Crop Yields after Different Elephant Grass Ley Treatments at Kawanda Research Station, Uganda

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Foster, H. L.
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In an experiment at Kawanda Research Station crop yields declined markedly over two years of a cultivation period. Soil analyses indicated that during this time there was a significant decline in the level of all major soil nutrients, but crop leaf analyses and additional evidence from soil analyses suggested that the loss of soil nitrogen was directly responsible for the poorer yields. Crops grown immediately after three years of unfertilized elephant grass gave much better yields compared with the crops grown after three years of continuous cultivation, irrespective of how the ley was managed. Soil and crop leaf analyses indicated that this was due to a greater availability of spare nitrogen in the soil after the grass rest. Higher yields of maize, but not of cotton, sweet potatoes or beans, were obtained from plots which during the ley phase had received a higher rate of nitrogen fertilizer or had been grazed. A significant decrease in the yield of cotton, sweet potatoes and beans, but not of maize, was recorded on plots where soil potassium had been severely depleted by preceding elephant grass which had received a high rate of nitrogen and phosphate fertilizer, and had been cut. Soil phosphate deficiency was identified by beans in the third arable year, on Plots where previously only elephant grass had received only nitrogen fertilizer and had been grazed.
East African Agricultural and Forestry Journal, 37 (1), pp. 63-72