Modeling nutrient and water productivity of sorghum in smallholder farming systems in a semi-arid region of Ghana |
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Authors: | Dilys S. MacCarthy Paul L.G. Vlek A. Bationo R. Tabo M. Fosu |
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Affiliation: | 1. ZEF, Zentrum für Entwicklungsforschung, University of Bonn, Walter-flex str. 3, D-53113 Bonn, Germany;2. Tropical Soil Biology and Fertility Institute of CIAT (TSBF-CIAT), P.O. Box 30677-00100, Nairobi, Kenya;3. International Crop Research Institute for the Semi-Arid Tropics (ICRISAT)-West and Central Africa Unit. P.O. Box 12404, Niamey, Niger;4. Savanah Agriculture Research Institute (SARI), P.O. Box 52, Nyankpala, Tamale, Ghana |
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Abstract: | The CERES-sorghum module of the Decision Support System for Agro-Technological Transfer (DSSAT) model was calibrated for sorghum (Sorghum bicolor (L.) Moench) using data from sorghum grown with adequate water and nitrogen and evaluated with data from several N rates trials in Navrongo, Ghana with an overall modified internal efficiency of 0.63. The use of mineral N fertilizer was found to be profitable with economically optimal rates of 40 and 80 kg N ha−1 for more intensively managed homestead fields and less intensively managed bush fields respectively. Agronomic N use efficiency varied from 21 to 37 kg grain kg−1 N for the homestead fields and from 15 to 49 kg grain kg−1 N in the bush fields. Simulated grain yield for homestead fields at 40 kg N ha−1 application was equal to yield for bush fields at 80 kg N ha−1. Water use efficiency generally increased with increased mineral N rate and was greater for the homestead fields compared with the bush fields. Grain yield per unit of cumulative evapo-transpiration (simulated) was consistently higher compared with yield per unit of cumulative precipitation for the season, probably because of runoff and deep percolation. In the simulation experiment, grain yield variability was less with mineral N application and under higher soil fertility (organic matter) condition. Application of mineral N reduced variability in yield from a CV of 37 to 11% in the bush farm and from 17 to 7% in the homestead fields. The use of mineral fertilizer and encouraging practices that retain organic matter to the soil provide a more sustainable system for ensuring crop production and hence food security. |
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Keywords: | BD, bulk density SAT, volumetric water content at saturation LL, lower limit DUL, drained upper limit CERES, Crop Evaluation through Resource and Environment DSSAT, Decision Support System for Agro-Technological Transfer E1, modified coefficient of efficiency CGIAR, Consultative Group on International Agricultural Research FAO, Food and Agriculture Organisation AEN, agronomic efficiency of mineral N use SYI, sustainable yield index |
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