NUTRIENT REMOVAL BY WEEDS IN SOYBEAN (GLYCINE-MAX) UNDER INTEGRATED WEED MANAGEMENT

An experiment conducted during the rainy season of 1993 and 1994 showe d that weeds in soybean [Glycine mar (L.) Merr.] depleted the soil fer tility by removing 53.24 kg N/ha and 9.30 kg P/ha under unweeded check . Pre-plant application of trifluralin @ 1.0 kg/ha followed by fluazif op-p-butyl @ 0.75 kg/ha at 20 days after significantly reduced the nit rogen and phosphorus removal by barnyard grass [Echinochloa colonum (L .) Link], while trifluralin @ 1.0 kg as pre-plant followed by chlorimu ron 6.0 g/ha at 20 days proved very effective in decreasing the N and P removal by quail grass (Celosia argentea L.) and horse purslane (Tri anthema portulacastrum L.). Pre-plant trifluralin or pre-emergence pen dimethalin each @ 1.0 kg/ha, followed by 1 hoeing at 35 days resulted in significant reduction in nutrient removal by weeds and significant increase in nutrient uptake by soybean and consequently higher grain y ield.