Monday, November 13, 2006 - 8:15 AM
52-3
Response of Soybean Genotypes to Phosphorus Fertilization in the Tropical Savannas of Northeast Nigeria.
Despite the tremendous increase in production of soybean in the Nigeria savannas, its production is constrained by low levels of soil phosphorus. Biological N2 fixation by legumes requires large amount of P. This study evaluated four soybean varieties for their response to 3 rates of P in northeast Nigeria. Experimental design was a split-plot arrangement of treatments with three replications. The main plots were assigned the P treatments (0, 20, and 40 kg P ha-1) and subplots were assigned the three soybean cultivars. Each plot received a basal application of 30 kg K ha-1 as murate of potash. Average grain yield of soybean was generally higher in Sudan savanna (SS) than in the Northern Guinea savanna (NGS). Application of P at 20 kg P ha-1 significantly increased soybean grain yield in both locations. Grain yield increases at 40 kg P/ha did not significantly differ from those of 20 kg P/ha except in the SS where grain yield of late maturing cultivar, TGX-1448-2E significantly increased by 29%. In the SS, TGX-1448-2E recorded significantly higher grain yield than the two early maturing cultivars (TGX 1485-ID and TGX-1830-20E) at 40 kg P/ha. In the NGS, the two late maturing cultivars had significantly higher grain yield than the early maturing cultivars at both 20 and 40 kg P ha-1. Soybean grain yield did not differ significantly among cultivars when no P was applied indicating the limiting effect of low soil P on growth and yield of soybean. The non-response of most soybean cultivars to P rates above 20 kg P ha-1 in all locations may be due to a limitation of other nutrients. There may be a need to determine the interactive effects of P and other nutrients on soybean in these zones.
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