Influence of Integrated Weed Management Practices on Weed Competition for Nutrients in Puddle-sown Rice

A field experiment was conducted during kharif 1994 and 1995 to study the effect of herbicides in conjunction with halod (an interculture operation in standing rice crop) on direct seeded puddle rice and associated weeds. In weedy check, weeds depleted 107.0, 15.5 and 112.8 kg/ha of nitrogen, phosphorus and potassium, respectively, which was 60.8, 6.85 and 46.6 kg more than the total uptake of these nutrients by rice crop. Preemergence application of pretilachlor 0.80 kg/ha and butachlor 1.50 kg/ha at seven days after sowing (DAS) remaining statistically at par with post-halod hand weeding was significantly better than all post-halod herbicide treatments (pretilachlor 0.80 kg/ha, butachlor 1.50 kg/ha and 2, 4–0 (ethyl ester) 0.50 kg/ha alone and in combination with pretilachlor 0.40 kg/ha and butachlor 0.75 kg/ha), with regard to uptake of N, P and K by weeds and rice. Amongst post-halod herbicide treatments, tank mixed combinations of butachlor and pretilachlor with 2, 4–0 were significantly uperior in decreasing nutrients uptake by weeds and were as effective as farmers, practice of halod followed by hand weeding in increasing the uptake of all the nutrients by rice crop.