Abstract
A field experiment was conducted during November-May 1984 and 1985 to evaluate the effect of row spacing, seed rate, sowing method and weed control measures on the uptake of nutrients by different categories of weeds and the availability of nutrients to the crop. Closer row spacing, higher seed rate and cross-sowing significantly decreased the nutrient removal by grass and broad-leaf weeds, as well as by a sedge, compared with wider row spacing, normal seed rate and one-direction sowing, and resulted in higher nutrient uptake by the crop. Uncontrolled weeds over a period of 90 days depleted on average 69, 15 and 52 kg N, P and K ha-1, resulting in 48, 41, and 54% crop loss in N, P and Kin weedy plots, compared with the crop in weed-free conditions. The uptake of nutrients was greatest in grass weeds and least in the sedge; broad-leaved weeds removed nutrients at a moderate rate. lsoproturon at 0.5 and 1.0 kg a.i. ha -1 reduced the nutrient removal by the different weed categories appreciably, leading to increase in nutrient uptake by the crop.
