Efficacy of Pre and Post-emergence Herbicides on Weed Dynamics, Growth, Yield and Economics of Summer Cowpea [Vigna unguiculata (L.) Walp.]

Background: A field study was conducted during the summer season, 2023 to evaluate the impact of pre-emergence and post-emergence herbicides on the growth, yield and weed dynamics of cowpea (Vigna unguiculata L.). Poor weed management during the crop’s critical growth phase often results in substantial yield reductions ranging from 25% to 76%. Herbicide application offers a cost-effective alternative to manual weeding, particularly as labor costs continue to rise. Methods: The study was designed in completely randomized block design comprising of ten treatment groups, incorporating combinations of two PE and POE herbicide applicationin addition to the treatments, one weed-free check completely weeding (manual weeding) and one weedy check treatment (unweeded control) were included for comparison. Result: The experiment results indicated that the combination of pendimethalin @ 750 g ha-1 (pre-emergence) and quizalofop-p-ethyl @ 80 g ha-1 (post-emergence) applied 20 days after sowing (DAS) recorded the lowest weed density, biomass and weed index. This treatment also registered the higher crop growth, yield parameters and weed control efficiency and was statistically on par with the weed-free control and the sequential application of Pendimethalin at 750 g/ha + Fenoxaprop-P-ethyl at 100 g/ha applied at 20 days after sowing (DAS). The highest net income was recorded with the sequential application of (PE) Pendimethalin (750 g ha-1) + (PoE) Fenoxaprop-p-ethyl (100 g ha-1) at 20 DAS, with a marginal difference observed in comparison to (PE) Pendimethalin (750 g ha-1) + (PoE) Quizalofop-p-ethyl (80 g ha-1) at 20 DAS. Based on availability, either of these two herbicide combinations can be recommended to the farmers for efficient weed control in cowpea. These results highlight the effectiveness of certain herbicide combinations in enhancing weed management and boosting cowpea yield.