Georgis, Kidane2006-12-292006-12-2919971997http://hdl.handle.net/2440/22425Bibliography: leaves 155-169.xiv, 169 leaves : ill. ; 30 cm.Studies the effect of nitrogen fertilizer on dry matter production under differing watering regimes. Investigates the accuracy of different crop and soil organic matter models for predicting crop yield, nitrogen uptake and changes in soil organic carbon and nitrogen. Compares the models with data from long-term field experiments on wheat in Australia and sorghum in Ethiopia. Finds that a higher crop yield and better nitrogen and water utilisation can be achieved if addition of nitrogen fertilizer is balanced with soil water.295953 bytesapplication/pdfenNitrogen fertilizers Arid regions.Crop yield Arid regions Computer simulation.Soils Arid regions Composition Computer simulation.Humus Arid regions Computer simulation.Thesis