Growth and Yield Responses of Cowpea ( Vigna unguiculata (L.) Walp) Genotypes to Nitrogen Fertilizer (NPK) Application in the Southern Guinea Savanna Zone of Nigeria

摘要

The effects of compound fertilizer (NPK) application on growth and yields of cowpea genotypes were investigated in a field study at the Teaching and Research Farm of the University of Ilorin, Ilorin in the Southern guinea savanna zone of Nigeria. The study was designed as a series of factorial experiments in split-plot arrangements with four replications and were carried out in the late cropping seasons (August to December) of 2002 to 2004. Ten cowpea genotypes were evaluated at fertilizer levels ranging from 0 to 300 kg fertilizer (NPK) ha^-1 (equivalent to 0-0-0 to 60-30-30 kg N-P-K ha^-1). Results show that fertilizer application resulted in significant improvement in plant height, number of leaves per plant and reduced days to flowering, but no significant effect on total number of flowers produced. Application of fertilizer resulted in significant decreases in nodule production. Yield component s and grain yield were significantly enhanced by the application of fertilizer at 150 kg ha^-1 (i.e., 30 kg N, 15 P₂O₅ and 15 K₂O ha^-1), but significant fertilizerxgenotype effect indicated differential genotype responses to fertilizer application which may have significant practical implications for field production. It was therefore concluded that the application of fertilizer to cowpea is beneficial although in small quantity and genotype dependent.