Department of Soil Science

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Nodulation of legumes in inland valley soils of Ghana
(Symbiosis, 2000-01) Dogbe, W.; Fening, J.O.; Danso, S.K.A.
Because most African farmers cannot afford the purchase of chemical fertilizers to correct soil nutrient deficiencies, alternatives such as increased use of biological nitrogen fixation are most useful. For best results, sound recommendations are needed on the use of different legumes, their rhizobial requirement and management for optimum nitrogen fixation. In West Africa however, except for the highly popular legumes such as cowpea, soybean and groundnut, few reliable data are available on the abilities of other legumes to nodulate and fix nitrogen with naturally occurring strains of rhizobia in various soils and thus on the need for rhizobial inoculation. A screen-house study was conducted at the University of Ghana, Legon, to assess the potential of 13 commonly grown legumes in Ghana to form nodules with native rhizobia from eight inland valley soils and to identify those for which further research would be needed to enhance their nodulation. Two of the soils had indigenous rhizobia that induced formation of nodules on all the legumes evaluated. Rhizobia in the remaining soils induced the formation of nodules on more than 75% of the legumes studied. However, numbers of nodules plant-1 on most of the legumes were low and were influenced by (i) the type of soil, (ii) legume and (iii) the soil x legume interaction. Population densities of rhizobia capable of forming nodules with legumes in the studied soils estimated by the most probable number method (MPN) ranged from very low (negligible to 1.7 x 101 cells g-1 soil for those that could form nodules with mucuna) to high (up to 1.7 x 105 cells g-1 soil and 3.1 x 105 cells g-1 soil for cowpea and green gram, respectively). Nodule number per plant correlated significantly with some important indices of soil fertility; namely %N, available NO3 - and % organic C, with r values of 0.39*, 0.60* and 0.40*, respectively. Inoculation of mucuna increased nodulation by between 3 to 20-fold and N2 fixation by 18 to 98 percent depending on the soil type. Non-inoculated mucuna absorbed a high proportion of its N (up to 60%) from the soil and may mine the soil of native N if harvested for seed. The low rhizobial populations and poor nodulation are indications for the necessity for inoculating many of these legumes in similar soils in West Africa.
On the simulation of root water extraction: Examination of a minimum energy hypothesis
(Soil Science, 2000-03) Adiku, S.G.K.; Rose, C.W.; Braddock, R.D.; Ozier-Lafontaine, H.
An alternative procedure for calculating root water extraction from different depths of a soil profile is proposed. The procedure is based on the concept that the root water extraction entails energy expenditure by the plant and that the plant seeks to minimize the total rate of energy expenditure during water uptake. The model, therefore, considers root water extraction to be a minimization problem whose solution can be sought using a dynamic programming framework. We tested the model by simulating the variations of the soil water content using the time and depth of a maize-sorghum intercrop experiment reported for an 8-day drying cycle by Ozier-Lafontaine et al. (Plant and Soil 204:183-201, 1998). Simulated patterns follow the observed water content distribution quite well. Furthermore, results from numerical experiments show that the model is capable of simulating a range of water extraction patterns in a realistic manner. Patterns of water extraction from uniformly wet soil profiles follow those of the root distribution with depth. The extraction rate is highest in the section where the root length density is also highest. Once the soil profile dries out, water extraction patterns cease to bear any similarity to root distribution. Model simulations also show increased root activity at greater depths when the top sections of the soil dry out. Generally, the model avoids the need to make any prior assumptions about the pattern of the root water extraction.
Ameliorating acid infertile rice soil with organic residue from nitrogen fixing trees
(Nutrient Cycling in Agroecosystems, 2000-06) Baggie, I.; Zapata, F.; Sanginga, N.; Danso, S.K.A.
Residues from two nitrogen fixing trees, Albizia zygia and Gliricidia sepium and one non nitrogen fixing tree Samania dinklagei and their combination with 50% of rice husk, were evaluated for their effect on growth and yield of rice (Oryza sativa) varieties (Rok 10 and Rok 23) grown in an Oxisol collected from a rice paddy in Inland valley swamps of Sierra Leone, West Africa. Ground and dried residues were mixed with soil and labelled with N15 ammonium sulfate (9.855% atom excess) at a rate of 10 mg N kg-1 soil. The 32P isotopic exchange method was used to determine the effect of organic residue incorporation on the bioavailable soil P status at five levels of P application. Albizia zygia and G. sepium had higher quality leaf litter (with relatively lower C/N, lignin/N and cellulose/N ratios) whereas Semania dinklagei and rice husk had high carbon. lignin and polyphenolic contents. Application of organic residue had positive effects on the soil available P status at varying degrees. Higher adsorption capacity, kinetic value and mean solution time of phosphates in solution were obtained with the A. zygia, and G. sepium residues. These values were lower with rice husk and S. dinklagei. Gliricidia sepium and A. zygia contributed more nitrogen derived from organic residue than rice husk and S. dinklagei but the mixture of A. zygia and G. sepium with rice husk enhanced N utilization.
Simulation of the dry matter production and seed yield of common beans under varying soil water and salinity conditions
(Agricultural Water Management, 2001-02) Adiku, S.G.K.; Renger, M.; Wessolek, G.; Facklam, M.; Hecht-Bucholtz, C.
We present a model that simulates the effects of water and salinity stress on the growth of beans. The model derives a combined soil water/salinity stress factor from the total water potential (combination of the matric and the osmotic potentials) and uses this stress factor as a growth limiter in a growth model. The model was tested on data obtained from two greenhouse trials of beans (Phaseolus vulgaris) grown under a range of soil water and salinity conditions. The simulated dry weight of the bean generally followed those observed. In the first trial, the comparison between simulated and observed total dry weight and seed yield gave R2 values of 0.97 and 0.92, respectively. Comparison of the simulated to the observed dry weight for the second trial gave R2 values of 0.85 and 0.89, respectively. These indicate a good performance of the model in general. The principle of deriving a combined water/salinity stress from the matric and osmotic potentials is simple and can be included as a simple routine in many existing crop models without much difficulty. © 2001 Elsevier Science B.V.
Conceptual methodologies in agro-environmental systems
(Soil and Tillage Research, 2001-03) Rose, C.W.; Adiku, S.
When continuous measurement of relevant above- and below-ground environmental factors is made, and the dynamics of crop growth and phenology is followed, it is shown that small-plot agronomic experimentation can provide information vital to the development and testing of simulation models. Such models for crops of maize (Zea mays) and the legume cowpea (Vigna unguiculata), grown as sole crops and in an intercrop system, were used to simulate yield at two separate sites in the main savanna farming zones in Ghana, West Africa. Simulation was carried out for these three cropping systems using 20 years of historical rainfall data for the two sites, investigating the effect on yield of management options which included time of planting, rate of nitrogen fertilizer application, and crop planting density. The yield results of this series of simulations were then subject to two different types of analysis in order to assist the evaluation of agricultural options for the nation. The first analysis was an economic evaluation based on gross margins, but using the stochastic-dominance technique to rank the profitability of the alternative cropping and management systems. The second, more general methodology employed was multi-criteria analysis (MCA). This analysis covered economic returns and their variability, the amount and quality of residue returned to the soil, and the aerial cover provided by the crop. Other factors which could affect the sustainability of production in the long term, but which could only be evaluated qualitatively, were also included in the analysis, as allowed in MCA methodology. The MCA was then carried out for three scenarios in which different weightings were given to economic outcomes and to factors which are believed to encourage ecological sustainability. These scenarios allow recognition of different priorities which might be given by traditional subsistence farmers as compared to commercial producers. Outcomes of this broad analysis of development alternatives provided scientific support for the traditional Ghanaian practice of grain/legume intercropping which is also widespread in the tropics. The suite of methodologies illustrated by the case study appears to be suitable for the evaluation of alternative farming systems at the scale of a small nation such as Ghana. © 2001 Elsevier Science B.V.
Phosphate retention and extractability in soils of the humid zone in West Africa
(Geoderma, 2001-07) Abekoe, M.K.; Sahrawat, K.L.
Phosphate adsorption and desorption studies provide insight for developing P management strategies. Very few studies have concentrated on P desorption which provides information on the reversibility of adsorbed P. Phosphate adsorption and desorption studies were carried out on seven rice-growing soils from three countries in West Africa, with the objective of relating these processes to P management strategies for the soils. The standard P requirement (SPR) of soils, defined as the amount of P to be added to attain an equilibrium solution concentration of 0.2 mg P 1-1, varied from 42 to 175 mg P kg-1. Out of the seven soils, four required low amounts and the other three needed relatively higher P applications. The extractability of the adsorbed P in different extractants was: 0.01 M KCl 32-78%, Olsen P 21-112%, and Bray 1 P 15-40%. Differences in the amounts of P desorbed by the soils suggested that the critical P levels needed for P management must be different. Management options to increase P availability in the soils are suggested. © 2001 Elsevier Science B.V.
Patterns of root growth and water uptake of a maize-cowpea mixture grown under greenhouse conditions
(Plant and Soil, 2001-08) Adiku, S.G.K.; Ozier-Lafontaine, H.; Bajazet, T.
This study investigated the patterns of root growth and water uptake of maize (Zea mays L.) and cowpea (Vigna unguiculata (L.) Walp) grown in a mixture under greenhouse conditions. The plants were grown in root boxes for 5 weeks under 2 watering regimes; fully irrigated and water stress conditions, followed by a 5-day drying cycle imposed during the 6th week of growth. Water uptake patterns were analysed during the drying cycle. The two-dimensional distribution of the roots of both plants in the boxes was determined immediately at the end of the drying cycle. Under well-irrigated conditions, the roots of the component plants grew profusely into all sections of the root box and intermingled considerably. Water stress resulted in the decline of root growth of maize and cowpea but the root:shoot ratios of maize and cowpea were not affected, suggesting that there was no significant effect of water stress on root:shoot partitioning. However, water stress affected the biomass distribution between fine and coarse roots in cowpea. About 64% by weight of cowpea roots under water stress were coarse whereas as against 48% under well-irrigated conditions. Furthermore, water stress generally restricted the lateral extent of the roots of both maize and cowpea with a tendency of clumping together of the root systems and a reduced degree of intermingling. Thus, the extent of mixing of the root systems was apparently controlled by the availability of soil water. Water uptake from the well-irrigated soil in the root boxes was initially restricted to the sections directly below the base of each plant. Although roots of both plants were present in almost all sections of the root box, all the sections did not contribute simultaneously to water uptake by each plant. Water uptake was delayed from the middle intermingled zones. In effect, uptake patterns did not relate generally to the root distribution. The tendency was for the component plants to initially 'avoid' water uptake from zones of intense intermingling or competition.
Farming system-induced variability of some soil properties in a sub-humid zone of Ghana
(Plant and Soil, 2001-09) Atsivor, L.; Dowuona, G.N.; Adiku, S.G.K.
This study assessed the effects of different farming systems, namely woodlot (WL), alley farming (AL), conventional tillage (CT) and natural fallow (NF) on the variability of organic carbon (OC) content and mean weight diameter (MWD) of a degraded Ferric Acrisol in the sub-humid zone of Ghana. The soils under woodlot accumulated the highest amount of organic carbon (18.6 g kg-1) with the least spatial variability apparently due to the greater additions of litter and minimum tillage. The conventionally tilled soil had the least OC content (13.1 g kg-1). Similar to the OC content, the woodlot soils also had the highest aggregate stability (MWD = 1.78 mm) and the least spatial variability. The stability of soil aggregates under the farming systems was greatly influenced by OC content; there was a good correlation between OC and MWD (r > 0.62**). Correlograms showed that OC and MWD are space dependent. The correlation length for OC under the different farming systems followed the order WL > NF > AL > CT, indicating that WL ensured a greater uniform distribution soil organic matter. The spatial distribution in MWD followed the same trend observed for OC. The MWD in the other farming systems was poorly related from point to point with shorter k-values, suggesting lack of uniformity due to low accumulation of OC. Generally, the woodlot system appeared to be a better, low-input restorer of soil productivity.
Comparison of greenhouse and 32P isotopic laboratory methods for evaluating the agronomic effectiveness of natural and modified rock phosphates in some acid soils of Ghana
(Nutrient Cycling in Agroecosystems, 2002-05) Owusu-Bennoah, E.; Zapata, F.; Fardeau, J.C.
Phosphorus deficiency is one of the major constraints for normal plant growth and crop yields in the acid soils of Ghana and therefore addition of P inputs is required for sustainable crop production. This is often difficult, if not impossible for small-scale farmers due to the high cost of mineral P fertilizers and limited access to fertilizer supplies. Direct application of finely ground phosphate rocks (PRs) and their modified forms have been recommended as alternatives for P fertilization. The direct application of the natural and modified PRs to these acid soils implies the need to predict their agronomic effectiveness of the PRs in the simplest and most cost-effective manner. In this study the classical greenhouse pot experiment was compared to the 32P isotopic kinetics laboratory method for evaluating the agronomic effectiveness of natural and modified Togo PR in six highly weathered Oxisols from southwest Ghana. In the 32P isotopic kinetics laboratory experiment the six soil samples were each fertilised at the rate of 50 mg P kg-1 soil in the form of triple superphosphate (TSP), Togo PAPR-50%, and Togo PR, respectively. Controls without P amendment were also included. Isotopic exchange kinetics experiments were carried out on two sets of samples, immediately after P fertilizer additions (without incubation) and after 6 weeks of incubation under wet conditions and at a room temperature of 25 °C. In the greenhouse pot experiment, P fertilizers in the form of Togo PR, Togo PAPR, Mali PR and TSP were each applied to the six soils at rates equivalent to 0, 30, 60, and 120 kg P ha-1, respectively. The P fertilizers were mixed with the soils and maize (Zea mays L.) variety Obatanpa was grown for 42 days before harvest. The isotopic kinetics data of the control samples indicated that 5 of the studied soils had very low P fertility status as reflected by their low P concentrations in solution (CP<0.02 mg P 1-1) and low exchangeable P (E1min < 5 mg P kg-1). The capacity factor and the fixation index of the soils were variable. Application of water-soluble P as TSP increased both the CP and E1 values of all the soils above the critical levels. Togo PR was least effective among the fertilizers tested for all soil soils, except in Boi soil. Acidulation of Togo PR (Togo PAPR-50%) was an effective means to increase its agronomic effectiveness. Direct application of natural Togo PR would be only feasible in the Boi soil series as reflected by its high Pdff% value in soil solution. Incubation with the P fertilizers caused an increase in the soil pH and a decline in the effectiveness of the applied P fertilizers, irrespective of the soil and the fertilizer utilized. Based upon the results of the greenhouse pot experiment, the relative crop response index (RCRI) in terms of increasing dry matter yield and P uptake followed the order of TSP > PAPR = Mali PR >Togo PR = Control. Both the laboratory index, Pdff% in soil solution derived from the isotopic method and the RCRI values obtained from the pot experiment produced similar results in ranking the P fertilizers tested according to their agronomic effectiveness. The isotopic kinetic method may be considered as an alternative to both greenhouse and field methods in the evaluation of agronomic effectiveness of P fertilizers in tropical acid soils when it offers comparative advantages in assessing the soil P status and its changes. But trained staff and adequate laboratory facilities are needed to perform this technique. Also the method can be used as a reference for comparison purposes as in this case. Further research is needed to assess the overall agronomic effectiveness (immediate and residual effects) of PR sources in predominant cropping systems of this region of Ghana.
Variation in symbiotic effectiveness of cowpea bradyrhizobia indigenous to Ghanaian soils
(Applied Soil Ecology, 2002-07) Fening, J.O.; Danso, S.K.A.
The potential for improving biological nitrogen fixation through rhizobial inoculation requires knowledge of the abundance and effectiveness of the indigenous rhizobia population in the soil. Cowpea bradyrhizobia in 20 soils in Ghana were enumerated and isolates from nodules of cowpea grown in these soils were examined in sand for symbiotic effectiveness. The 100 isolates examined varied greatly with estimated values for effectiveness, relative to an uninoculated control, ranging from 23.5 to 118%. The isolates thus ranged from ineffective to highly effective, but with most of them (68%) being ranked as moderately effective and with the highly effective ones constituting only 26% of the 100 isolates studied. The results obtained raise an important question, whether the 26% highly effective bradyrhizobia are capable of satisfying optimum N requirements from symbiotic N2 fixation. Diversity of the isolates in symbiotic effectiveness was again revealed when compared to the fertilized N control or with a standard strain of Bradyrhizobium sp. Some of the isolates had high N2 fixing capabilities that were comparable to the N fertilized plants with the equivalent of 70 kg/ha of inorganic N, with some of them showing superiority in symbiotic effectiveness relative to the standard strain. These data suggest that native isolates are a potentially useful source of strains for preparing highly effective cowpea inoculants. © 2002 Elsevier Science B.V. All rights reserved.
A phase analysis of season on the earth surface using GVIP data
(Advances in Space Research, 2002-11) Tanaka, S.; Sugimura, T.; Adjadeh, T.A.
October is the peak of fall in the middle latitude whereas August is the beginning of the season in the northern polar region. In the northern polar region, the peak of the infrared reflectance arrives at the beginning of August and it marks the onset of sleet. Thus, fall starts earlier in the northern polar region. However, the emergence of red-leaf is what is actually used as an index of fall. Reddening of leaves progresses from the north to the south. When fall is defined as the period in which leaf blossom is at its peak, then the period could be used to analyze the time of fall in the region. On the contrary, fall dose not occur in the tropical region. However, it is known that the tropics vegetation reaches full blossom a few weeks after the end of the rainy season. This time could be defmed as being equivalent to fall. Thus, our objective is to determine the time of fall all ove:r the world by making a phase analysis of a time, series of NOAA/AVHRR data. The first approach makes use of a method, which considers the date on which the channel 2 data records the peak value to be the date of fall. A global view of fall obtained by this method is presented. Progress of fall is indicated correctly in the eastern part of the Asian continent and the North American continent. The equivalent of fall in West Africa is discussed as representative of the season in the tropical region. © 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
Water surface area measurement of Lake Volta using SSM/I 37-GHz polarization difference in rainy season
(Advances in Space Research, 2002-11) Tanaka, M.; Adjadeh, T.A.; Tanaka, S.; Sugimura, T.
The objective of this study is to examine the possibility of measuring the area of Lake Volta using DMSP-SSMA data. In the method 1, using the difference between 37-GHz data of water surface and of the ambient land, stable values for three years in the rainy season are obtained. The difference between 37-GHz Vpol values and that of 37-GHz HPOl fluctuates slightly. Although we could not obtain the truth data due to cloud cover over the area in the rainy season, data obtained from NOAA/AVHRR and ETOPO5 elevation provide a means to evaluate the result from the SSM/I data. © 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
Long-term cropping effect on phosphorus fractions in an Ultisol of the humid forest zone in West Africa
(Communications in Soil Science and Plant Analysis, 2003-03) Abekoe, M.K.; Sahrawat, K.
The nature of phosphorus (P) pools in soils after application of P fertilizers should be considered when designing management practices to raise P fertility. Five rates of P: 0(P0), 45(P45), 90(P90), 135(P135) and 180(P180) kg ha-1 in the form of triple superphosphate (TSP) were applied once in 1993 on a Typic Paleudult at Man in Côte d'Iviore and the soil was cropped successively for five years (i.e., up to 1998) with four upland rice cultivators. At the end of the cropping season in 1998, soil samples were collected from the various P treated plots and the following P fractions were analyzed: resin-P, NaHCO3-Pi, NaOH-Pi, HCl-P residual P and organic P. The P fractions were compared with those of stored soil samples collected in the field before the initiation of the experiment in 1993. Five years of cropping the soil reduced labile Pi (resin-P + NaHCO3-Pi) from 10.8 mg P kg-1 in the uncultivated soil to 7.62mg P kg-1 in the control (P0) and to 9.71 mg kg-1 in the P45 treatment. Labile Pi in P90 was the same (10.7 mg P kg-1) as in the uncultivated soil but in the P135 and P180 soils, labile Pi increased by 1.3 and 2.7 mg P kg-1 above that of the uncultivated one. The NaOH-Pi and residual P fractions of lower availability increased with increasing rates of P application. The results suggested that on the Ultisol studied, P applied once to a field, cropped successively over a period of time was not an adequate management option. Frequent P application at low rates at each cropping season is suggested and merits investigation on the Ultisol studied.
Simplifying the analysis of soil particle sizes. I. Test of the Sur and Kukal's modified hydrometer method
(Communications in Soil Science and Plant Analysis, 2005-01) Adiku, S.G.K.; Osei, G.; Adjadeh, T.A.; Dowuona, G.N.
This study tests the validity of the Sur and Kukal modified hydrometer method for particle size analysis on eight Ghanaian soils of varying texture. The method assumes that hydrometer readings at any time could be predicted from an exponential equation provided that two important parameters are known: the 4.5-min hydrometer reading (R4.5) and the exponent (B). In a series of sedimentation experiments conducted on each soil in this study, 11 hydrometer readings were taken between 40 s and 8 h. Some of these data were used to determine the value of the parameters R4.5 and the exponent B. The B values for the light textured soils were within the range of 4.2 × 10 -3 to 9.7 × 10-3 and were comparatively lower than those for the heavy textured soils (1.0 × 10-2 to 1.5 × 10-2). In addition, the R4.5 values were much lower for the light textured soils than for the heavy textured soils. Using these parameter values in the Sur and Kukal's equation enabled the prediction of the hydrometer readings at different times during the sedimentation process. The predicted 8-h hydrometer reading also was used to calculate the percent clay. A comparison between the observed and predicted hydrometer readings was satisfactory. The predicted percent clay also agreed very well with that observed for all soils (R2 = 0.96). It is concluded that the Sur and Kukal method indeed simplifies the determination procedure and yields acceptable results for a wide range of Ghanaian soils.
Physiological and morphological responses to water stress in two Acacia species from contrasting habitats
(Tree Physiology, 2005-03) Otieno, D.O.; Schmidt, M.W.T.; Adiku, S.; Tenhunen, J.
Container-grown seedlings of Acacia tortilis Forsk. Hayne and A. xanthophloea Benth. were watered either every other day (well watered) or every 7 days (water-stressed) for 1 year in a greenhouse. Total plant dry mass (T dm), carbon allocation and water relations were measured monthly. Differences in leaf area (LA) accounted for differences in Tdm between the species, and between well-watered and water-stressed plants. Reduction in LA as a result of water stress was attributed to reduced leaf initiation, leaf growth rate and leaf size. When subjected to prolonged water stress, Acacia xanthophloea wilted more rapidly than A. tortilis and, unlike A. tortilis, lost both leaves and branches. These differences between species were attributed to differences in the allocation of carbon between leaves and roots and in the ability to adjust osmotically. Rapid recovery in A. xanthophloea following the prolonged water-stress treatment was attributed to high cell wall elasticity. Previous exposure to water stress contributed to water-stress resistance and improved recovery after stress. © 2005 Heron Publishing - Victoria, Canada.
Soil fertility status and potential organic inputs for improving small holder crop production in the interior savanna zone of Ghana
(Journal of Sustainable Agriculture, 2005-04) Fening, J.O.; Adjei-Gyapong, T.; Yeboah, E.; Ampontuah, E.O.; Quansah, G.; Danso, S.K.A.
Soil fertility decline is a major problem facing small-scale farming in Sub-Saharan Africa. To optimize the productivity of fertilizer usage, it is imperative that the fertility status of the soil is known. This study was conducted to evaluate the fertility status and potential organic inputs that can be used alone or in combination with mineral fertilizers for increased crop production in the interior savanna zone of Ghana. A survey of the availability of potential organic inputs in the region identified cow dung, refuse compost, and some plant residues with potential for enhancing soil productivity. Soil, household refuse, cow dung, and plant samples were collected from 40 farming communities and analyzed using standard protocols. The decomposition and nutrient release patterns of the organic materials were further investigated in laboratory incubation studies and in litter bags for 12 weeks. Results of the physico-chemical analysis revealed that soils in the interior savanna zone are coarse textured with low exchange capacity. The majority of the soils have low organic matter contents (1.0 ±0.4%) and low levels of the major plant nutrients. Available P in particular was very low with most of the soils having values less than 5.0 ppm. Elemental analysis of the materials revealed that they contained appreciable quantities of macro and micronutrients. The N contents of all the plant materials were higher than the critical level of 20.0-25.0 mg g-1 below which net N immobilization from the soil would be expected. The P contents of all the materials were above the critical level of 2.5 mg g-1 for P mineralization. The C/N ratios of all the materials were below 25, which indicate rapid mineral N release during decomposition. The decomposition of the materials indicated the high potential of the materials to supply NPK to crop plants within the experimental period. This suggests that the application of these materials to soil alone or in combination with mineral fertilizer ould improve nutrient availability to crop plants. Since results obtained may differ under field condition where mineralization tends to be complicated by environmental factors, field studies using a test crop such as maize are recommended to establish the relationship between nutrient release from the materials and crop demand. © 2005 by The Haworth Press, Inc. All rights reserved.
Time of planting Mucuna and Canavalia in an intercrop system with maize
(Journal of Agronomy, 2007-04) Innocent Lawson, Y.D.; Dzomeku, I.K.; Drisah, Y.J.
Field experiment was conducted to investigate the effects of two cover crops, Mucuna pruriens var. cocchinchinensis and Canavalia ensiformis, on weed interference and yield of maize (Zea mays var Okomasa) in an intercropping system at different planting dates. The cover crops were intercropped 0, 2, 4 and 6 Weeks After Planting Maize (WAPM). The intercrop components were sown at 80x40 cm and arranged in a 1:1 spatial arrangement. Non-intercropped maize plots served as sole maize or control. Results showed that Mucuna had better spreading ability than Canavalia. The highest cover spread for Mucuna and Canavalia was observed when they were intercropped at 4 and 2 WAPM, respectively. Results also showed that the two cover crops exhibited (more than 56%) weed suppression when intercropped at 4 WAPM. The highest weed suppression for Mucuna and Canavalia were recorded when they were planted at 4 and 0 WAPM, respectively. The grain yield of maize increased with delay in planting both cover crops (i.e., from 0 to 6 WAPM). The highest grain yield values of 2.95 t ha-1 for Mucuna and 2.56 t ha-1 for Canavalia entries were obtained when the cover crops were planted at 6 WAPM. These values however fell short of the sole maize (3.72 t ha-1) but were higher than the national average yield of 1.58 t ha-1 for the 2004 growing season. The present study therefore recommends that Mucuna pruriens var. cocchinchinensis and Canavalia ensiformis could be intercropped at 4 WAPM in maize-cover crop intercrop system with one early hand weeding for good maize grain yield. © 2007 Asian Network for Scientific Information.
Enhancing the agronomic effectiveness of natural phosphate rock with poultry manure: A way forward to sustainable crop production
(Nutrient Cycling in Agroecosystems, 2007-08) Agyin-Birikorang, S.; Abekoe, M.K.; Oladeji, O.O.
Phosphorus inputs are required in highly weathered tropical soils for sustainable crop production. However, high cost and limited access to mineral P fertilizers limit their use by resource-poor farmers in West Africa. Direct application of finely ground phosphate rock (PR) is a promising alternative but low solubility of PR hampers its use. Co-application of PR with manure could be a low cost means of improving the solubility of natural PR and improve their agronomic effectiveness. Our objective was to quantitatively estimate the enhancement effect of poultry manure on P availability from low reactive PR (Togo phosphate rock) applied to highly weathered soils. We utilized two highly weathered soils from Ghana and Brazil for this greenhouse study. Using 32P isotopic tracers, the agronomic effectiveness of poultry-manure-amended Togo rock phosphate (TPR) was compared with partially acidulated Togo rock phosphate (PAPR) and triple superphosphate (TSP). Four rates of poultry manure: 0, low (30 mg P kg-1 soil), high (60 mg P kg-1 soil) and very high (120 mg P kg-1 soil) were, respectively, added to a constant amendment (60 mg P kg-1 soil) of the P sources and applied to each pot of 4 kg soil. A Randomized Complete Block Design was used for the greenhouse experiment and Maize (Zea mays L.) was used as a test crop. The plants were grown for 42 days after which the above ground biomass was harvested for analysis. Without poultry manure addition, the agronomic effectiveness, represented by the relative agronomic effectiveness (RAE) and proportion of P derived from fertilizer (% Pdff) was in the order TSP > PAPR > TPR = control (P0). In the presence of low rate poultry manure addition, the agronomic effectiveness followed the order TSP > PAPR = PR > P0. However, at the high and very high rates of poultry manure addition, no significant differences in agronomic effectiveness were observed among the P sources, suggesting that at this rate of poultry manure addition, PR was equally as effective as TSP. The study showed that direct application of PR co-applied with poultry manure at a 1:1 P ratio will be a viable option for P replenishment. Thus a combination of PR and poultry manure could be a cost-effective means of ensuring sustainable agricultural production in P-deficient, highly weathered tropical soils. © 2007 Springer Science+Business Media B.V.
Genetic Variability in Micronutrients Composition of Orchardgrass (Dactylis glomerata L.)
(International Journal of Agricultural Research 8(2): 655-666, 2008) Hasinur-Rahman, M.; Adjadeh, T.A.; Saitoh, H.; Saiga, S.
In this study, it is hypothesized that plants selected and/or bred for improved desired characteristics (e.g., macronutrients) may affect other characteristics (e.g., micronutrients) negatively. To test the hypothesis, we evaluated the metal micronutrient concentrations of four experimental strains viz., HighMgE, HighMgM, LowEq and LowMg and two commercial cultivars viz., Okamidori and Akimidori of orchardgrass. There were no genetic differences among the experimental strains/cultivars of orchardgrass for dry matter accumulation. The concentration of micronutrients varied with genetic differences among the four strains and the two commercial cultivars of orchardgrass. The amounts of Mn, Fe, Zn, Cu, Mo, Co, Ni, Se and I in the shoot, irrespective of strain or cultivars used, were 76.36, 74.83, 14.03, 9.36, 2.19, 5.00, 5.17, 2.00 and 19.33 μg g-1 at first harvest and 85.89, 74.56, 15.06, 12.30, 3.84, 6.14, 4.99, 2.54 and 19.53 μg g-1 at second harvest, respectively. The average amounts at the third harvest were 119.97, 90.36, 17.67, 13.39, 3.36, 4.56, 4.89, 2.36 and 20.06 μg g-1, respectively, whereas the corresponding amounts at the fourth harvest were 128.22, 156.00, 21.92, 10.31, 4.25, 4.53, 4.54, 1.47 and 28.72 μg g-1, respectively. Apart from few exceptions, Mn, Fe, Zn, Mo and I levels were highest in the fourth harvest, whereas the levels of Co and Se were highest in the second harvest. The level of Cu was the highest in the third harvest. The levels of Mn, Fe, Ni, Se and Mo were higher in low Mg containing plants irrespective of strain or cultivar. On the other hand, Co, Cu and I tended to peak in plants containing higher amounts of Mg. The Cu/Mo ratio was highest in the first harvest followed by the third, second and fourth harvests. The amounts of Mn, Fe, Ni, Co, Zn and Mo were within the optimum levels required for maintaining forage quality.
Short-term effects of crop rotation, residue management, and soil water on carbon mineralization in a tropical cropping system
(Plant and Soil, 2008-10) Adiku, S.G.K.; Narh, S.; Jones, J.W.; Laryea, K.B.; Dowuona, G.N.
The purpose of this study was to investigate the short-term effects of maize (Zea mays)-fallow rotation, residue management, and soil water on carbon mineralization in a tropical cropping system in Ghana. After 15 months of the trial, maize-legume rotation treatments had significantly (P < 0.001) higher levels of potentially mineralizable carbon, C 0 (μg CO 2-C g-1) than maize-elephant grass (Pennisetum purpureum) rotations. The C 0 for maize-grass rotation treatments was significantly related to the biomass input (r = 0.95; P = 0.05), but that for the maize-legume rotation was not. The soil carbon mineralization rate constant, k (per day), was also significantly related to the rotation treatments (P < 0.001). The k values for maize-grass and maize-legume rotation treatments were 0.025 and 0.036 day-1 respectively. The initial carbon mineralization rate, m 0 (μg CO2-C g-1 day -1), was significantly (P < 0.001) related to the soil water content, θ. The m 0 ranged from 3.88 to 18.67 and from 2.30 to 15.35 μg CO2-C g-1 day-1 for maize-legume and maize-grass rotation treatments, respectively, when the soil water varied from 28% to 95% field capacity (FC). A simple soil water content (θ)-based factor, f w, formulated as: fw = [θ-θd/ θFC-θd], where θ d and θ FC were the air-dry and field capacity soil water content, respectively, adequately described the variation of the m 0 with respect to soil water (R 2 = 0.91; RMSE = 1.6). Such a simple relationship could be useful for SOC modeling under variable soil water conditions. © 2008 Springer Science+Business Media B.V.

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