Effect of stage and intensity of defoliation on the performance of vegetable cowpea (Vigna unguiculata (L.) Walp)

Field experiments were conducted in 2006 and 2007 on the experimental farm of the Institute for Agricultural Research, Ahmadu Bello University, Samaru, Zaria to determine the effect of stage and intensity of defoliation on the performance of vegetable cowpea. The treatments were laid out in a randomized complete block design replicated three times. The treatment consisted of factorial combination of three growth stages (vegetative, flowering and podding) and five defoliation intensity (0, 25, 50, 75 and 100). Artificial defoliation was carried out at each of the stages at different intensities. Defoliation for vegetative, flowering and podding were carried out at 5, 7 and 9 weeks after sowing respectively. Cowpea defoliated at the early stages just prior to podding significantly (p 0.05) reduced both growth and developmental characters. Also, the yield and yield components were significantly reduced by early defoliation. The intensity of defoliation significantly affected the growth and development of cowpea and the yield loss increased as the percentage of defoliation was higher. The interaction between stage and intensity of defoliation was significant for pod yield and shows that defoliating up to 50% at vegetative and flowering stages was detrimental to yield of vegetable cowpea.