Response of Cowpea (Vigna unguiculata (L) Walp) to Nitrogen Fertilizers and Leaf Plucking Frequencies

Abstract

Cowpea (Vigna unguiculata) seeds and leaves are an important item in the diet of most farmers in the tropics. The tender and succulent leaves are generally plucked and used as green vegetables until about flowering, when leaf plucking stops. Defoliation may adversely affect seed yield due to reduction in photosynthetic area. One possible means of reducing the adverse effects of defoliation on seed yield is, to apply additional nitrogen fertilizer to stimulate vegetable growth, hence this experiment. The effects of three nitrogen levels (0,50 and 100 kg/ha) and four leaf plucking treatments (no plucking, plucking once a week, once in two weeks and once in three weeks) on leaf and seed yield of cowpeas were investigated at the University of Swaziland, Faculty of Agriculture, Luyengo during the 1997/98 growing season. The design of the trial was randomized complete block with twelve treatment combinations and each was replicated three times. Data collected included canopy height and width, area of plucked leaves, fresh and dry weight of plucked leaves, 100-seed mass, seed yield and monetary value of seeds and leaves. Data showed that additional nitrogen increased seed yield significantly (P<0.01). Plucking cowpea leaves weekly had more adverse effect on seed yield than the other leaf plucking treatments. Leaf area and 100-seed weight were the yield components mostly affected by leaf plucking. Although leaf plucking caused reduction in seed yield, the combined monetary value of seeds and plucked fresh leaves was generally higher than those from unplucked plants. The implications of these findings for farmers who utilize both leaves and seeds for relish are discussed.

UNISWA Research Journal of Agriculture, Science and Technology Vol 3 (1) 1999: pp 50-55