Management of weeds in aerobic rice under different agro ecologies of North East India

Abstract

The field experiment was carried out to study the importance of weed management and efficiency of different weed management practices both chemical and nonchemical method in aerobic rice. The field experiment was carried out in a randomized block design with twelve treatments and three replication. In the experiment chemical and nonchemical methods are used either alone or in combination. Rice variety NDR-97 was taken for the purpose. The upland rice was fertilized as per recommended package of practices in Tripura. Weed counts at different stages (15, 30, 60 and at harvest stage) was taken by placing quadrat at random from three sites in each plot and calculating the average. Weed sample from each of the quadrat was taken, grouped into grasses, broad leaved weed and sedges, dried and weighed. Weed dry matter was expressed category wise in g m-2. Data on growth parameters, yield attributes and yield of rice were taken. Economics of different weed management practices was also calculated. The data generated from the experiment were subject to analysis of variance (ANOVA) as applied to randomized block design. Among the various weed management practices, hand weeding at 15, 30 and 45 DAS has recorded the lowest weed dry weight, highest weed control efficiency, highest grain and straw yield followed by pendimethalin @ 1.0 kg ha-1 + one hand weeding at 30 DAS and pendimethalin @ 1.0 kg ha-1 at 2 DAS + bispyribac sodium @ 25 g ha-1 at 20 DAS. Highest dry weight of weed, lowest weed control efficiency, lowest grain and straw yield was obtained with weedy check where weed management practices were not adopted. Though the rice yield and gross return were the highest under hand weeding at 15, 30 and 45 DAS, net income and return per rupee invested showed that it was less remunerative than pendimethalin @ 1.0 kg ha-1 at 2 DAS + bispyribac sodium @ 25 g ha-1 at 20 DAS and pendimethalin @ 1.0 kg ha-1 + one manual weeding at 30 DAS. For successful crop production adoption of weed management practices is very much necessary. Acceptance of any weed management practices depends on the economic viability of the practices. The net return and B C ratio obtained with hand weeding at 15, 30 and 45 DAS implied that it was uneconomic and unnecessary to give three hand weeding during the entire crop growth.