Assessment of critical period of crop-weed competition in forage cowpea (Vigna unguiculata) and its effect on seed yield and quality

An experiment on crop-weed competition was conducted during the rainy (kharif) season of 2014 at Karnal, Haryana, to determine the critical period of forage cowpea [Vigna unguiculata (L.) Walp.] and its effect on seed yield and quality. Dominated weed species associated with the crop were Trianthema monogyana L., Commelina benghalensis L. and Digera arvensis Forssk. among broad-leaf weeds; and Cyperus rotundus L., Echinochloa colona L., among narrow leaf weeds. Seed yield of cowpea reduced significantly with increase in the duration of crop-weed competition beyond 20 days after sowing (DAS). The seed yield increased significantly with the increase in initial duration of weed-free condition up to 60 days after sowing (DAS) which was at par with 80 DAS and season-long weed-free situation. Critical period of crop-weed competition was found to be between 25–57 days after sowing. Higher net returns and benefit: cost ratio can be realized keeping the crop weed free for first 60 DAS.