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Dzotsi K.A.,University of Florida | Dzotsi K.A.,British Petroleum | Jones J.W.,University of Florida | Adiku S.G.K.,University of Florida | And 6 more authors.
Ecological Modelling | Year: 2010

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.

Bidogeza J.C.,International Center for Soil Fertility and Agricultural Development | Bidogeza J.C.,Wageningen University | Hoogenboom G.,Washington State University | Berensten P.B.M.,Wageningen University | And 2 more authors.
Journal of Crop Improvement | Year: 2012

The low agricultural productivity of Rwanda reflects the poor soil fertility status caused by a low organic matter and high soil acidity that characterizes a large part of the country. Experimental trials have shown that a combined use of organic and inorganic fertilizers can increase crop yield. However, there are no guidelines for combined nutrients of different sources and qualities. Crop growth models can assist in the evaluation of the integration of organic and inorganic fertilizers. The Decision Support System for Agrotechnology Transfer (DSSAT) presents a collection of such crop models. The objective of this study was to determine alternative production activities through yield prediction of several crops under combined use of organic and inorganic fertilizers on Oxisols and Inceptisols in eastern Rwanda and to determine the best fertility management options. The DSSAT crop models were used to quantify the alternative production activities. The simulation of crop yield showed that predicted crop yield was distinctly higher than the actual yield for the current small-scale farming practices common in the region. The predicted yields for beans (Phaseolus vulgaris), groundnut (Arachis hypogaea), and cassava (Manihot esculenta) were approximately the same for all treatments, whereas the combined application of Tithonia diversifolia and Diammonium phosphate appeared to predict higher yields for maize (Zea mays) and sorghum (Sorghum bicolor). Yield prediction for all crops was higher on the Inceptisols than on the Oxisols because of the better chemical and physical conditions of Inceptisols. This is in line with reality. © 2012 Copyright Taylor and Francis Group, LLC.

Mawussi G.,University of Lomé | Scorza Junior R.P.,Embrapa Western Agriculture | Dossa E.L.,International Center for Soil Fertility and Agricultural Development | Alate K.-K.A.,University of Lomé
Environmental Monitoring and Assessment | Year: 2014

Some common organochlorine, organophosphorus and pyrethroid insecticides were analysed in agricultural soil samples (n = 35) and surface water and groundwater samples (n = 25) collected from coastal areas of vegetable production in Togo. Analytical methods included solvent extraction of the insecticide residues and their subsequent quantification using GC-ECD. δ-HCH, heptachlor epoxide, 4,4-DDE, endosulphan (α, β and sulphate), lambda-cyalothrin and chlorpyrifos were found in the soil samples with concentrations that varied from non-detectable (ND) to 26.93 μg kg−1 dry weight. For water samples, heptachlor epoxide, 2,4-DDD, 4,4-DDD, 4,4-DDE and endosulphan (α, β, and sulphate) were found at contamination levels that varied from ND to 0.116 μg L−1. The concentration of insecticide residues detected in the water samples was below the limits set by the World Health Organization (WHO) and also by the European Union (EU), with the exception of the concentration of endosulphan sulphate at the Aného site, which was 0.116 μg L−1. © 2014, Springer International Publishing Switzerland.

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