Effects of Phosphorus and Rhizobium Inoculation on Yield Components and Grain Yield of Some Selected Cowpea Genotypes

The effects of phosphorus (0, 20, 40kg P2O5ha-1) and rhizobium inoculation (inoculated and un-inoculated) on the yield components and grain yield of three cowpea genotypes (IT93K-452-1, IT97K-573-1-1 and IT98K-499-35) were investigated under field conditions at Bayero University, Kano, Teaching and Research Farm (11059 N; 8025 E; 466m above sea level) and Agricultural Research Station Farm, Minjibir (12010’ N,  8039’ E; 402m  above sea level) in 2014 rainy season. Cowpea genotypes were assigned to the main plot, while phosphorus levels were assigned to the sub-plots. The inoculation was assigned to the sub-sub plot. These were laid out in Split-split plot design and replicated three times. Results of the study indicated significant effect of genotype in all the characters measured except shelling percent. Significantly (p˂ 0.05) higher number of pods per plant, pod weight, fodder and grain yield was observed from IT99K-573-1-1 than all other genotypes evaluated. Similarly, the number of pods per plant, pod weight, fodder and grain yield were significantly influenced by application of phosphorus with better results recorded from 40 kg P2O5 treated plants. Inoculation of cowpea with rhizobium MC92 strain, also recorded significant effect on the measured characters and grain yield. Inoculation of cowpea with rhizobium MC92 along with 40kgP2O5 ha-1 could enhance performance of cowpea particularly with an adaptable genotype like IT99K-573-1-1. Keywords: Cowpea, grain yield, inoculation, yield component