Effect of weed management practices on productivity, nutrient depletion by weeds and uptake by transplanted rice (Oryza sativa)

A field experiment was conducted in a randomized block design during the rainy (kharif) season of 2012 at Pantnagar, Uttarakhand, to evaluate the effect of different weed-control treatments on productivity, nutrient depletion by weeds as well as uptake by rice (Oryza sativa L.). Weed-management practices significantly influenced yield, nutrient uptake by rice and depletion by weeds. Pre-emergence application of pretilachlor 750 g/ha + no irrigation up to 1 week followed by (fb) early post-emergence application of bispyribac-Na (20 g/ha) provided broad-spectrum weed-control, resulting in significant reduction in N, P and K removal by the weeds. This treatment also registered the maximum total N, P and K uptake by rice (116.3, 35.6, and 108.7 kg/ha) and significantly higher grain (5.73 t/ha) as well as straw (8.39 t/ha) yields over pre-emergence application of pretilachlor, pretilachlor + no irrigation up to 1 week and cono weeding fb 1 hand-weeding, but remained at par with the other treatments. Application of penoxsulam at both the doses (22.5 and 25 g/ha) was at par with bispyribac-Na 20 g/ha in terms of grain and straw yields.