Protein Productivity and Economic Feasibility of Dual-purpose Cowpea

Abstract

The effect of leaf harvest on the total protein yield and economic viability of cowpea [Vigna unguiculata (L.) Walp.] was evaluated under tropical field conditions. Productivity was measured as edible dry weight and protein yield in kg·ha-1 dry-weight basis (dwb). Calculation of the economic feasibility of the dual-purpose cowpea (leaf and seed harvest) vs. seed-only harvest was based on the net income. Each cultivar was grown on four row plots, with rows 60 cm apart × 5 m long. Only the two central rows were harvested. Two treatments (leaf harvest and no leaf harvest) constituted the main plots, with the varieties as subplots. Leaf harvest was restricted to the most recent, fully expanded third and fourth trifoliate leaves from the apical bud, and extended from 28 days after planting until 50% flowering. Significant (P < 0.05) cultivar differences were observed for leaf yield, seed yield, maturity, and protein yield. Dual-purpose use extended mean time to maturity by 6 days. The mean seed yield across 12 cultivars was 1260 and 976 kg·ha-1 for seed-only vs. dual-purpose, respectively. Leaf harvest reduced mean seed protein yield for six cultivars by 23%. The mean gross incomes from the dual-purpose and seed-only harvests were $1092 and $912, respectively, but the protein productivity and net income for the dual-purpose system were 1.4 and 1.5 times as great, respectively, as for the seed-only harvest system. Thus, the increased protein yield associated with the dual-purpose harvest was financially warranted.