Browsing by Author "Jones, J.W."
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Item Can ENSO help in agricultural decision-making in Ghana?(Climate Prediction and Agriculture: Advances and Challenges, 2007-01) Adiku, S.G.K.; Mawunya, F.D.; Jones, J.W.; Yangyouru, M.Rainfall variability has become a major agricultural issue in sub-Saharan Africa, especially since crop production is mainly rainfed. Irrigation technologies are expensive and their implementation is slow. Many researchers now believe that some understanding of the causes of rainfall variability would lead to measures that could be used to investigate reduction in total rainfall and/or drought effects. © 2007 Springer-Verlag Berlin Heidelberg.Item Climate Prediction and Agriculture Advances and Challenges, edited by Mannava V. K. Sivakurnar and James Hansen. In: Chapter 20; "Can ENSO help in agricultural decisionmaking in Ghana?" - Berlin Heidelberg(Springer Berlin Heidelberg, pp. 205-212, 2007) Yangyuoru, M.; Adiku, S.G.K.; Mawunya, F.D.; Jones, J.W.Rainfall variability has become a major agricultural issue in Sub-Saharan Africa, especially since crop production is mainly rainfed. Irrigation technologies are expensive and their implementation is slow. Many researchers now believe that some understanding of the causes of rainfall variability would lead to measures that could be used to investigate reduction in total rainfall and/or drought effects.Item Effects of crop rotation and fallow residue management on maize growth, yield and soil carbon in a savannah-forest transition zone of Ghana(Journal of Agricultural Science, 2009-02) Adiku, S.G.K.; Jones, J.W.; Kumaga, F.K.; Tonyigah, A.The purpose of the present study was to investigate the effects of seven maize (Zea mays)fallow rotation and fallow residue management treatments on growth, maize yield and soil carbon within a savannah-forest farming zone of Ghana. Over a 4-year period, maize rotated with bare fallow (control) produced an average maize biomass and yield of 4.0 and 1.0 t/ha/yr, respectively. Maize rotated with elephant grass (Pennisetum purpureum) with the fallow grass residue burning produced an average maize biomass and yield of 8.0 and 2.0 t/ha/yr, respectively. The removal of the fallow grass biomass (9.0 t/ha/yr) by burning resulted in a low total residue (maize stover+fallow residue) returned to the soil (7.0 t/ha/yr). The total residue returned to the soil was 14.0 t/ha/yr. Despite the larger total residue returned to the soil by the incorporation treatment, the performance of the maize was not significantly different from that of the fallow residue burning treatment. Maize rotated with cowpea (Vigna unguiculata), mucuna (Mucuna pruriens) or pigeon pea (Cajanus cajan) produced similar maize biomass of 8.0 t/ha/yr and yields of 2.0 t/ha/yr, but with higher variability for the maizecowpea rotation. Biomass produced by fallow cowpea, mucuna or pigeon pea were 4.0, 5.0 and 8.0 t/ha/yr, respectively, and total residues added to the soil were 13.0, 13.0 and 15.0 t/ha/yr, respectively. Maizegrass rotation with fertilizer application to the maize resulted in biomass and yield production of 11.0 and 3.0 t/ha/yr, respectively, and fallow grass production of 12.0 t/ha/yr. The total residue returned to the soil was 18.0 t/ha/yr. Soil organic carbon (SOC) declined under all treatments over time, with the control losing about 55% of the initial SOC by the end of the trial. The decline in SOC was 19% for the fertilized maizegrass rotation, but all other treatments lost between 33 and 44% SOC. Overall, the fertilized maizegrass and maizepigeon pea rotations were identified as those that sustained relatively high maize yields, returned large residue amounts to the soil and minimized soil carbon loss. © 2009 Copyright Cambridge University Press.Item Modeling soil and plant phosphorus within DSSAT(Ecological Modelling, 2010-11) Dzotsi, K.A.; Jones, J.W.; Adiku, S.G.K.; Naab, J.B.; Singh, U.; Porter, C.H.; Gijsman, A.J.The crop models in the Decision Support System for Agrotechnology Transfer (DSSAT) have served worldwide as a research tool for improving predictions of relationships between soil and plant nitrogen (N) and crop yield. However, without a phosphorus (P) simulation option, the applicability of the DSSAT crop models in P-deficient environments is limited. In this study, a soil-plant P model integrated to DSSAT was described, and results showing the ability of the model to mimic wide differences in maize responses to P in Ghana are presented as preliminary attempts to testing the model on highly weathered soils. The model simulates P transformations between soil inorganic labile, active and stable pools and soil organic microbial and stable pools. Plant growth is limited by P between two concentration thresholds that are species-specific optimum and minimum concentrations of P defined at different stages of plant growth. Phosphorus stress factors are computed to reduce photosynthesis, dry matter accumulation and dry matter partitioning. Testing on two highly weathered soils from Ghana over a wide range of N and P fertilizer application rates indicated that the P model achieved good predictability skill at one site (Kpeve) with a final grain yield root mean squared error (RMSE) of 535kgha-1and a final biomass RMSE of 507kgha-1. At the other site (Wa), the RMSE was 474kgha-1 for final grain yield and 1675kgha-1 for final biomass. A local sensitivity analysis indicated that under P-limiting conditions and no P fertilizer application, crop biomass, grain yield, and P uptake could be increased by over 0.10% due to organic P mineralization resulting from a 1% increase in organic carbon. It was also shown that the modeling philosophy that makes P in a root-free zone unavailable to plants resulted in a better agreement of simulated crop biomass and grain yield with field measurements. Because the complex soil P chemistry makes the availability of P to plants extremely variable, testing under a wider range of agro-ecological conditions is needed to complement the initial evaluation presented here, and extend the use of the DSSAT-P model to other P-deficient environments. © 2010 Elsevier B.V.Item 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.Item Simple formulation of the soil water effect on residue decomposition(Communications in Soil Science and Plant Analysis, 2010-02) Adiku, S.G.K.; Amon, N.K.; Jones, J.W.; Adjadeh, T.A.; Kumaga, F.K.; Dowuona, G.N.; Nartey, E.K.Soil water content, θ, is a major factor affecting residue decomposition, but simple formulation of this factor is often lacking. We observed that θ significantly (P < 0.001) affected the residue decomposition constant, kd· When θ varied from 0.09gg-1 to 0.23gg-1, kd ranged from 0.009 to 0.013d-1 and from 0.009 to 0.022d-1 for residues with carbon to nitrogen ratio (C/N) > 30 and C/N < 25, respectively. A θ factor was formulated in terms of the field capacity θFC and the air-dry θ d in the form fw = (θ - θd) / (θFC - θd), and this was used to modify the potential kd as θ varied. Coupling fw with a first-order residue decomposition equation resulted in the prediction of the decomposition of four residue types in the greenhouse (R2 = 0.94; relative root mean square error, RRMSE, = 0.06) and in the field (R2 = 0.93; RRMSE = 0.11). © Taylor & Francis Group, LLC.Item Tropical agricultural land management influences on soil microbial communities through its effect on soil organic carbon(Soil Biology and Biochemistry, 2013-10) Sul, W.J.; Asuming-Brempong, S.; Wang, Q.; Tourlousse, D.M.; Penton, C.R.; Deng, Y.; Rodrigues, J.L.M.; Adiku, S.G.K.; Jones, J.W.; Zhou, J.; Cole, J.R.; Tiedje, J.M.We analyzed the microbial community that developed after 4 years of testing different soil-crop management systems in the savannah-forest transition zone of Eastern Ghana where management systems can rapidly alter stored soil carbon as well as soil fertility. The agricultural managements were: (i) the local practice of fallow regrowth of native elephant grass (Pennis e tum purpureum) followed by biomass burning before planting maize in the spring, (ii) the same practice but without burning and the maize receiving mineral nitrogen fertilizer, (iii) a winter crop of a legume, pigeon pea (Cajanus cajan), followed by maize, (iv) vegetation free winter period (bare fallow) followed by maize, and (v) unmanaged elephant grass-shrub vegetation. The mean soil organic carbon (SOC) contents of the soils after 4 years were: 1.29, 1.67, 1.54, 0.80 and 1.34%, respectively, differences that should affect resources for the microbial community.From about 290,000 sequences obtained by pyrosequencing the SSU rRNA gene, canonical correspondence analysis showed that SOC was the most important factor that explained differences in microbial community structure among treatments. This analysis as well as phylogenetic ecological network construction indicated that members of the Acidobacteria GP4 and GP6 were more abundant in soils with relatively high SOC whereas Acidobacteria GP1, GP7, and Actinobacteria were more prevalent in soil with lower SOC. Burning of winter fallow vegetation led to an increase in Bacillales, especially those belonging to spore-forming genera. Of the managements, pigeon-pea cultivation during the winter period promoted a higher microbial diversity and also sequestered more SOC, presumably improving soil structure, fertility, and resiliency. © 2013 Elsevier Ltd.