Abstract

A two-year field study was conducted in 2003 and 2004 at the Teaching and Research Farm, Bolorunduro (8^o 29’ N, 4^o 35’E ) of the University of Ilorin, Nigeria, to evaluate the growth and grain yield responses of soybean genotypes to P fertilizer application. The trial was designed as 12 x 2 factorial experiments in randomized complete block and laid out in split-plots arrangements with four replications. The main plots were twelve soybean genotypes, while two P fertilizer levels constituted the sub-plots. Plant height, leaf area and number of branches per plant, crop growth rate, relative growth rate, net assimilation rate and leaf area ratio were measured at full flowering, while number of pods per plant and grain yield were obtained at harvest.  Plant height, leaf area, number of branches, crop growth rate, relative growth rate varied significantly (p < 0.001) among genotypes and increased significantly (p < 0.01) with P fertilizer application in both years of study. Similarly, number of pods per plant and grain yield differed significantly among genotypes and increased with P application in the two years of study, but the differences were significant only in 2003. The results also showed appreciable variations in grain yields of the genotypes at 0 kg P ha^-1, suggesting variations in P use efficiency of the genotypes at low level of P. In conclusion, results of this study showed significant positive responses to P application.

Key words: Growth, grain yield, phosphorus fertilizer, Glycine max.