Production of cowpea [Vigna unguiculata (L.) Walp.] leaves as vegetables is the primary goal of many producers. Little is known about how leaf harvesting practices affect N2 fixation and leaf and grain yields. Better information would help optimize overall production of leaves and grain. The objective of this study was to establish an optimal time from crop emergence when harvesting of leaves can be initiated and a frequency of leaf harvesting that would give good vegetable leaf yield without compromising grain yield and N2 fixation. Two cowpea cultivars, Kathoka and Ex-Luanda were used. Leaf harvesting initiation (LHI) was at 2, 4, or 5 wk after emergence (WAE). Leaf harvesting frequency was at 7- or 14-d intervals. Kathoka produced higher total leaf weight than Ex-Luanda, while Ex-Luanda produced more grain yield and nodule weight than Kathoka. Initiating leaf harvesting at 2 WAE gave higher leaf yield but lower grain yield and nodule weight. Initiating leaf harvesting at 5 WAE gave very low leaf yields but high grain yield, as might be expected. Optimum LHI was at 4 WAE and provided adequate leaf yield with acceptable grain yield and nodule weight. Weekly leaf harvesting gave higher leaf yield but lower grain yield and nodule weight than biweekly leaf harvesting. Control plants had the highest grain yield and nodule weight. These data show that producers could potentially optimize production of leaf and grain according to their goals.
Saidia, M.; Ngouajiob, M.; Itulyaa, F.M.; Ehlers, J. Leaf harvesting initiation time and frequency affect biomass partitioning and yield of cowpea. Crop Science (2007) 47 (3) 1159-1166. [DOI: 10.2135/cropsci2006.06.0420]