise with intermittent swirling till the solution was clear. Deionized water was added to the solution and left to cool, after which the solution was filtered through a No. 42 Whatman filter paper into a 100 mL volumetric flask and made to the mark with deionized water. A 5 mL aliquot of the digest was pipetted into 50 mL volumetric flask in duplicates and colour developed according to the method of Murphy and Riley (1962) as outlined in section 3.2.2.4. The shoot and root total P were determined as P% content as: shoot % P Total P (mg/pot) = shoot dry weight (g⁄pot) × × 1000 [3.15] 100 Residual Analyses The soil samples after harvesting were homogenized, subsampled, air dried, sieved through a 2 mm sieve, labelled and used in the determination of residual pH, total and available P. Soil Residual pH Twenty grammes (20 g) of the soil sample was weighed in triplicates into 50 mL beakers, 20 mL of distilled water was added to the samples and stirred continuously for 30 min. The soil suspension was then left to stand for an hour. The glass electrode pH meter was standardized and the pH measured as described in section 3.2.2.1. Soil Residual Available Phosphorus The available and total P levels in the processed soils after harvesting were determined according to their respective methods outlined in sections 3.2.2.4 and 3.2.2.5. 60 University of Ghana http://ugspace.ug.edu.gh Soil Residual Total Nitrogen and Carbon The soil residual total nitrogen and carbon were determined by using the Nitrogen and Carbon Analyzers, as outlined in section 3.2.2. 2. Data Analyses The measured crop parameters, nutrient uptake and the residual soil analyses after harvest were subjected to analysis of variance (ANOVA) using Genstat 12th edition to establish if there were any significant treatment effects at p˂ 0.05. mean separations were done using Lsd (0.05). 61 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR 4 RESULTS Characterization of Soils. Some physico-chemical properties of the plough layer (0 -20 cm) of the two soils used for the study are presented in Table 4.1. The Acrudox, Ankasa Series has a sand content of 61.5% which is 20.4% lower than that of the Hapludult, Tikobo Series. The Acrudox again has a lower silt content of 7.8% compared to the 12.5% of the Hapludult. Clay concentration was, however, almost six times higher in the Acrudox (30.7%) than in the Hapludult (5.6%). The bulk density of the Ankasa Series, 1.1, Mg/m3, was lower than the 1.3 Mg/m3 of the Tikobo Series. Ankasa Series is extremely acid with pH in salt and water being 3.7 and 4.2, respectively. Tikobo Series on the other hand is very strongly acid with a pH of 4.9 in water and 4.0 in salt at the depth of 0-20 cm. The organic carbon content of Ankasa which is from a forest reserve is 15.3 g/kg and that of Tikobo sampled from a fifteen a year fallow area is 5.4 g/kg. Despite the almost 2.8 times more C in the Ankasa Series than the Tikobo Series, total N in the former (1.6 g/kg) was similar to that for Tikobo Series (1.2 g/kg). Consequently, the available N concentration of Ankasa Series, 0.42 g/kg is close to that of Tikobo, 0.31 g/kg. The Acrudox has a total P concentration of 164 mg/kg which is 63 mg/kg more than the 101.4 mg/kg of Hapludult. The two soils have very low available P concentrations of 1.54 mg/kg and 2.71 mg/kg for the Acrudox and Hapludult, respectively. 62 University of Ghana http://ugspace.ug.edu.gh Table 4. 1: Some Physical and Chemical Properties of the Soils Used ---------SOIL TYPE-------------- PARAMETERS ANKASA TIKOBO Soil pHwater 4.2 4.9 Soil pHSalt 3.7 4.0 Sand (%) 61.5 81.9 Clay (%) 30.7 5.6 Silt (%) 7.8 12.5 Textural class sandy clay loam loamy sand OC (g/kg) 15.3 5.4 Total N (g/kg) 1.60 1.2 Available N (g/kg) 0.42 0.31 Total P (mg/kg) 164.0 101.4 Available P (mg/kg) 1.54 2.71 Ca (cmolc/kg) 0.64 0.70 Mg (cmolc/kg) 0.05 0.07 K (cmolc/kg) 0.08 0.06 Na (cmolc/kg) 0.06 0.06 Al (cmolc/kg) 1.31 0.40 H (cmolc/kg) 0.29 0.34 CEC (cmolc/kg) 17.8 8.9 ECEC (cmolc/kg) 2.63 1.73 Al Saturation (%) 54.80 24.54 63 University of Ghana http://ugspace.ug.edu.gh The Ankasa Series being an Oxisol has a higher exchangeable acidity (exchangeable Al3+ + H+) of 1.60 cmolc/kg which is more than twice the value, (0.74 cmolc/kg) for the Ultisol. It is worthy of note that even though the two soils have similar exchangeable H+ values i.e. 0.29 and 0.34 cmolc/kg, the exchangeable Al 3+ in the Ankasa Series is thrice more than that of the Tikobo Series (0.40 cmolc/kg). Relatively, the exchangeable bases of the two soils were very low between 0.83 and 0.9 cmolc/kg. It is also worthy of note that the CEC of the soils are far higher than their respective ECECs and the CEC of Ankasa Series is twice more than that of the Tikobo Series. The CEC and ECEC are 17.8 cmolc/kg and 2.68, respectively for the Ankasa Series and 8.9 cmolc/kg and 1.73 cmolc/kg for Tikobo Series. Aluminium saturation which was calculated as a percentage of the ECEC was 54.8% for Ankasa Series and 24.5% for Tikobo Series. Chemical Characterisation of Biochar The chemical properties of the two un-charred feed stock i.e. rice husk (RH) and corn cob (CC) and their respective biochar derivatives charred at 500 0C and 700 0C herein after referred to as RH 500, RH 700, are rice husk charred at 500 0C and 700 0C and CC 500 and CC700 are corn cob charred at 500 0C and 700 0C are presented in Tables 4.2 and 4.3. The pH in water of the un- charred feed stocks are generally neutral in reaction with the pH of rice husk and corn cob in water being 6.1 and 6.8, respectively. Upon charring however, pH in water of RH500 biochar increased by 1.5 pH units to 7.6 becoming slightly alkaline whilst its RH700 counterpart became alkaline by increasing to 8.8. The CC biochar types became strongly alkaline after charring with pH of CC500 in water being 10.7 and 11.0 for CC700. 64 University of Ghana http://ugspace.ug.edu.gh Table 4. 2: Chemical Properties of Feedstock and Biochar Types Used* Feedstock Pyrolysis ----------pH---------- Temp oC 1:1(H2O) 1:1(KCl) Total C Total N C: N Total P Av. P ------------ g/kg---------- ---------- mg/kg-------------- CC --- 6.8 -- 402.6 9.7 41.5 1408.1 -- RH -- 6.1 -- 353.1 7.6 46.5 1543.9 -- CC 500 10.7 10.8 567.9 0.82 692.6 4950.1 2162.5 CC 700 11.0 11.4 602.9 0.78 772.9 5910.2 2287.5 RH 500 7.6 7.9 387.1 0.55 703.8 5870.0 2378.8 RH 700 8.8 9.1 389.0 0.51 762.7 6020.5 2290.1 *CC = corn cob, RH = rice husk 65 University of Ghana http://ugspace.ug.edu.gh Table 4. 3: Total, Exchangeable and Soluble Bases of Feedstock and Biochar Types Used* Feedstock pyrolysis Total bases Exchangeable base Soluble bases Temp oC Ca Mg K Na Ca Mg K Na Ca Mg K Na --------------------------------------------------- % ------------------------------------------------------------------ CC - 0.32 0.05 0.24 0.32 - - - - - - - - RH - 0.36 0.07 0.19 0.28 - - - - - - - - CC 500 0.71 0.15 1.87 1.25 0.15 0.05 0.21 0.08 0.02 0.01 0.01 0.01 CC 700 0.92 0.18 1.93 0.91 0.18 0.05 0.22 0.07 0.07 0.02 0.01 0.01 RH 500 1.07 0.17 0.68 0.93 0.16 0.03 0.06 0.04 0.02 0.01 0.01 0.01 RH 700 1.21 0.16 0.81 0.96 0.16 0.04 0.06 0.07 0.02 0.01 0.01 0.01 *CC = corn cob, RH= rice husk, 66 University of Ghana http://ugspace.ug.edu.gh The slightly alkaline to strongly alkaline pH of the biochar types agrees with Verheijen et al. (2010) who reported that anaerobic charring of feedstock leads to biochar with pH between neutral and strongly alkaline. The pH in the salt (KCl) was similar to that of in water as change was not more than 0.5 pH units (Nartey, 2000). Total organic carbon of the CC feedstock was 402.6 g.kg; 49.5 g/kg more than that in the RH feedstock (Table 4.2). There were marginal increases in carbon content on charring of the RH feedstock at the two temperatures as carbon concentration in RH500 increased to 387.1 with its RH700 counterpart attaining a value of 389.0 g/kg. There were, however, approximately 41% and 50% respective increases in C concentrations when the CC was charred at 500 oC and 700 oC. Total nitrogen (TN) contents of the CC and RH were 9.7 and 7.6 g/kg (Table 4.2), respectively. On charring, TN decreased from 9.7 to 0.82 and 0.79 in the CC500 and CC700 biochar types respectively. Losses of the volatile element, N, was higher in the rice husk biochar types as TN concentration was 13.8 (RH500) and almost 15 (RH700) times lower than in the original feedstock from which they were derived Unlike total C and N which were higher in the CC feedstock than its rice husk counterpart, total P in the two feed stocks was close with concentrations of 1408.2 mg/kg (0.14%) for CC and 1543.9 (0.15%) for RH. Available phosphorus concentrations, just as in the total P was close in the four biochar derivatives with values between 2162.5 mg/kg and 2378.5 mg/kg. The concentration of total bases in the CC was 0.93% whilst the RH was 0.90% (Table 4.3). On charring, the sum of total bases in the four biochar types was in the order of CC 700 (3.94%) ≈ CC500 3.98%) > RH700 (3.14%) > RH500 (2.85%). Just as was found for the bases in the 67 University of Ghana http://ugspace.ug.edu.gh respective feedstocks from which the biochar types were derived, total Na and K was higher in the CC biochar types than RH biochar types whereas total Ca and Mg were higher in the RH biochar typesthan CC biochar types. Order of concentrations of the sum of exchangeable bases in the four biochar types was CC 700 (0.52%) ≈ CC500 0.49%) > RH700 (0.33%) ≈ RH500 (0.31%). It is worthy of note that exchangeable K is strikingly higher in the two CC biochar types than their RH. Effect of Amendments on Soil pH The changes in soil pH upon amendment of Ankasa Series with the four biochar types and the conventional agricultural lime (CaCO3) are presented in Figure 1. The pH in water of the un- amended Ankasa Series, the Acrudox, increased from its inherent 4.2 to 4.7 when the soil was amended with the conventional liming material (CaCO3) at the Ca equivalent in the biochar i.e. 104 kg Ca/ha or 260 kg CaCO3/ha after one week of incubation in the screen house. Thereafter, there was marginal change in pH with time for the ensuing five weeks. When the four biochar types were applied at the similar Ca rate as the conventional liming material, pH increased by 0.5, 0.6 0.65 and 0.7 pH units to 4.7, 4.8, 4.85 and 4.9, respectively for CC700, RH700, CC500 and RH500 after one week of incubation. From the second week of incubation, the CC700 amended soil gave the highest increase in pH rising from 4.9 to about 5.1 at the end of the sixth week. The other biochar amended soils were similar in pH values from the second week with values between 4.7 and 4.8 and rising marginally to between 4.9 and 5.0 at the end of the sixth week. The changes in pH on amendment of Tikobo Series, is presented in Figure 2. The Tikobo Series, an Ultisol had an initial pH of 4.9 which rose to about 5.3 after one week of incubation when the conventional liming material, CaCO3 was applied at 260 kg/ha. Within that same one week 68 University of Ghana http://ugspace.ug.edu.gh 6.5 CC700 CC500 RH700 RH500 CaCO3 6 5.5 5 4.5 4 0 1 2 3 4 5 6 Time (Week) Figure 1. Changes in pH upon addition of amendments in Ankasa Series 6.5 6 5.5 5 4.5 4 0 1 2 3 4 5 6 Time (Week) Figure 2. Changes in pH upon addition of amendments in Tikobo Series 69 PH PH University of Ghana http://ugspace.ug.edu.gh period of incubation, pH in water rose to 5.2, 5.5, 5.6 and 5.9, respectively when the soil was amended with RH700, RH500, CC700 and CC500. Thereafter the CC500 and CC700 increased the soil pH to 6.2 and 6.0, respectively by the end of the sixth week. Effect of Amendments on Changes in Concentration of Exchangeable Al and Ca in the Soil The changes in concentrations of Al and Ca in Ankasa Series are shown in Figure 3. The broken lines represent Al concentrations whilst the full lines represent concentrations of Ca. The concentration of Al in the Ankasa Series when amended with the five liming materials generally started decreasing from week four except for the CC700 and RH700 where the decreases started from week two. Generally, Ca concentrations in soil solution started increasing from week two rising steadily to a maximum in week six for all the amended soils except the CC500 amended soil where rise in Ca concentration was observed from week four. By the end of the sixth week Ca concentration was least in the CaCO3 amended soils with a corresponding highest value in Al concentration in soil solution. The RH biochar amended soils had the highest Ca concentrations in soil solution with values between 2.0 and 2.5 cmolc/kg. Co-incidentally their Al concentration in the amended soils was among the lowest with values between 0.52 and 0.6 cmolc/kg. From Figure 3, it is clear that Al concentrations after amendment of Ankasa Series with the liming materials Ca application rate of 104 kg/ha did not reduce Al to the barest minimum as concentrations after six weeks were above 0.5 cmolc/kg in soil solution. Corn cob biochar charred at 700 oC reduced Al concentration to 0.44 cmolc/kg from 1.31 cmolc/kg during incubation whilst it increased Ca concentration from 0.64 cmolc/kg to 1.12 during the six weeks of incubation in Ankasa Series. CaCO3 decreased Al concentration from 1.31 cmolc/kg to 0.70 cmolc/kg and also 70 University of Ghana http://ugspace.ug.edu.gh Ca CC 700 Al CC 700 Ca CC 500 Al CC 500 2.5 Ca RH 700 Al RH 700 Ca RH 500 Al RH 500 2 Ca CaCO3 Al CaCO3 1.5 1 0.5 0 0 2 4 6 Time (Weeks) Figure 3. Changes in Exchangeable Al and Ca concentration upon addition of amendments to Ankasa Series. 71 Exchangeable Ca & Al (cmolc/kg University of Ghana http://ugspace.ug.edu.gh increased Ca concentration from 0.64 cmolc/kg to 0.89 cmolc/kg in Ankasa Series. Rice husk biochar was able to increase Ca concentration to 2.20 cmolc/kg during the incubation period. In the Tikobo Series decreases in Al concentrations with corresponding increases in Ca concentration were observed from the second week of amending the soil with the five liming materials (Figure 4). It is noteworthy that by the end of the six weeks incubation period, even though the conventional lime amended soil had a very high Ca concentration in solution (1.8 cmolc/kg), it was the only amended soil that still had Al in soil solution albeit low level (0.08 cmolc/kg; all other amended soils had non-detectable levels of Al. The CaCO3 was able to increase Ca concentration from 0.70 cmolc/kg to 1.58 cmolc/kg during the incubation period in Tikobo Series. Corn cob biochar at 700 0C also increased Ca concentration to 1.15 cmolc/kg. Effects of Amendment on Mg2+, K+, Na+ and H+ Concentrations in the Soil. The concentrations of Mg2+, K+, Na+ and H+ in soil solution upon amendment of the two soils with the five liming materials are presented in figures 5 to 12. Generally, Mg, K, and Na increased in both soils whilst concentration of H decreased during the incubation period. It is clear from the figures, that is was only the basic cation Mg that started increasing in solution from the onset of incubation, i.e first week of incubation (Figure 5). The other two basic cations, K and Na generally increased in soil solution from week two. Generally, the concentrations of Mg, K and Na in the biochar amended soils were higher than in CaCO3 amended soil. Though the CaCO3 did not contain Mg and Na as active ingredients, it is clear from Figures 5 and 6 that addition of the conventional liming material to the Ankasa Series increased Mg from 0.05 cmolc/kg in the un- amended Ankasa soil to 0.3 cmolc/kg. Sodium concentration also increased from 0.06 cmolc/kg to 0.82 72 University of Ghana http://ugspace.ug.edu.gh 2.5 2 1.5 1 0.5 0 0 2 4 6 Time (weeks) Figure 4. Changes in Exchangeable Al and Ca concentration upon addition of amendments to Tikobo Series. AC 700 AC 500 AR 700 AR 500 CaCO3 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 2 Time (week) 4 6 Figure 5. Changes in Mg concentration upon addition of amendments to Ankasa Series 73 Available Mg (cmolc/kg) Exchangeable Ca & Al (cmolc/kg) University of Ghana http://ugspace.ug.edu.gh 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 5 6 Time (Week) Figure 6. Changes in Mg concentration upon addition of amendments to Tikobo Series 74 Available Mg (cmolc/kg) University of Ghana http://ugspace.ug.edu.gh cmolc/kg. Increase of Mg in the Tikobo Series was, however, marginal ranging from 0.07 cmolc/kg to about 0.15 cmolc/kg. Sodium availability in Tikobo increased from 0.06 to 0.73 cmolc/kg at the end of the six weeks incubation period. Availability of the basic cations, Mg, K and Na increased greatly when the two acid soils were amended with the four biochar types with level of increases being in the order of Na > K > Mg. Available Na in the Ankasa soil amended with the four biochar types was between 1.6 and 1.9 cmolc/kg while available K was between 0.6 and 1.2 cmolc/kg. Magnessium was least with availability being between 0.5 and 0.6 cmolc/kg within the six weeks of incubation. In Tikobo Series, availability of Na was between 0.9 cmolc/kg and 2.5 cmolc/kg; K between 0.7 and 1.2 cmolc/kg and Mg between 0.4 and 0.6 cmolc/kg. Availability of K was especially higher in the CC biochar types after two weeks of amendment than in the RH types when applied to Tikobo Series The acidic cation, H+ on the other hand generally decreased in solution from the onset of incubation (Fig. 11 and 12). The concentration of H+ in solution at the end of the six week incubation period was highest in the CaCO3 amended soils and higher in the Acrudox (0.28 cmolc/kg) compared to the Hapludult (0.21 cmolc/kg) Changes in Available P with Liming The changes in available P concentration with time in Ankasa Series after amendment with the five liming materials are presented in Figure 13. Two weeks of amendment with CaCO3 increased available P concentration from 1.54 mg/kg to about 5 mg/kg and to about 12.65 mg/kg by the sixth week. The biochar amended Ankasa Series increased in available P content to between 12 and 18 75 University of Ghana http://ugspace.ug.edu.gh mg/kg by the end of the second week. The CC biochar types recorded the highest available P concentration of between 15 and 18 mg/kg. By the end of the sixth week, available P was highest in the RH biochar amended soils with concentration of 30.10 mg/kg. The CC500 biochar amended soil recorded available P concentration of 25 mg/kg with its CC700 amended soil having a concentration of about 15 mg/kg On amendment of CaCO3 to the Tikobo soil, there was marginal change in P concentration till after four weeks when increase in P availability was steep rising from about 3 mg/kg to about 12 mg/kg (Fig. 14). Amending Tikobo Series with the four biochar types increased P availability steadily with time (Fig. 14). By the end of the sixth week of incubation, availability of P in Tikobo had increased from a paltry 2.71 mg/kg to between 22 mg/kg and 30.10 mg/kg. Rice husk biochar at 500 oC improved Tikobo P status from 2.71 to 30.10 mg/kg with the corn cob biochar at the same temperature increasing the P level of Tikobo Series to 27.79 mg/kg at the end of the incubation period. It is worthy of note that in both Ankasa and Tikobo Series amended with CaCO3, sharp increases in P availability coincided with decreases in Al solubility around the fourth week. Effect of Liming Amendments on Growth Parameters of Soya bean Liming controls pH which in turn controls P availability in soils (Brady and Weil, 2002). Phosphorus is one of the main nutrients that controls root development and expansion in plants and hence nutrient absorption by plants (Marschner, 1998). Root volume, mass and shoot dry weight of the test crop soya bean, were, therefore used as indices for effect of liming in the two soils. 76 University of Ghana http://ugspace.ug.edu.gh CC 700 CC 500 RH 700 RH 500 CaCO3 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5 6 Figure 7. Changes in K concentration upon addition of amendments to Ankasa Series 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5 6 Time (Week) Figure 8. Changes in K concentration upon addition of amendments to Tikobo Series 77 Available K (cmolc/kg University of Ghana http://ugspace.ug.edu.gh CC 700 CC 500 RH 700 RH 500 CaCO3 2.5 2 1.5 1 0.5 0 0 1 2 3 4 5 6 Time (Week) Figure 9. Changes in Na concentration upon addition of amendments to Ankasa Series 3 2.5 2 1.5 1 0.5 0 0 1 2 3 4 5 6 7 Time (Week) Figure 10. Changes in Na concentration upon addition of amendments to Tikobo Series 78 Available Na (cmolc/kg) Available Na(cmolc/kg University of Ghana http://ugspace.ug.edu.gh 0.35 TCC 500 TCC700 TRH 500 TRH700 CaCO3 0.3 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 6 Time (Week) Figure 11 Changes in H concentration upon addition of amendments to Ankasa Series 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 6 Time (week) Figure 12. Changes in H concentration upon addition of amendments to Tikobo Series 79 Available H (cmolc/kg Available H (cmolc/kg) University of Ghana http://ugspace.ug.edu.gh CC 700 CC 500 RH 700 RH 500 CaCO3 35 30 25 20 15 10 5 0 0 1 2 3 4 5 6 7 Time (Week) Figure 13. Changes in P concentration after addition of amendments to Ankasa Series 80 Available P (mg/kg) University of Ghana http://ugspace.ug.edu.gh CC 500 CC 700 RH 500 RH 700 CaCO3 35 30 25 20 15 10 5 0 0 1 2 3 4 5 6 Time (Weeks) Figure 14. Changes in P concentration after addition of amendments to Tikobo Series 81 Available P (mg/kg) University of Ghana http://ugspace.ug.edu.gh Effect of Liming on Root Volume The effect of liming on root volume of soya bean plants in the Ankasa Series is presented Table 4.4. From the table, it is seen that root volume of the soya bean plants in the un-amended was very small averaging 1.2 cm3. On amending the soil with CaCO3, the root volume increased 2.7 times to 3.25. Application of the four biochar types also gave significant (p< 0.05) increases in root volumes over that of the un-amended. The CC500 biochar type had the least effect on root expansion with volume increasing by 1.8 times over that of the un-amended soils compared to between 2.6 and 2.8 times when the other three biochar types were applied. The other three biochar types i.e. CC700, RH500 and RH700 did not differ significantly (p>0.05) among themselves with respect to effect on root expansion of soya bean when amended to Ankasa Series. The root volume in un-amended Tikobo Series was 1.45 cm3. On liming with the conventional liming material, the root increased significantly (p<0.05) in volume to 3.33 cm3 (Table 4.4). Liming with the four biochar types also increased root volume significantly (p<0.05) to between 3.89 cm3 and 5.99 cm3; The effect of biochar liming on root expansion in the Tikobo Series was in the order RH500 > CC700 > CC500>RH700. All the biochar types except RH700 were superior to the conventional liming material on the effect on root expansion. The roots of soya bean plants after harvesting are shown in plates 3 and 4. 82 University of Ghana http://ugspace.ug.edu.gh Root in Un-amended soil Root in CaCO3 amended soil Root in CC biochar amended soil Root in RH biochar amended soil Plate 3. Soya bean Root in Ankasa Series 83 University of Ghana http://ugspace.ug.edu.gh Root in un-amended soil Root in CaCO3 amended soil Root in CC biochar amended soil Root in RH biochar amended soil Plate 4. Soya bean Root in Tikobo Series 84 University of Ghana http://ugspace.ug.edu.gh Table 4. 4: Response of Root Volume to Different Liming Material* TREATMENT ROOT VOLUME (cm3) Ankasa Series Tikobo Series Un-amended 1.20a 1.45a LiN0P0 3.25c 3.33b CC500 2.15b 3.98bc CC700 3.38c 4.63c RH500 3.28c 5.99d RH700 3.15c 3.89bc CV% 12.8 *Li = CaCO3; N0 = zero N application; P0 = zero P application. Means with the same alphabet are not significantly (p>0.05) different. 85 University of Ghana http://ugspace.ug.edu.gh Effect Liming on Root Dry Matter The root dry mass of soya bean in the un-amended Ankasa Series was 0.21 g (Table 4.5). On amendment with CaCO3, the mass increased significantly (p<0.05) to 0.31 g. Amending the soil with RH500, though was superior to the un-amended soil did not increase the root mass (0.28 g) significantly (p>0.05) from that of the CaCO3 amendment. The other biochar liming materials, however, increased root mass significantly above that of the CaCO3 even though there were no significant differences among them, (the root masses were between 0.39g and 0.42 g). In the un-amended Tikobo Series, root mass of the soya bean plant was 0.14 g (Table 4.5). Amending the soil with CaCO3 increased the mass six fold to 0.84 g. Unlike in the Ankasa Series, the roots in the CaCO3 amended Tikobo Series were heavier than in their biochar amended counterparts. The biochar amended Tikobo soil showed only a 2.0 to 4.5 fold increase in root mass with the highest of 0.63 g being harvested from the RH500 amended Tikobo soil. Effect of Liming on Shoot Dry Matter Shoot dry matter of soya bean plants harvested from the un-amended Ankasa soil was 0.22 g similar to its root dry mass (0.21 g) (Table 4.6). Liming with CaCO3 significantly (p<0.05) gave the highest shoot dry matter of 0.53 g. Amending Ankasa with the four biochar types produced plants with shoot dry matter in the order of CC700 > CC500 = RH500 > RH700. The least shoot dry matter of 0.28 g was from the RH700 pot but significantly (p<0.05) heavier than that of the un-amended soil. 86 University of Ghana http://ugspace.ug.edu.gh Table 4. 5: Response of Root Dry Matter to Different Liming Materials* TREATMENT ROOT DRY MATTER (g) Ankasa Series Tikobo Series Un-amended 0.21a 0.14a LiN0P0 0.31b 0.84e CC500 0.42c 0.21b CC700 0.39c 0.23b RH500 0.28b 0.63d RH700 0.41c 0.35c CV% 10.3 *Li = CaCO3; N0 = zero N application; P0 = zero P application. Means with the same alphabet are not significantly (p>0.05) different. 87 University of Ghana http://ugspace.ug.edu.gh Table 4. 6: Response of Shoot Dry Matter to Different Liming Materials* TREATMENT SHOOT DRY MATTER (g) Ankasa Series Tikobo Series Un-amended 0.22a 0.26a LiN0P0 0.53e 0.63d CC500 0.35c 0.34b CC700 0.44d 0.53c RH500 0.34c 1.10f RH700 0.28b 0.72e CV% 16.4 *Li = CaCO3; N0 = zero; N application; P0 = zero P application. Means with the same alphabet are not significantly (p>0.05) different. 88 University of Ghana http://ugspace.ug.edu.gh Shoot dry matter in the un-amended Tikobo Series was 0.26 g (Table 4.6). This increased to 0.63 g when the soil was amended with CaCO3. Amending the soil with the CC biochar types produced soya bean plant with shoot dry matter (CC500 = 0.34 g; CC 700 = 0.53 g) significantly (p<0.05) heavier than the un-amended soil but lower than the conventionally limed soil. The RH biochar types when amended to the Hapludult (Tikobo soils) produced soya bean plants with shoot dry matter significantly (p<0.05) heavier than those from the CaCO3 amended soil. Effect of P on Growth Parameters of Soya bean Effect of P on Root Volume The root volumes when the P equivalent from biochar was added from synthetic P source (TSP) to the lime amended Ankasa was 3.05 cm3, which was not significantly ( p>0.05) different from when the soil was amended with only CaCO3 (LiN0P0) (Table 4.7). The root volume of the Ankasa Series that had been conventionally limed and to which synthetic P had been applied was, however, significantly (p<0.05) higher than the un-amended soil. When synthetic P at the rate of 30 kg P/ha was added to the biochar amended Ankasa Series, root volume did not significantly (p>0.05) change from the volumes when only biochar was amended to the soil. When synthetic P from TSP was added to the CaCO3 limed Tikobo Series at biochar P equivalent rate, root volume increased from 3.33 cm3 to 4.19 cm3. An addition of synthetic P at the rate of 30 kg P/ha to the biochar amended Tikobo Series did not show any significant (p>0.05) change in root volumes of the soya bean plants from their biochar amended counterpart plants (Table 4.7). 89 University of Ghana http://ugspace.ug.edu.gh Table 4. 7: Effect of P on Root Volume* ROOT VOLUME (cm3) Treatment Ankasa Series Tikobo Series Un amended 1.20a 1.45a LiN0P0 3.25c 3.33b LiN0BEP 3.05c 4.19bc CC500N0P0 2.15b 3.98bc CC700N0P0 3.38c 4.63c RH500N0P0 3.28c 5.99d RH700N0P0 3.15c 3.89bc CC500N0P30 2.75bc 4.03bc CC700N0P30 2.8bc 3.38b RH500N0P30 2.95bc 4.83c RH700N0P30 3.18c 5.75d CV% 15.60 *Li = CaCO3;N0 = zero N application; P0 = zero P application; P30 = 30 kg P/ha application; BEP = Biochar Equivalent P application from TSP. Means with the same alphabet are not significantly (p>0.05) different. 90 University of Ghana http://ugspace.ug.edu.gh Effect of P on Root Dry Matter When synthetic P at the biochar equivalent was applied to the CaCO3 amended Ankasa Series (LiN0BEP), root mass increased significantly (p<0.05) 0.21 g to 0.30 g in the un-amended soil (Table 4.8). However, this increase was not significantly (p>0.0) different from that of the CaCO3 limed soil with no external P application. On addition of synthetic P at 30 kg /ha to the biochar amended Ankasa Series, an increase in root mass was observed only in the RH amended soil (RH700N0P30) in which root mass increased from 0.41 g to 0.54 g (Table 4.8). Addition of synthetic P to the limed Tikobo Series produced soya bean plants with lighter roots as root mass decreased from 0.84 g in the unfertilized conventionally limed soil to 0.53 g in the un limed but P fertilized counterpart (LiN0BEP) (Table 4.8). In general, the addition of synthetic P to the biochar amended Tikobo Series produced heavier roots than their counterparts which were not synthetically fertilized. Effect of P on Shoot Dry Matter The effect of P from biochar and synthetic sources and their respective interactions on shoot dry matter of soya bean plants grown in the two soils are shown in Table 4.9. From the Table, addition of TSP at biochar equivalent P/ha to the CaCO3 limed Ankasa had no significant (p>0.05) effect on shoot dry matter just as root volume as the parameter was statistically not different from that in the unfertilized CaCO3 limed soil. It was only the P fertilized RH biochar amended soils that increased in shoot dry matter over their unfertilized P counterparts. There was about 1.65 times increase in shoot dry matter when the CaCO3 limed Tikobo Series was fertilized with TSP (Table 4.9). On further TSP fertilization of the RH limed Tikobo soils, 91 University of Ghana http://ugspace.ug.edu.gh Table 4. 8: Response of Root Dry Matter to Different P Source* ROOT DRY MATTER (g) Treatment Ankasa Series Tikobo Series Un amended 0.21a 0.14a LiN0P0 0.31bc 0.84 LiN0BEP 0.30b 0.53e CC500N0P0 0.42d 0.21b CC700N0P0 0.39cd 0.23b RH500N0P0 0.28b 0.63f RH700N0P0 0.41c 0.35c CC500N0P30 0.26ab 0.46d CC700N0P30 0.36c 0.69g RH500N0P30 0.27b 0.50d RH700N0P30 0.54e 0.94i CV% 8.60 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = 30 kg P/ha application; BEP = Biochar Equivalent P application from TSP. Means with the same alphabet are not significantly (p>0.05) different. 92 University of Ghana http://ugspace.ug.edu.gh Table 4. 9: Response of Shoot Dry Matter to Synthetic and Biochar P Sources* SHOOT DRY MATTER (g) Treatment Ankasa Tikobo Un amended 0.22a 0.26a LiN0P0 0.53cd 0.63c LiN0BEP 0.35bc 1.04e CC500N0P0 0.35bc 0.34a CC700N0P0 0.44c 0.53b RH500N0P0 0.34b 1.10e RH700N0P0 0.28b 0.72cd CC500N0P30 0.44c 0.54bc CC700N0P30 0.46cd 0.65c RH500N0P30 0.55d 0.57bc RH700N0P30 0.80e 0.78d CV% 12.70 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP. Means with the same alphabet are not significantly (p>0.05) different. 93 University of Ghana http://ugspace.ug.edu.gh shoot dry matter increased significantly (p<0.05) over the unfertilized counterparts. The converse was observed in the CC amended Tikobo soils. Effect of P on Nodulation The effect of P on nodulation is presented in Table 4.10. From the table, it is obvious that apart from RH700, all the biochar types only nodulated in Tikobo Series when they received synthetic P fertilization. On addition of TSP at the rate of 30 kg P/ha, the CC500 and CC700 which could not produce soya bean plants with nodules had plants with four and five nodules, respectively and the nodules weighed 0.004 g. The unfertilized RH500 which hitherto could not produce nodulated soya bean plants, produced plants with five nodules which weighed 0.004 g when fertilized with synthetic P at the rate of 30 kg P/ha. The unfertilized RH700 amended Tikobo Series which produced soya bean plants with 11 nodules had reduction in nodule numbers to 7 on addition of 30 kg P/ha from TSP. Effect of N Application on Growth Characteristics of Soya Bean Nitrogen is one of the main nutrients that control nodulation. It also affects chlorophyll content and hence dry matter production (Marschner, 1998). Effect of N on Shoot Dry Matter The sole effect of N on shoot dry matter of soya bean grown on the CaCO3 limed Ankasa and Tikobo Series are presented in Figure 15. Generally, with the exception of the RH700 amended 94 University of Ghana http://ugspace.ug.edu.gh Table 4. 10: Effect of P on Nodule Number and Nodule Dry Weight* TIKOBO Treatment Nodule Number Nodule Dry weight(g) Un amended 0 0 LiN0P0 0 0 LiN0BEP 0 0 CC500N0P0 0 0 CC700N0P0 0 0 RH500N0P0 0 0 RH700N0P0 11 0.011 CC500N0P30 4 0.004 CC700N0P30 5 0.004 RH500N0P30 5 0.004 RH700N0P30 7 0.016 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha ; BEP = Biochar Equivalent P application from TSP 95 University of Ghana http://ugspace.ug.edu.gh 1.4 1.2 N0 N10 1 0.8 0.6 0.4 0.2 0 AK AK AK AK AK TK TK TK TK TK Li CC500CC700RH500 RH700 Li CC500CC700RH500RH700 Treatments Figure 15. Response of shoot dry mass to N application 96 Shoot dry weight (g) University of Ghana http://ugspace.ug.edu.gh Ankasa Series, all the amended soils did not show any response to N application. When N from urea was applied at 10 kg/ha to the RH700 amended Ankasa Series, shoot dry matter increased by almost 2.1 times from 0.28 g to 0.58 g. Effect of N on root volume and Nodule Number The effect of N application on root volume of the two soils is presented in Figure 16. It is apparent from the figure that N application at 10 kg N/ha had no effect on root volume as unfertilized limed soils and fertilized limed soils both produced plants with statistically similar root volumes. The effect of synthetic N applied at 10 kg/ha on nodule number is presented in Figure 17. It was only the unfertilized RH700 Tikobo Series that produced nodules upon liming the soils. However, when the soil was fertilized with 10 kg N/ha from urea, nodulation was suppressed to nil. The CC700 amended Tikobo Series which had no nodules on the soya bean plants surprisingly, and inexplicably produced on the average 8 nodules on N fertilization Interactive Effects of Biochar Liming, Synthetic P and N Application on Growth Characteristics The interactive effects of biochar as a liming material, synthetic P and N on some growth characteristics of soya bean are presented in Table 4.11. The RH amended Ankasa Series that had been fertilized with both urea and TSP at respective rates of 10 kg N/ha and 30 kg P/ha produced plants with higher root volumes than their CC amended counterparts. The RH 500 and 700 with both P and N fertilization had respective root volumes of 3.99 and 4.28 cm3 compared to their CC 97 University of Ghana http://ugspace.ug.edu.gh 7 6 N0 N10 5 4 3 2 1 0 AK AK AK AK AK TK TK TK TK TK Li CC500CC700RH500 RH700 Li CC500CC700RH500RH700 Treatments Figure 16. Response of root volume to N applica 12 NO N10 10 8 6 4 2 0 Unamended Li CC500 CC700 RH500 RH700 Treatments Figure 17. Response of nodulation to N application 98 Root volume (cm3) Nodule number University of Ghana http://ugspace.ug.edu.gh Table 4. 11: Interactive Effects of Amendment on Root Volume, Shoot Dry Matter and Nodule Number in Ankasa Series* TREATMENTS ROOT VOL. SHOOT DRY MAT. NODULE NUMBER cm3 (g) Un-amended 1.20a 0.22a 0 LiN0P0 3.25cd 0.53fg 0 CC500N0P0 2.15b 0.35c 0 CC700N0P0 3.38cd 0.44de 0 RH500N0P0 3.28c 0.34c 0 RH700N0P0 3.15cd 0.28b 0 LiN0BEP 3.05c 0.35c 0 CC500N0P30 2.75bc 0.44de 0 CC700N0P30 2.80bc 0.46e 0 RH500N0P30 2.95bc 0.55fg 0 RH700N0P30 3.18cd 0.80i 0 LiN10P0 3.50cd 0.58g 0 CC500N10P0 2.21bc 0.35c 0 CC700N10P0 3.20cd 0.46e 0 RH500N10P0 2.73bc 0.41d 0 RH700N10P0 2.50bc 0.58g 0 LiN10BEP 2.23bc 0.33c 0 CC500N10P30 2.25bc 0.44de 0 CC700N10P30 2.23bc 0.56g 0 RH500N10P30 3.99d 0.63h 0 RH700N10P30 4.28d 0.51f 0 CV% 18.10 10.70 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha ; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. 99 University of Ghana http://ugspace.ug.edu.gh counterparts with root volumes of 2.25 cm3 and 2.23 cm3, respectively. The RH amended soils which had been fertilized with both N and P had significantly higher root volumes than those that had been fertilized with only N as soya bean plants grown in RH500N10P0 and RH700N10P0, respectively increased in root volumes from 2.21 cm3 and 3.2 cm3 to 3.99 cm3 and 4.28 cm3 when the treatments were further fertilized with P at 30 kg/ha. Addition of P from TSP did not however, increase root volume in the CC amended Ankasa Series significantly (Table 4.11) Generally, with the exception of RH 700, addition of both synthetic N and P increased shoot dry matter more than addition of N to the biochar amended plots. Shoot dry matter in the Ankasa Series was highest (0.63 g) in the P and N fertilized RH500 and least in the fertilized CC500 amended soil (0.44 g) Just as was observed in the Ankasa Series, the RH amended Tikobo soils produced plants with higher root volumes than their CC counterparts when the soil was fertilized with both urea and TSP (Table 4.12) with a general concomitant increase in shoot dry matter. Shoot dry matter upon N and P fertilization in the biochar amended soils was in the order of RH700N10P30 > RH500N10P30 >= CC700N10P30 > CC500N10P30 (Table 4.12). When both fertilizers were applied to the biochar amended Tikobo Series shoot dry matter, except in the RH500N10P30 amended soil was higher than in the counterparts that had received only N fertilization. Addition of both synthetic fertilizers to the biochar amended soils generally produced plants with nodules except in the RH500N10P30 Tikobo amended soil. It is worthy of note that none of the conventionally limed Tikobo soil produced plants with nodules whilst all the biochar amended soils with additional P at 30kg/ha produced between 4 and 7 nodules per plant (Table 4.12). When 100 University of Ghana http://ugspace.ug.edu.gh Table 4. 12: Interactive Effect of Amendment on Root Volume, Shoot Dry Matter and Nodule Number in Tikobo Series* TREATMENTS ROOT VOL. SHOOT DRY MAT. NODULE NUMBER (cm3) (g) Un-amended 1.45a 0.26a 0 LiN0P0 3.33bc 0.63e 0 CC500N0P0 3.98cd 0.34b 0 CC700N0P0 4.63d 0.53d 0 RH500N0P0 5.99e 1.10j 0 RH700N0P0 3.89cd 0.72f 11 LiN0BEP 4.19c 1.04i 0 CC500N0P30 4.03c 0.54d 4 CC700N0P30 3.38bc 0.65e 5 RH500N0P30 4.83d 0.57d 5 RH700N0P30 5.75e 0.78g 7 LiN10P0 2.80b 0.78g 0 CC500N10P0 4.18cd 0.45c 0 CC700N10P0 3.68c 0.41c 8 RH500N10P0 4.99de 1.00hi 0 RH700N10P0 4.25c 0.72f 0 LiN10BEP 3.03bc 0.42c 0 CC500N10P30 4.43c 0.78g 6 CC700N10P30 4.93d 0.99h 7 RH500N10P30 5.25de 0.96h 0 RH700N10P30 4.75de 1.08ij 8 CV% 18.10 10.70 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. 101 University of Ghana http://ugspace.ug.edu.gh N from urea at 10 kg/ha was added to the biochar amended Tikobo Series without synthetic P supplementation, only the CC700 amended soil produced nodules. Nutrient Uptake Phosphorus is the most limiting macro nutrient with regards to nodulation in soya bean. The availability of the nutrient is also controlled by pH and hence liming. Thus, this section will focus on uptake of P in the root and shoot. Root P Uptake Root P uptake from soya bean plants grown in the Ankasa Series is presented in Table 4.13. Root P uptake in the un-amended Ankasa series was 2.15 mg/pot which increased significantly (p<0.05) to 6.79 mg/pot when the soil was limed with CaCO3. Amending the soil with biochar increased root P uptake significantly (p<0.05) when compared to CaCO3 limed soil except in the RH500 amended soil where uptake decreased. When the biochar equivalent P from TSP was added to the CaCO3 limed soil, root uptake increased significantly (p<0.05) to 7.14 mg/pot. However, this uptake was not statistically (p>0.05) different from the uptake levels in the RH700 and CC700. Further addition of synthetic P from TSP at the rate of 30 kg P /ha only gave a significant (p<0.05) increase in P uptake (12.75 g) in the RH700 amended soil. It is apparent from the Table that addition of 10 kg N/ha from urea (LiN10P0) increased uptake of P significantly (p<0.05) to 12.49g, 1.75 times more than when no N was applied to the CaCO3 limed soil. However, application of both N and P to the CaCO3 limed soil suppressed P uptake to 7.24 g similar to when no synthetic N and P were applied (6.79 g). Root P uptake in unfertilized biochar amended Ankasa series were similar to both the unfertilized and P fertilized 102 University of Ghana http://ugspace.ug.edu.gh Table 4. 13: Effect of Amendments on Root P Uptake* TREATMENTS ROOT P UPTAKE (mg/pot) Ankasa Tikobo Un-amended 1.45a 1.55a LiN0P0 9.93cd 17.13g CC500N0P0 5.15b 4.56b CC700N0P0 5.35b 5.49b RH500N0P0 6.62bc 14.45f RH700N0P0 5.45b 7.97c LiN0BEP 5.84b 12.58ef CC500N0P30 9.17c 11.06d CC700N0P30 9.22c 13.91f RH500N0P30 12.44d 12.00e RH700N0P30 16.24e 22.77h LiN10P0 9.40cd 8.63cd CC500N10P0 7.37bc 4.56b CC700N10P0 9.49cd 8.78cd RH500N10P0 8.74c 12.01e RH700N10P0 11.41cd 12.95ef LiN10BEP 7.88bc 9.77d CC500N10P30 11.00cd 21.62h CC700N10P30 12.87d 14.40f RH500N10P30 12.35d 22.92h RH700N10P30 12.10d 17.42g CV% 11.00 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. a. 103 University of Ghana http://ugspace.ug.edu.gh CaCO3 limed soil except in the CC500 amended Ankasa Series with a higher P uptake of 9.8 g. Phosphorus fertilization from TSP to the biochar amended soil gave an increase in P uptake (12.75 g) only in the RH700N0P30 Ankasa soil. Addition of both urea and TSP at their respective rates to the biochar amended soils did not generally increase root P uptake. Root P uptake in the Tikobo Series was generally higher than in the Ankasa Series when either of both of the synthetic fertilizers were added. Liming the soil with CaCO3 increased P uptake from 1.55 g in the un-limed soil to 17.13 g which upon addition of the biochar equivalent P from TSP was suppressed to 12.58 g. Addition of both P and N to the CaCO3 limed soil increased root P uptake to 21.62 g. The addition of biochar to the Tikobo Series though increased root P uptake above that of the un- amended had values significantly lower than that in the CaCO3 limed soil. When TSP was added to the biochar amended Tikobo Series at 30 kg P/ha, P uptake increased over that when synthetic P was not applied. On addition of synthetic P to the biochar amended Tikobo Series, root uptake was in the order of RH700N0P30 > CC700N0P30 > RH500N0P30 = CC500N0P30. Nitrogen application to the biochar limed and CaCO3 limed soils increased root P uptake over when the soil was not fertilized. However, these uptake P values were expectedly lower than when synthetic P was added. On addition of synthetic P and N to the biochar limed Tikobo Series, P uptake of roots were significantly enhanced with the CC500N10P30 and RH500N10P30 treatments having the highest P root uptake. 104 University of Ghana http://ugspace.ug.edu.gh Shoot P Uptake Shoot P uptake recorded after harvest is presented in Table 4.14. In the two soils, the amended soils were significantly (p˂0.05) higher than the un-amended soil. The un-amended soil recorded shoot P uptake of 2.15 mg/pot. Soil amended with rice husk biochar charred at 700 oC with the addition of 30 kg P/ha synthetic fertilizer gave the highest shoot P uptake (16.24 mg/pot). Shoot P uptake was generally higher in Ankasa Series amended with the biochar types than the CaCO3 and the un-amended soils. Tikobo Series on the other hand, recorded shoot P uptake of 3.46 mg/pot to 25.67 mg/pot. The un- amended soil recorded the lowest shoot P uptake of 3.46 mg/pot. Soil amended with rice husk biochar charred at 700 oC with the addition of 10 kg N/ha and 30 kg P/ha synthetic fertilizer gave the highest P uptake of 25.67 mg/pot. Generally, shoot P uptake was higher in soils amended with the biochar types than in the CaCO3 and the un-amended soils. All the amended soils were significantly (p<0.05) different from the un-amended soils. 4.12. Soil Residual Total C, Total N, Total P and Available P. The residual total C, total N, total P and available P for Ankasa Series are presented in Table 4.15. The initial organic carbon content of the Ankasa Series (Table 1) was 15.3 g/kg and this did not vary much from the residual carbon content of 15.95 g/kg after harvest. The unfertilized CaCO3 amended treatment (LiN0P0), the CaCO3 amended with P equivalent from biochar (LiN0BEP) and the N fertilized CaCO3 amended soil (LiN10P0) also had statistically similar carbon content of 16.23 g/kg, 16.25 g/kg and 17.16 g/kg, respectively after harvest. The LiN10BEP which is the N and P 105 University of Ghana http://ugspace.ug.edu.gh Table 4. 14: Effect of Amendments on Shoot P Uptake* TREATMENTS SHOOT P UPTAKE (mg/pot) Ankasa Tikobo Un-amended 2.15a 3.46a LiN0P0 6.79cd 12.59cd CC500N0P0 9.80e 6.32b CC700N0P0 8.72de 12.71cd RH500N0P0 3.76b 18.49ef RH700N0P0 8.96de 14.47de LiN0BEP 7.14cd 11.55cd CC500N0P30 6.23c 17.34ef CC700N0P30 8.44de 12.82c RH500N0P30 6.54cd 16.87e RH700N0P30 12.75f 14.88de LiN10P0 12.49f 13.84d CC500N10P0 4.98bc 11.37cd CC700N10P0 8.17d 11.55cd RH500N10P0 7.44c 17.15e RH700N10P0 15.19g 16.44de LiN10BEP 7.24cd 10.02c CC500N10P30 8.33d 20.00f CC700N10P30 8.32de 19.21ef RH500N10P30 12.86f 19.26ef RH700N10P30 7.97d 25.67g CV% 16.10 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. 106 University of Ghana http://ugspace.ug.edu.gh fertilized CaCO3 amended Ankasa Series had a higher carbon content (20.24g/kg) than the original soil (15.95). The biochar amended Ankasa soils had significantly (p<0.05) higher residual total carbon contents than the CaCO3 limed soils. The residual carbon contents in the Ankasa Series irrespective of synthetic fertilization was generally higher in the RH amended soils than the CC amended soils in the order of RH > CC500 = CC700 Total C recorded on biochar amended soils were significantly (p˂0.05) different from the un- amended soil. Rice husk biochar charred at 500 0C without addition of N and P fertilizers gave the highest total C (52.79 g/kg). As was observed for total carbon contents in the residual soil total N (TN) was generally statistically (p>0.05) similar in all the CaCO3 limed and un-amended soils with TN values between 0.76 g/kg and 0.92 g/kg. The residual TN contents in the un-amended and CaCO3 limed soil were lower than the initial TN (1.6 g/kg). The residual TN in the biochar amended soils though lower than the original soil to which the material was amended, was higher than in the CaCO3 limed soils with concentrations between 1.07 g/kg and 1.4 g/kg. Total P (TP) in the residual un-amended (171.3) Ankasa Series did not vary much from that of the original soil (164 g/kg). The CaCO3 limed soils irrespective of whether they had been fertilized or not had higher TP concentrations ranging between 252.6 and 281 g/kg. The higher TP concentrations in the CaCO3 limed soils than the un-amended soils also reflected in a much higher available P in the CaCO3 limed soils with available P increasing from 1.54 g/kg in the original un- amended Ankasa Series to between 6.65 and 13 g/kg. In fact, the CaCO3 limed soil but 107 University of Ghana http://ugspace.ug.edu.gh Table 4. 15: Effect of Amendments on TC, TN, TP and AP in Ankasa Series* TREATMENTS TC(g/kg) TN(g/kg) TP(mg/kg) AP(mg/kg) Un-amended 15.95a 0.92b 171.30a 3.25a LiN0P0 16.23a 0.87ab 281.00b 6.65a CC500N0P0 33.11cd 1.22d 344.90f 13.55bc CC700N0P0 31.73c 1.25de 291.70c 15.90c RH500N0P0 52.79g 1.20cd 307.2c 26.60f RH700N0P0 45.99f 1.35def 324.6d 22.00de LiN0BEP 16.25a 0.90ab 264.30b 13.00b CC500N0P30 35.83cd 1.34def 309.4c 19.70de CC700N0P30 35.33d 1.29def 302.9c 20.65de RH500N0P30 37.88de 1.33def 301.1c 27.20fg RH700N0P30 45.35f 1.32def 314.4d 31.00g LiN10P0 17.16ab 0.91b 252.60b 10.15b CC500N10P0 36.16d 1.40f 311.00c 19.45d CC700N10P0 32.83cd 1.25de 319.6d 16.30cd RH500N10P0 39.71e 1.07c 322.1d 25.90ef RH700N10P0 44.25f 1.28def 303.3c 22.95e LiN10BEP 20.24b 0.76a 254.00b 12.30b CC500N10P30 39.77e 1.37ef 297.2cd 20.00de CC700N10P30 34.07c 1.14cd 320.8d 23.6ef RH500N10P30 44.39f 1.14cd 304.5c 30.45g RH700N10P30 42.53ef 1.25de 327.7df 23.05e CV% 10.00 13.17 5.60 13.70 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. a. 108 University of Ghana http://ugspace.ug.edu.gh unfertilized Ankasa Series (LiN0P0) had an almost four-fold increase in available P whereas its counterpart that had received 10 kg/ha N increased more than six fold to 10.15 mg/kg. The biochar amended soils conspicuously had statistically (p<0.05) much high TP and available P concentrations in the residual Ankasa Series. Total P concentration in the biochar amended soils almost doubled over that of the initial soils as values ranged between 291.7 mg/kg and 344 mg/kg. Concomitantly, available P concentrations in the biochar amended soils were high. Available P were higher in the RH amended soils than their CC amended counterparts. Expectedly, residual available P in the TSP amended soils were higher than the soils that had not been fertilized with P. The initial total carbon content in the Tikobo Series of 5.4 was not significantly (p>0.05) different from the residual un-amended soil and its CaCO3 limed counterparts (Table 4.16). On amendment with biochar which had between 387.1 and 602.9 g/kg C (Table 2), residual C contents of the Tikobo Series increased over that of the un-amended soil to values between 18.88 g/kg to 21.88 g/kg. There were generally no significant (p>0.05) differences among biochar amended Tikobo soil Series (Table 4.16). Total N which was 1.2 g/kg in the initial Tikobo Series decreased to 0.35 g/kg in the residual un-amended soil and to lower concentration (0.13 -0.16 g/kg) in the CaCO3 amended Tikobo Series irrespective of whether they were fertilized or not. The TN in the biochar amended soils (0.42 - 0.62 g/kg) was significantly (p<0.05) higher than in the un-amended soils though lower than the initial soil. The residual TP in the un-amended Tikobo Series (127.4 mg/kg) was higher than the initial value (101.4 mg/kg) but significantly (p˂0.05) lower than the CaCO3 amended soils (152.8 mg/kg – 174.1 mg/kg). The increase in TP in the CaCO3 limed soils also reflected in an increase in their. 109 University of Ghana http://ugspace.ug.edu.gh Table 4. 16: Effect of Amendments on C, N, TP and AP in Tikobo Series* TREATMENTS TC(g/kg) TN(g/kg) TP(mg/kg) AP(mg/kg) Un-amended 7.42a 0.35b 127.40a 3.15a LiN0P0 7.31a 0.18a 170.30bc 7.80b CC500N0P0 20.47b 0.62c 203.00d 13.55c CC700N0P0 19.32b 0.57c 235.70e 15.90cd RH500N0P0 20.71b 0.51c 253.40ef 25.65ef RH700N0P0 18.88b 0.47bc 257.80f 22.55e LiN0BEP 7.22a 0.16a 174.10c 10.05b CC500N0P30 19.32b 0.55c 256.90f 21.30de CC700N0P30 19.49b 0.58c 249.70ef 19.70de RH500N0P30 20.17b 0.48bc 242.50ef 28.80f RH700N0P30 20.89b 0.44bc 239.90ef 31.95f LiN10P0 7.64a 0.14a 158.90bc 5.50a CC500N10P0 19.64b 0.60c 252.70ef 18.70d CC700N10P0 21.88b 0.55c 255.30f 15.70cd RH500N10P0 19.86b 0.47bc 244.80ef 25.90ef RH700N10P0 20.45b 0.42bc 247.70ef 22.95e LiN10BEP 7.66a 0.13a 152.80b 9.50b CC500N10P30 19.55b 0.55c 248.50ef 22.90e CC700N10P30 19.96b 0.54c 252.80ef 23.90e RH500N10P30 22.20b 0.46bc 250.10ef 30.45f RH700N10P30 20.78b 0.45bc 247.90ef 23.05e CV% 10.00 13.17 5.60 13.70 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. 110 University of Ghana http://ugspace.ug.edu.gh respective available P. Available P increased from 2.71 in the initial soil to between 5.5 mg/kg and 10.05 mg/kg. The residual TP in the biochar amended Tikobo Series was higher than the CaCO3 and the un-amended soils as presented in Table 4.16. Residual TP concentrations in biochar amended soils (203 mg/kg – 257.8 mg/kg) were two times higher than in the initial soil (101.4 mg/kg). As a consequence of the higher TP in the biochar amended Tikobo Series, available P increased in the soil. Increases in available P concentrations five times more than that in the initial soil. In fact, RH500 application without any other form of fertilization increased available P concentrations almost 9.5 times to 25.65. Just as was observed in the Ankasa Series, RH amended soil increased residual available P concentrations more than its CC counterparts. 4.12. Effect of Amendment on Soil Residual Exchangeable Acidity and pH The soil residual pH and exchangeable Al for both Ankasa and Tikobo Series are summarized in Table 4.17. Concentration of Al in the initial Ankasa Series and Tikobo Series used for the study were 1.31 and 0.4 cmol/kg, respectively. After harvest, the residual exchangeable Al did not change in the un-amended soils. The residual pH of the un-amended soils was 4.1 and 4.6, respectively just as observed in the initial soil prior to crop cultivation. After liming with CaCO3, the residual Al reduced to between 0.47 and 0.59 cmol/kg with a concomitant increase in residual pH of between 4.7 and 5.0 for the Ankasa Series. Amending the Ankasa Series with biochar reduced Al concentration from 1.31 cmol/kg to between 0.15 and 0.59 cmol/kg. The residual Al in the unfertilized amended biochar Ankasa Series were the least ranging between 0.15 and 0.32 cmol/kg. These least residual exchangeable Al were accompanied by corresponding higher pH between 4.9 and 5.2. The fertilized biochar amended Ankasa series generally had higher residual Al contents when compared to the unfertilized biochar amended soils. 111 University of Ghana http://ugspace.ug.edu.gh Table 4. 17: Effect of Amendment on Residual Al and pH* TREAMENTS Al(cmolc/kg) pH ANKASA TIKOBO ANKASA TIKOBO Un-amended 1.27g 0.39e 4.1 4.6 LiN0P0 0.47e 0.21cd 4.7 4.8 CC500N0P0 0.24bc 0.00a 5.1 5.4 CC700N0P0 0.32cd 0.00a 4.9 5.5 RH500N0P0 0.29c 0.00a 4.9 5.8 RH700N0P0 0.15a 0.00a 5.2 5.8 LiN0BEP 0.55f 0.24d 4.5 4.7 CC500N0P30 0.31cd 0.00a 4.8 5.7 CC700N0P30 0.35cd 0.00a 5 5.8 RH500N0P30 0.20ab 0.00a 4.8 5.6 RH700N0P30 0.29c 0.00a 4.9 5.5 LiN10P0 0.59f 0.15c 4.6 4.9 CC500N10P0 0.35cd 0.00a 5.1 5.6 CC700N10P0 0.30cd 0.00a 4.8 5.7 RH500N10P0 0.29c 0.00a 5.1 5.7 RH700N10P0 0.22b 0.00a 4.9 5.6 LiN10BEP 0.53e 0.09b 4.8 5 CC500N10P30 0.36d 0.00a 4.7 5.8 CC700N10P30 0.41de 0.00a 5.2 5.8 RH500N10P30 0.25bc 0.00a 4.9 5.8 RH700N10P30 0.37d 0.00a 5.1 5.6 CV% 18.10 *Li = CaCO3; N0 = zero N application; P0 = zero P application; P30 = TSP applied at a rate of 30 kg P/ha; BEP = Biochar Equivalent P application from TSP; N10 = 10 kg N/ha from urea. Means with the same alphabet are not significantly (p>0.05) different. 112 University of Ghana http://ugspace.ug.edu.gh Liming the Tikobo series with CaCO3 reduced Al concentrations from 0.40 cmol/kg to levels between 0.09 cmol/kg and 0.24 cmol/kg with a corresponding residual pH between 4.8 and 5. Amending the Tikobo Series with biochar, irrespective of whether the soil had been fertilized or not, reduced exchangeable Al to undetectable levels in the soil after harvest with a concomitant rise in residual pH to between 5.4 and 5.8 113 University of Ghana http://ugspace.ug.edu.gh CHAPTER FIVE 5 DISCUSSION Soil Characterization The higher sand but lower clay contents in the Tikobo Series than the Ankasa Series is as a result of the different parent materials from which the two soils were developed. Tikobo Series has developed from tertiary sand whilst Ankasa Series has been developed from granite (Dwomo and Dedzoe, 2010). It therefore stands to reason that the Tikobo Series has more sand. Ankasa Series was sampled from a forest reserve and as a result of its high litter fall, organic carbon content was almost 2.8 times more than that in the Tikobo Series. It is, therefore, a matter of consequence that coupled with its higher clay content, the Ankasa Series will have a lower bulk density than the Tikobo series as observed in their characterizations. Hudson (1994) reported decrease in bulk density of soils with different textural classes due to the addition of organic matter. The extremely acid and lower pH in Ankasa Series compared to the Tikobo Series is as a result of the higher exchangeable Al in the former soil. The differences in pH in salt and water (i.e. ΔpH = pHCaCl2 - pHH2O) gave negative values which show that, there are negative charges on the surfaces of both soils (Nartey, et al., 1997). The Tikobo and Ankasa Series both occur in the tropical evergreen rainforest of Ghana. However, the Ankasa Series is from a forest reserve where there is continuous litterization from the vegetative cover. The thick forest cover creates a micro climate with relatively lower temperature compared to the fallow plots from which the Tikobo Series was sampled. With the associated lower pH, there is likely to be lower low microbial activity and therefore slower decomposition 114 University of Ghana http://ugspace.ug.edu.gh rate of organic matter and this may, in part explain the higher organic carbon content in the Ankasa Series (Giller et al. 2001). The higher CEC of the Ankasa Series over the Tikobo Series is due to the higher organic carbon and clay contents of the former. The CEC which is a measure of charges at the colloidal surfaces was determined in this study by the ammonium acetate method at pH 7. This pH is 2.8 pH units above that in water for Ankasa and 2.1 pH above that for Tikobo.The ECEC on the other hand, is a measure of the exchangeable cations at the colloidal surface at the soil’s pH (Evangelou, 1998). In this study, the ECEC was determined by the summation of exchangeable cations in the two soils. Thus with CEC being determined at pH above that of the two soils, it is expected that more negative charges would be created and hence higher CEC. The measured CEC of the two soils at pH 7 is in fact their respective potential CECs This may partly account for the higher CEC than ECEC in the two soils. The high rainfall in the Evergreen Forest belt of Ghana which is above 2000 mm (MoFA, 2012) has led to leaching of bases as evident in the low exchangeable base concentration of the soils. This has culminated in high Al saturation of the soil accounting for the 54.8% and 24.54% for Ankasa and Tikobo Series, respectively. The Al saturation of the soils which is higher than the critical of 15% for optimum soya bean production (Fageria and Baligar, 2008) is likely to cause soya bean grown on especially Ankasa Series to have restricted root development, poor nodulation and general poor growth in the Ankasa Series (Kochian, 1995). The high Al saturation, low pH, coupled with the high kaolinite and sesquioxides content that are likely to be the major minerals in Ultisols and Oxisols (Evangelou, 1998) would make the two soils prone to high P sorption (Nartey et al., 1997). Consequently, the two soils are low in available phosphorus status. 115 University of Ghana http://ugspace.ug.edu.gh Biochar Characterization The slightly higher total bases in the corn cob feedstock (0.93%) than that in the RH feedstock (0.9%) might have accounted for the higher pH of 6.8 in the CC feedstock than the RH feedstock value of 6.1. Upon charring of the two feedstocks at temperatures of 500 oC and 700 oC, there was liberation of three forms of bases viz. total, exchangeable and soluble. These liberated bases might have accounted for the rise in pH of the four biochar types from neutral to alkalinity. The strong alkalinity (pH between 10.7 and 11) in the CC biochar types is due to their high total and exchangeable bases. The increase in pH as a result of release of bases due to high charring temperature is corroborated by Struebel et al. (2011). High pyrolysis temperatures release organic acids and phenolic substances through cracking of hemicellulose and cellulose and in effect these acids react with basic cations in the feedstocks to form alkaline salts which increase the pH of biochar (Streubel, 2011; Shinogi and Kanri, 2003). Total Na and K were higher in the CC feedstock than the RH and consequently on charring the CC biochar types had higher total Na and K. Corn cob is from a fruit which tends to accumulate more sugar and hence K, especially in the pith (Purseglove, 1968) whereas rice husk though also from a grain and hence a fruit contains more Si. It is, therefore, not surprising that the CC feedstock and biochar types contain more K than their RH counterparts. The exchangeable Na and K were also generally higher in the CC biochar types than the RH biochar types implying that for availability of K, the CC biochar materials should be the preferred choice. However, the CC biochar types may impose drainage problems because of their high Na content that may disperse soils. Such CC biochar types should not be applied on salt affected soils. The RH feedstock had higher Ca and Mg contents and consequently higher contents of these secondary major nutrients 116 University of Ghana http://ugspace.ug.edu.gh in the total fractions upon charring. Joseph et al. (2010), has reported that most biochars are often alkaline and therefore increase soil pH after application. The high pH of corn cob biochar makes it suitable to lime highly acidic soils whilst rice husk biochar can be used to lime slightly acid soils. The total carbon contents of the biochar types were higher than their respective un-charred feedstocks. High heating rates have been found to provide a shorter time for the dehydration reactions and the formation of less reactive anhydrocellulose, leading to the production of biochar with a higher carbon yield (Zanzi, 2001). Generally, corn cob biochar types had higher carbon content than rice husk biochar types due to the high carbon content of the corn cob feedstock. Corn cob is more lignified and has more polyphenol groups than the rice husk (Masulil et al., 2010). Consequently, the CC would have more aromatic C groups (Shinogi and Kanri, 2003) and hence more recalcitrant carbon accounting for the higher accumulation of C after charring. The total nitrogen (TN) content of the biochar types as shown in Table 4.2 was inversely related to pyrolysis temperature. The TN content decreased with increasing pyrolysis temperature. The higher N in the un-charred feedstocks than the biochar can be attributed to volatilization of N on pyrolysis. Nitrogen is sensitive to heat and is subsequently volatilized leading to low N content of the biochar types. Corn cob is more lignified than rice husk and consequently more resistant to charring than RH. It is, therefore, not surprising that CC biochar types have more TN than their RH counterparts. The CC biochar types have high C: N ratio which may reduce microbial decomposition and restrict release of N from the biochar when added to the soil. According to Lehman and Joseph ( 2007), charring leads to carbonization of the biochar types culminating in high carbon contents per unit mass. With the concomitant decrease in their respective N contents, it is expected that the biochar types will have low C: N ratios than their respective feed stocks as reflected in values between 692 and 773 for the four biochar types as opposed to between 42 and 117 University of Ghana http://ugspace.ug.edu.gh 47 for their respective feedstocks. These very high C: N ratios of the biochar imparts stability on the material and thus would persist in soil for a very long time. The total P contents in the biochar were far higher than in the feedstocks from which they were charred and this was as a result of conversion of organic P to the inorganic form during pyrolysis. The release of the inorganic orthophosphate ions also combines with the liberated Ca to form Ca- P compounds which are not readily soluble and hence increasing significantly the total P contents of the biochar (Lehman, 2007). Shenbagavalli and Mahimairaja (2012) reported that charring of biomass can greatly enhance P availability from plant tissue by cleaving organic phosphorus bonds, to form soluble P salts in the charred materials. The rice husk biochar types generally had higher total P content than the corn cob biochar due to the higher inherent P content in the former’s feedstock. The very high Olsen P of about 2000 mg/kg in the four biochar types coupled with their high pH holds promise for exploitation of the materials for use as P source in tropical acid soils with high P sorption capacity Effect of Liming on pH and Availability of Bases. The increase in pH of the biochar and CaCO3 amended soils during the incubation period in both Ankasa and Tikobo Series is due to the release of readily available calcium from the five liming materials which replaced the Al3+ and H+ at the exchange sites of the respective soils as depicted in equation 5.1: Al3+ Ca2+ + 2CaCO3 + H2O + Al(OH)3 + 2CO2 [5.1] H+ Ca2+ Soil Colloid 118 University of Ghana http://ugspace.ug.edu.gh The replacement of Al3+ and H+ by Ca2+ is corroborated by decreases in Al3+ and H+ with concomitant increases of Ca2+ in solution of the two soils. This is further supported by significant correlation coefficient (R) of -0.78** between exchangeable Al and Ca for Ankasa Series and - 0.57** for Tikobo Series (Figure 18). The corresponding respective coefficient of determinations (R2) of 0.607 for Ankasa Series and 0.321 for Tikobo Series imply that 60.7% and 32.1% respective decreases in Al are attributable to Ca from the amendments. Thus Ankasa Series responds more to Ca for Al replacement than Tikobo Series. Apart from Ca, the four biochar types had Mg, Na and K. These three other basic cations might have also replaced part of the Al accounting for the much higher rise in pH of the biochar amended soils than the CaCO3 counterpart. These increases in pH of acid soils by biochar are corroborated by several authors (Novak et al., 2009; Joseph et al., 2010; Farrell et al., 2013; Masto et al., 2013; Masulili et al., 2016). A regression of the sum of Na, K and Mg in soil solution of the biochar amended Ankasa and Tikobo against their respective Al concentrations showed high negative correlation coefficient of -0.91** for Ankasa Series and -0.81** for Tikobo Series (Figure 19). Regressing the sum of the three bases on pH showed a positive correlation coefficient of 0.74** for Ankasa Series and 0.81** for Tikobo Series (Figure 20). Regressing soluble Al on soluble Mg gave R = -0.91**and pH versus Mg giving R = 0.83** for Ankasa Series (Figure 21a and 21b). The R value was 0.84** for Mg against pH and -0.77** for Mg against Al (Figure 22a and 22b). The higher correlation between Mg and Al in the biochar amended soils than Ca between Al in the CaCO3 amended soils show that Mg was more effective than Ca in reducing Al concentration in the soils. Dolomite could have, therefore been a better liming material than the CaCO3. 119 University of Ghana http://ugspace.ug.edu.gh 1.6 1.6 1.4 1.4 R² = 0.6067 Tikobo 1.2 1.2 Ankasa R² = 0.32081 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 1 2 3 0 1 2 3 Exch. Ca (cmol/ kg) Exch. Ca (cmol/ kg) Figure 18. Relationship between exchangeable Ca and exchangeable Al. 1.6 1.6 Ankasa Tikobo 1.4 1.4 1.2 (r= -0.91**) 1.2 (r= -0.81**) 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 2 4 0 2 4 Sum of Mg, K and Na (cmolc/ Sum of Mg, K and Na (cmolc/ kg kg soil) soil) Figure 19. Relationship between sum of bases (Mg, K, Na) and exchangeable Al. 120 Al (cmol/ kg soil) Exch. Al (cmol/ kg) Al (cmol/ kg soil) Exch. Al (cmol/ kg) University of Ghana http://ugspace.ug.edu.gh 6.5 6.5 Ankasa 6 Tikobo6 (r= 0.81**) (r=0.74**) 5.5 5.5 5 5 4.5 4.5 4 4 0 1 2 3 4 0 2 4 Sum of Mg, K and Na (cmol/ kg Sum of Mg, K and Na (cmol/ kg soil) soil) Figure 20 Relationship between sum of bases (Mg, K, Na) and pH. 1.6 Ankasa 6.5 1.4 (r= -0.91**) Ankasa6 1.2 (r=0.84**) 1 5.5 0.8 5 0.6 0.4 4.5 0.2 0 4 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 Exch. Mg (cmolc/ kg soil) Exch. Mg (cmolc/ kg soil) Figure:21a: Relationship between Figure 21b: Relationship between Exchangeable Al and Mg pH and Mg 121 Al (cmolc/ kg soil) pH pH pH University of Ghana http://ugspace.ug.edu.gh 1.6 Tikobo 6.5 1.4 (r= -0.77**) 6 1.2 Tikobo 1 5.5 0.8 (r=0.84**) 0.6 5 0.4 4.5 0.2 0 4 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 Exch. Mg (cmolc/ kg soil) Exch. Mg (cmolc/ kg soil) Figure 22a: Relationship between Figure 22b: Relationship between exchangeable Al and Mg pH and Mg 122 Al (cmolc/ kg soil) pH University of Ghana http://ugspace.ug.edu.gh In the CaCO3 amended soil, Tikobo changed from being very strongly acid to strongly acid whilst Ankasa became strongly acid. The slow response of Ankasa Series to liming was as a result of its high organic matter content which was about 2.8 times higher than that in Tikobo. This moderately high organic carbon content (15.3 g/kg) might have acted as a buffer resisting changes in pH as explained by Stewart et al. (2013) and Curtin and Trolove (2013). According to Campbell (1993), the more humus and clay a soil has, the greater its Al and H content and hence the greater the amount of lime needed to raise the soil pH. This explains the respective responses of Ankasa and Tikobo Series to the same rate of lime application during the incubation period. The increase in pH on amendment of Ankasa Series and Tikobo Series with CaCO3 is more than 0.5 pH unit which according to Nartey et al. (2000) is significant. This significant increase in pH from 4.2 to 4.7 and 4.9 to 5.2, respectively, for Ankasa and Tikobo Series might have led to the solubility of hitherto precipitated Mg and Na leading to the increases in the concentration of the two basic cations soil solution of the CaCO3 amended Ankasa Series. This may explain increases in Na and Mg concentrations in the CaCO3 amended soil even though the amendment did not have Mg and Na as active ingredients. The four biochar types have readily available basic actions in soluble and exchangeable forms and with the accompanying rise in pH upon amendment to the two acid soils, it stands to reason that the basic cations K, Mg and Na increased in solution. The highest concentrations of available Na in the two soils upon amendment with the biochar samples is due in part to its relatively higher abundance as a soluble cation in the four biochar types (0.04% - 0.08% as opposed to between 0.01% and 0.02% for Ca, K and Mg). Sodium, among the four bases is the most soluble (Evangelou, 1998) and with increase in pH should be the most abundant cation. 123 University of Ghana http://ugspace.ug.edu.gh Effect of Liming on P Availability The increase in P availability of the CaCO3 limed Ankasa and Tikobo Series is attributed to the decrease in Al concentration with a consequential increase in solution pH. The CaCO3 limed Ankasa Series decreased in Al saturation from 54.8% to 29.3% whilst the Tikobo decreased from 24.54% to 4.91%. These respective decreases led to pH increases from 4.2 to 4.7 and 4.9 to 5.2 respectively. These decreases in Al saturation with concomitant increases in pH might have led to solubilization of some of the total P in the two soils. These increases in available P concentrations as a result of decreases in Al concentration is evident in Figures 23. The significant negative correlation implies that as Al decreases availability of P increases. The respective coefficient of determinations R2 values were 0.95 and 0.98 respectively for Ankasa Series and Tikobo Series showing that between 95% and 98% of the available P in the CaCO3 limed soils is accounted for by decreases in soluble Al. The reasons accounting for the sharp increase in P availability in biochar amended soils is two- fold. Firstly, the liming effects of the biochar on the two soils were far higher than that of the CaCO3 because of the additional bases inherent in the biochar as previously discussed in section 5.3. Thus, Al saturation in the Ankasa Series was reduced from 54.8% to between 18% and 22% 124 University of Ghana http://ugspace.ug.edu.gh 14 12 12 Ankasa 10 Tikobo 10 (r= -0.98**) 8 8 (r=-0.99**) 6 6 4 4 2 2 0 0 0.5 1 1.5 0 0.2 0.4 0.6 Al (cmol/kg soil) Al (cmol/ kg soil) Figure 23 Relationship Between Available P and Al 125 Available P (mg/ kg soil) Available P (mg/ kg soil) University of Ghana http://ugspace.ug.edu.gh whilst the Tikobo Series reduced to non-detectable levels. These lower Al saturation in the biochar amended soils with the accompanying increase in pH may have led to higher dissolution of the total P in the soils into available forms. Secondly, the biochar types contain more than 2000 mg/kg available P an equivalent of 120 kg P /ha was from each biochar type. These high levels of available P added may have also led to the high availability of P in the biochar amended soils. The increase in soil available P levels following biochar application has been documented (Özenç and Özenç, 2009; Wang et al., 2012; Darfour, 2016). 5.5. Effect of Soil Amendments on Plant Growth Parameter The high Al saturation of 54.8% which is above the critical limit of 15% for optimum soya bean cultivation (Fageria and Baligar, 2008) coupled with the low pH in water of 4.2 and low concentration of Bray available P of 1.54 mg/kg contributed to restricted root development and expansion. It is, therefore, not surprising that the root volume in the un-amended Ankasa Series (1.2 cm3) was the least. On amending Ankasa Series with CaCO3 for six weeks, pH rose to 4.7 and Al saturation decreased to 29.3% with a concomitant increase in Ca to 0.89 cmol/kg and Mg to 0.35 cmol/kg. Available P then increased from 1.54 to 12.67 mg/kg. These contributed to the 2.7 times increase root volume in the Ankasa to 3.25 cm3. Amending the Ankasa Series with the biochar types increased pH from 4.2 to about 5.2. This increase in pH reduced Al saturation to between 18 and 22% for the CC and RH biochar types. Correspondingly, Ca concentration increased to about 2 cmol/kg and available P to about 30 mg/kg. These increases led to the 2.6 times increases in root volumes in the biochar amended soils over the un-amended counterpart. The fact that these root volumes 126 University of Ghana http://ugspace.ug.edu.gh are similar to those in the CaCO3 amended soils implies that the biochar types are equally effective as the conventional CaCO3 in promoting root development. Conventional lime amendment to Tikobo Series increased pH to 5.2 from 4.9 which resulted in reduction in Al saturation to 20%. Consequently, root volume increased from 1.45 cm3 to 3.33 cm3. On amendment with the biochar types, however, pH increased from 4.9 to between 5.7 and 6.2 with Al saturation reducing to undetectable levels. These translated into large root development accounting for root volume in the biochar amended Tikobo series increasing from 1.45 cm3 to between 3.89 and 5.99 cm3. A significant negative correlation coefficient of 0.747* between root volume and Al in solution of the two soils corroborates the assertion that as Al decreases, root volume increases. On liming with either CaCO3 or biochar, pH of Ankasa increased to between 4.7 and 5.2 with a corresponding increase in P availability from a paltry 1.54 mg/kg to between 12 mg/kg and 32 mg/kg. It thus appears that other factors such as pH and Al concentration are more important than P availability in root expansion especially in acid soils. The fact that when the synthetic P at the biochar P equivalent applied to the CaCO3 amended Ankasa Series gave statistically similar root volumes as when the soil was amended with biochar show that the P in the biochar was as effective as synthetic P for root development. The shoot dry matter of soya bean plants harvested from the un-amended Ankasa and Tikobo Series were relatively low i.e. 0.22 and 0.26 g, respectively, mainly because of their lower root volumes which hindered exploitation for nutrients. On amendment with CaCO3, shoot dry matter in Ankasa Series increased to 0.53 g as a result of an increase in root volume from 1.2 cm3 to 3.25 cm3. On amendment of biochar to the Ankasa and Tikobo Series, shoot dry matter also increased because of the liming effect which reduced Al saturation and hence increased root volume. A plot of shoot 127 University of Ghana http://ugspace.ug.edu.gh dry matter against root volume showed a positive correlation coefficient. Amending Tikobo with the biochar types also increased shoot dry matter to between 0.34 and 1.10 g. Table 5.1 shows the shoot to root ratio of soya bean plants harvested from the CaCO3 and biochar limed Ankasa and Tikobo Series. From the Table, it is clear that the plants from the Tikobo Series generally had higher shoot to root ratios than their counterparts from the Ankasa Series. The Ankasa Series having lower shoot to root ratio implies that P as a nutrient is relatively being channeled more into root development whilst the converse holds for the Tikobo Series. This might be a response of the plants to effect of presence of Al in the Ankasa soils. According to Martinez et al (2005) soya bean plants retain more phosphorus in their roots when under stress. This is corroborated by the relatively higher P uptake in roots than shoots of soya bean plants grown in Ankasa Series Tables 4.13. and 4.14. Addition of N to the limed soils irrespective of liming material increased shoot to root ratios indicating the effect of N in leaf production (Marschner, 1998) Addition of extra 30 kg P/ha from TSP to the biochar amended Tikobo Series did not increase root volume over that in the biochar amended soil implying that the P in the biochar was adequate for root expansion at the pH between 5.7 and 6.2 in the Tikobo Series. The extra P might have been used in producing heavier roots as corroborated by heavier root masses in the TSP fortified biochar amended Tikobo Series. This is also reflected in the higher root P uptake in the plants grown on the TSP-biochar amended Tikobo Series. The fact that on addition of TSP to the biochar amended Tikobo and Ankasa Series, only the RH700 treatment showed positive response of shoot dry matter to P could be an indication that the RH700 biochar type might be an ideal material for soya bean cultivation should inorganic fertilizer be 128 University of Ghana http://ugspace.ug.edu.gh Table 5. 1: Shoot to Root Dry Weight Ratio on Ankasa and Tikobo Series*. TREATMENTS ANKASA TIKOBO Un-amended 1.05d 1.86l LiN0P0 1.71k 0.75a LiN10P0 0.92bc 2.17o LiN0BEP 1.17ef 1.96m LiN10BEP 1.00d 0.95c CC500N0P0 0.83b 1.62j CC500N10P0 1.35h 1.55i CC700N0P0 1.13e 2.30p CC700N10P0 1.15e 1.11d RH500N0P0 1.21f 1.75k RH500N10P0 1.28g 1.89l RH700N0P0 0.69a 2.06n RH700N10P0 0.87b 1.29f CC500N0P30 1.69k 1.17e CC500N10P30 1.26fg 0.85b CC700N0P30 1.28g 0.94c CC700N10P30 1.56j 1.55i RH500N0P30 2.04l 1.14de RH500N10P30 1.13e 0.97c RH700N0P30 1.48i 0.83b RH700N10P30 1.50ij 1.42g CV (%) 2.8 *CC500= corn cob biochar at 500 oC, CC700= corn cob biochar at 700 oC, RH500= rice husk biochar at 500 oC, rice husk biochar at 500 oC, P= phosphorus, N= nitrogen, BEP = biochar equivalent phosphorus, Li= agricultural lime. Means with the same alphabet are not significantly (p>0.05) different. 129 University of Ghana http://ugspace.ug.edu.gh supplemented. This is further supported by the fact that it is only the RH700 that increased in shoot dry matter over its unfertilized counterpart upon addition of both synthetic N and P. 5.6. Liming and P Availability on Nodulation Nodulation of soya bean occurred only in Tikobo Series. As shown in Figure 1, the pH of Ankasa series rose to 5.2 after the incubation with the liming materials. Ideal pH for soya bean growth and nodulation is near neutral. Therefore, pH of 5.2 will hinder nodulation in Ankasa Series. The fact that no nodules were found in plants grown in the Ankasa Series even though upon liming available P concentration had been increased from 1.54 mg/kg to a minimum of 12 mg/kg and residual available P in the soil was between 13 and 22 mg/kg (Table 4.15) confirms the assertion that pH and Al saturation are more important in nodulation and root development of legumes than P availability (Angle, 1998; Giller et al., 1998). Nodules formed in Tikobo Series could be attributed to the increase in the soils’ pH as reflected at the end of the incubation period with values between 5.7 and 6.2. These increases in pH as already discussed led to reduction in Al concentration to undetectable levels promoting nodulation in the biochar amended Tikobo series. The RH700 proved to be yet a superior amendment for soya bean nodulation as without external P supplementation, it was the only amendment which produced soya bean with nodules. The four biochar types all had similar available P concentrations of between 2162 mg/kg and 2378 mg/kg. On addition of extra 30 kg P/ha from TSP, there was suppression of nodulation in the RH700 amended Tikobo Series whilst the other three biochar types which hitherto could not produce plants with nodules had soya bean plants nodulating. The residual analyses showed that 130 University of Ghana http://ugspace.ug.edu.gh all the unfertilized biochar pots had available P ranging between 13.5 mg/kg and 26 mg/kg. It thus appears that factors other than pH, Al concentration in solution and available P studied might be involved in nodulation. Factors such as Mo concentration, microbial population and diversity, nitrogenase as an enzyme (Alexander, 1977) which had not been investigated in this study and addition of urea could be playing major roles in nodulation. Nodule numbers in the RH700 reduced to seven upon urea fertilization at 10 kg/ha showing the negative effect of readily available N addition to nodulation (Alexander, 1977). Inexplicably the additional N caused nodulation in the CC700 biochar amended soil when urea was added. 5.7. Residual Nutrients To assess the effectiveness of the liming materials on P availability, the Apparent P Recovery Efficiency (APRE) was calculated according to the formula by Baligar, et al. (2007) 𝑁𝑢𝑡𝑟𝑖𝑒𝑛𝑡 𝑢𝑝𝑡𝑎𝑘𝑒,𝐹 (𝑚𝑔)−𝑁𝑢𝑡𝑟𝑖𝑒𝑛𝑡 𝑢𝑝𝑡𝑎𝑘𝑒 𝐶(𝑚𝑔)×100 APRE = [5.1] 𝑄𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑛𝑢𝑡𝑟𝑖𝑒𝑛𝑡 𝑎𝑝𝑝𝑙𝑖𝑒𝑑 (𝑚𝑔) Where F = Uptake in soil at specific P application rate and C = Uptake in un-amended soil The APRE shows the ability of the plant to obtain P as a nutrient from the soil (Baligar, et al. ,2007). In calculating the APRE, the average equivalent available P (BEP) in 80 Mg/ha of biochar applied per pot was used as the amount of P added. This translated to 220 mg P per pot for both biochar and TSP as BEP. The APRE of the various fertilized amendments are shown in Table 5.1. The APRE in the two soils were generally very low and below 12% and this is corroborated by the 131 University of Ghana http://ugspace.ug.edu.gh Table 5. 2: Apparent Phosphorus Recovery Efficiency in Ankasa and Tikobo Series* -------------EFFICIENCY (%)------------ TREATMENT ANKASA TIKOBO LiN0BEP 2.01 5.25 CC500N0P0 1.68 2.87 CC700N0P0 1.77 5.78 RH500N0P0 2.35 8.4 RH700N0P0 1.81 6.58 CC500N0P30 3.51 7.88 CC700N0P30 3.53 5.83 RH500N0P30 5.00 7.67 RH700N0P30 6.72 6.76 LiN10BEP 2.92 4.55 CC500N10P0 2.69 5.17 CC700N10P0 3.65 5.25 RH500N10P0 3.31 7.8 RH700N10P0 4.55 7.47 CC500N10P30 4.34 9.09 CC700N10P30 5.19 8.73 RH500N10P30 4.95 8.75 RH700N10P30 4.84 11.67 *CC500= corn cob biochar at 500 oC, CC700= corn cob biochar at 700 oC, RH500= rice husk biochar at 500 oC, rice husk biochar at 500 oC, P= phosphorus, N= nitrogen, BEP = biochar equivalent phosphorus, Li= agricultural lime 132 University of Ghana http://ugspace.ug.edu.gh higher residual total and available P in the soils after harvest. The Ankasa and Tikobo Series had initial total P contents of 164.0 mg/kg and 101.4 mg/kg, respectively. The residual P in the Ankasa Series was between 264.3 and 344.9 mg/kg and the Tikobo to between 170 and 257.8 mg/kg when the two soils were each amended with either biochar or CaCO3 plus biochar equivalent P (BEP) from TSP i.e. LiNoBEP. This high residual P from that of their initial especially from Ankasa shows that most of the added P had been transformed or fixed into non available total P. The Ankasa series being an Oxisol has a very low pH of 4.2 and is high in soluble Al concentration (0.15cmol/kg - 0.55 cmol/kg) coupled with its relatively high sesquioxidic and kaolinite content, it stands to reason that added P recovery is low. Recoveries were slightly higher in the Tikobo Series because of its relatively higher pH and undetectable levels of Al. It is worthy of note that particularly in the biochar amended Tikobo Series with no form of synthetic P input, plants grown from the RH biochar types recovered more P. Recoveries from Tikobo Series were generally higher in the biochar amended than the CaCO3 counterpart whilst the converse is true for the Ankasa Series. The biochar amended soils generally had higher residual available P and this holds promise for subsequent crop cultivation. The biochar with their inherently high total carbon enhanced the organic carbon contents of the residual soil. The TC in the Ankasa series which was initially 15.3 g/kg had increased to 31.73 to 52.79 g/kg showing between 1.64% and 3.74% addition of organic carbon (Table 4.15) when amended with the four biochar types. The Tikobo series on the other hand, showed between 1.35% and 1.52% addition of organic carbon. The over 1% increase in organic carbon content in the Tikobo Series should improve on the physical properties of the soil considering its inherent high sand content. It also affirms the use of biochar in sequestration of atmospheric C into soil. 133 University of Ghana http://ugspace.ug.edu.gh CHAPTER SIX 6 CONCLUSIONS AND RECOMMENDATION Conclusions The study has shown that anaerobic charring of rice husk at 500 oC and 700 oC produces biochar types with pH in water of 7.6 and 8.8, respectively. Charring of corn cob at the same temperatures produced biochar with pH in water of 10.7 and 11, respectively. Charring the two feedstocks at the two temperatures produced biochar with high concentrations of available P which could be exploited for use as fertilizer in crop cultivation. Corn cob biochar types sequester more carbon than the rice husk biochar types. The study has revealed that the four biochar types were superior to conventional liming material i.e. CaCO3 in liming Ankasa Series and Tikobo Series and therefore could be used as substitute for conventional agricultural lime. Amending the soils with corn cob and rice husk biochar as liming materials resulted in significant increase in root volume, root and shoot dry matter in typical acid soils of Ghana. Nitrogen and P uptake can be enhanced by amending acid soils of Ghana with rice husk and corn cob biochar types charred at 500 and 700 oC. Corn cob and rice husk biochar could be used as P source for growth of soya bean especially in Tikobo Series. Apparent Phosphorus Recovery Efficiencies could be enhanced when soya bean grown on acid soils are fertilized with both biochar and synthetic P 134 University of Ghana http://ugspace.ug.edu.gh Recommendation In order to increase the pH of Ankasa series to 6 for soya bean production, it is recommended that the biochar application rate of corn cob and rice husk be increased above the 80 tonnes per hectare or char the materials at higher temperatures to liberate more basic cations for use. Farmers are advised to give at least a six-week equilibration period upon addition of biochar before planting. Further study on effect of the corn cob and rice husk biochar on growth and nodulation of soya bean in Tikobo Series should be conducted in the field to determine if similar results are attainable. Subsequent study on growth and nodulation of soya bean upon amendment of biochar to acid soils, should investigate the effect of Mo, microbial population and nitrogenase enzyme on nodulation. It is also recommended that different feedstocks such as cocoa pods which may have higher levels of Ca and Mg be used as liming materials in a bid to reduce the application rate. Further work should also be carried out to determine how long the liming effect of the biochar types used in the experiment would persist in the soils. It is also recommended for cost benefit analysis to be done for the use of the biochar types in place of the conventional lime and inorganic P fertilizer vis-à- vis yield. 135 University of Ghana http://ugspace.ug.edu.gh REFERENCE Abekoe, M. K., & Sahrawat, K. L. 2001. Phosphate retention and extractability in soils of the humid zone in West Africa. Geoderma, 102(1), 175-187. Addo-Quaye, A. A., Saah, M. K., Tachie-Menson, C. K. B., Adam, I., Tetteh, J. P., Rockson- Akorly, V. K. & Kitson, J. E. 1993. General Agriculture for Senior Secondary Schools. MOE. 191-194. Adu-Dapaah, H. K., Asafo-Adjei, B., Owusu-Akyaw, M., & Amoah, S. 2004. 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Feedstock 5 354.2105 70.8421 77.98 <.001 Nitrogen 0 (1) 0.0263 Phosphorus 1 194.5268 194.5268 214.14 <.001 Soil 1 256.2115 256.2115 282.04 <.001 Nitrogen.Phosphorus 0 (1) 0.0355 Feedstock.Soil 5 215.8260 43.1652 47.52 <.001 Nitrogen.Soil 0 (1) 0.0008 Phosphorus.Soil 1 6.1865 6.1865 6.81 0.016 Nitrogen.Phosphorus.Soil 0 (1) 0.0012 Residual 22 (14) 19.9854 0.9084 Total 35 (18) 863.6172 Analysis of variance for total N g/kg ________________________________________________________________________ Source of variation d.f. (m.v.) s.s. m.s. v.r. F pr. ------------------------------------------------------------------------------------------------------------ Feedstock 5 4.89818 0.97964 93.85 <.001 Nitrogen 1 0.05733 0.05733 5.49 0.021 Phosphorus 1 0.00220 0.00220 0.21 0.647 Soil 1 24.35210 24.35210 2332.99 <.001 Feedstock.Nitrogen 4 (1) 0.09006 0.02252 2.16 0.078 Feedstock.Phosphorus 4 (1) 0.02643 0.00661 0.63 0.640 Nitrogen.Phosphorus 1 0.02323 0.02323 2.23 0.138 Feedstock.Soil 5 0.33607 0.06721 6.44 <.001 Nitrogen.Soil 1 0.00867 0.00867 0.83 0.364 Phosphorus.Soil 1 0.00470 0.00470 0.45 0.504 Feedstock.Nitrogen.Phosphorus 4 (1) 0.02022 0.00506 0.48 0.747 Feedstock.Nitrogen.Soil 4 (1) 0.06733 0.01683 1.61 0.175 Feedstock.Phosphorus.Soil 4 (1) 0.05438 0.01360 1.30 0.273 Nitrogen.Phosphorus.Soil 1 0.04003 0.04003 3.83 0.052 Feedstock.Nitrogen.Phosphorus.Soil 4 (1) 0.00695 0.00174 0.17 0.955 Residual 125 (19) 1.30477 0.01044 Total 166 (25) 28.61164 172 University of Ghana http://ugspace.ug.edu.gh Analysis of variance for Organic_C_g_kg _____________________________________________________________________________ Source of variation d.f. (m.v.) s.s. m.s. v.r. F pr. --------------------------------------------------------------------------------------------------------------------- ------------ FEEDSTOCK 5 14507.023 2901.405 513.63 <.001 NITROGEN 1 5.117 5.117 0.91 0.343 PHOSPHORUS 1 0.965 0.965 0.17 0.680 SOIL 1 11866.552 11866.552 2100.73 <.001 FEEDSTOCK.NITROGEN 4 (1) 55.413 13.853 2.45 0.049 FEEDSTOCK.PHOSPHORUS 4 (1) 56.516 14.129 2.50 0.046 NITROGEN.PHOSPHORUS 1 49.987 49.987 8.85 0.004 FEEDSTOCK.SOIL 5 1881.242 376.248 66.61 <.001 NITROGEN.SOIL 1 3.337 3.337 0.59 0.444 PHOSPHORUS.SOIL 1 0.034 0.034 0.01 0.938 FEEDSTOCK.NITROGEN.PHOSPHORUS 4 (1) 232.463 58.116 10.29 <.001 FEEDSTOCK.NITROGEN.SOIL 4 (1) 88.420 22.105 3.91 0.005 FEEDSTOCK.PHOSPHORUS.SOIL 4 (1) 139.405 34.851 6.17 <.001 NITROGEN.PHOSPHORUS.SOIL 1 46.766 46.766 8.28 0.005 FEEDSTOCK.NITROGEN.PHOSPHORUS.SOIL 4 (1) 104.226 26.057 4.61 0.002 Residual 123 (21) 694.799 5.649 Total 164 (27) 24310.923 _____________________________________________________________________________ 173 University of Ghana http://ugspace.ug.edu.gh Analysis of variance for root volume __________________________________________________________________________ Source of variation d.f. (m.v.) s.s. m.s. v.r. F pr. --------------------------------------------------------------------------------------------------------------------- ------------ FEEDSTOCK 5 110.9448 22.1890 60.99 <.001 NITROGEN 1 0.0005 0.0005 0.00 0.970 PHOSPHORUS 1 4.1375 4.1375 11.37 <.001 SOIL 1 67.4821 67.4821 185.49 <.001 FEEDSTOCK.NITROGEN 4 (1) 5.7466 1.4367 3.95 0.005 FEEDSTOCK.PHOSPHORUS 4 (1) 12.7160 3.1790 8.74 <.001 NITROGEN.PHOSPHORUS 1 2.1984 2.1984 6.04 0.015 FEEDSTOCK.SOIL 5 23.3974 4.6795 12.86 <.001 NITROGEN.SOIL 1 0.0887 0.0887 0.24 0.622 PHOSPHORUS.SOIL 1 0.4741 0.4741 1.30 0.256 FEEDSTOCK.NITROGEN.PHOSPHORUS 4 (1) 7.4897 1.8724 5.15 <.001 FEEDSTOCK.NITROGEN.SOIL 4 (1) 3.2262 0.8065 2.22 0.071 FEEDSTOCK.PHOSPHORUS.SOIL 4 (1) 6.1324 1.5331 4.21 0.003 NITROGEN.PHOSPHORUS.SOIL 1 0.0670 0.0670 0.18 0.669 FEEDSTOCK.NITROGEN.PHOSPHORUS.SOIL 4 (1) 9.3447 2.3362 6.42 <.001 Residual 126 (18) 45.8394 0.3638 Total 167 (24) 246.5300 _____________________________________________________________________________ 174 University of Ghana http://ugspace.ug.edu.gh Analysis of variance for_root_P_uptake ________________________________________________________________________ Source of variation d.f. (m.v.) s.s. m.s. v.r. F pr. ------------------------------------------------------------------------------------------------------------ FEEDSTOCK 5 1614.686 322.937 287.01 <.001 NITROGEN 1 87.704 87.704 77.95 <.001 PHOSPHORUS 1 422.781 422.781 375.75 <.001 SOIL 1 608.400 608.400 540.71 <.001 FEEDSTOCK.NITROGEN 4 (1) 143.825 35.956 31.96 <.001 FEEDSTOCK.PHOSPHORUS 4 (1) 342.349 85.587 76.07 <.001 NITROGEN.PHOSPHORUS 1 7.840 7.840 6.97 0.009 FEEDSTOCK.SOIL 5 205.441 41.088 36.52 <.001 NITROGEN.SOIL 1 2.996 2.996 2.66 0.105 PHOSPHORUS.SOIL 1 488.496 488.496 434.15 <.001 FEEDSTOCK.NITROGEN.PHOSPHORUS 4 (1) 505.605 126.401 112.34 <.001 FEEDSTOCK.NITROGEN.SOIL 4 (1) 288.652 72.163 64.13 <.001 FEEDSTOCK.PHOSPHORUS.SOIL 4 (1) 235.836 58.959 52.40 <.001 NITROGEN.PHOSPHORUS.SOIL 1 77.736 77.736 69.09 <.001 FEEDSTOCK.NITROGEN.PHOSPHORUS.SOIL 4 (1) 98.243 24.561 21.83 <.001 Residual 125 (19) 140.647 1.125 Total 166 (25) 4442.924 _______________________________________________________________________ 175 University of Ghana http://ugspace.ug.edu.gh Analysis of variance for shoot P uptake ________________________________________________________________ Source of variation d.f. (m.v.) s.s. m.s. v.r. F pr. --------------------------------------------------------------------------------------------------------------------- ------------ FEEDSTOCK 5 932.976 186.595 55.96 <.001 NITROGEN 1 244.332 244.332 73.28 <.001 PHOSPHORUS 1 437.104 437.104 131.10 <.001 SOIL 1 886.093 886.093 265.76 <.001 FEEDSTOCK.NITROGEN 4 (1) 101.408 25.352 7.60 <.001 FEEDSTOCK.PHOSPHORUS 4 (1) 351.897 87.974 26.39 <.001 NITROGEN.PHOSPHORUS 1 5.456 5.456 1.64 0.204 FEEDSTOCK.SOIL 5 152.536 30.507 9.15 <.001 NITROGEN.SOIL 1 8.343 8.343 2.50 0.117 PHOSPHORUS.SOIL 1 0.844 0.844 0.25 0.616 FEEDSTOCK.NITROGEN.PHOSPHORUS 4 (1) 26.829 6.707 2.01 0.100 FEEDSTOCK.NITROGEN.SOIL 4 (1) 47.139 11.785 3.53 0.010 FEEDSTOCK.PHOSPHORUS.SOIL 4 (1) 85.470 21.368 6.41 <.001 NITROGEN.PHOSPHORUS.SOIL 1 59.718 59.718 17.91 <.001 FEEDSTOCK.NITROGEN.PHOSPHORUS.SOIL 4 (1) 136.547 34.137 10.24 <.001 Residual 85 (12) 283.404 3.334 Total 126 (18) 3402.247 _____________________________________________________________________________ 176