Effect of pre emergence and post emergence herbicides on weed control in irrigated blackgram

Field experiments were conducted to find out the effect of pre and post emergence herbicides and hand weeding practices on weed control and yield of irrigated blackgram at TNAU, Coimbatore during rabi season 2011-12 under irrigated condition using recently released blackgram variety Co.6. In this experiment, chemical weed management practice of pre emergence application of Pendimethalin 30 EC + Imazethapyr 2 EC as Vallore 32 @ 0.75 kg and 1.0 kg a.i. ha-1 at 3 DAS, post emergence application of quizalofop ethyl and imazethapyr each @ 50 g a.i. ha-1 and their combination at 15 DAS and the sequential application of pendimethalin @ 1.0 kg ha-1 at 3 DAS followed by either quizalofop ethyl or imazethapyr each @ 50 g a.i. ha-1 and their combinations were tested against integrated weed management practice of pre emergence application pendimethalin @ 1.0 kg a.i. ha-1, Vallore 32 @ 0.75 kg and 1.0 kg ha-1 with a follow up hand weeding at 30 DAS and hand weeding twice keeping weedy check and weed free check as controls in a randomized block design replicated thrice. Integrated weed management practice of pre emergence application of Pendimethalin 30 EC + Imazethapyr 2EC as Vallore 32 @ 1.0 kg a.i. ha-1 with follow up hand weeding recorded 70 and 68 % lowest weed population at 40 and 60 DAS with comparable effect from hand weeding twice, WCE was higher 94.10 and 91.66 per cent respectively, Weed index marginal yield reduction of 2.59 per cent, weed dry weight recorded lesser 19.61 kg ha-1 and weed density also significantly reduce. Application of Pendimethalin 30 EC + Imazethapyr 2EC as Vallore 32 @ 1.0 kg a.i. ha-1 with follow up hand weeding registeredsignificantly taller plants, higher dry matter production, more number of pods per plant, seeds per pod and higher grain yield (1052 kg ha-1), net returns (Rs. 32963 ha-1) and benefit cost ratio (2.52). Thus, application of pre emergence application of Pendimethalin 30 EC + Imazethapyr 2EC as Vallore 32 @ 1.0 kg a.i. ha-1 with one follow up hand weeding recommended as weed management practices on the basis of better weed control, crop yield and economic indices.