Nutrient uptake by sunflower (Helianthus annuus) and associated weeds during rainy season

Abstract

A field experiment on the effect of crop-weed competition on nutrient uptake by rainy-season sunflower (Helianthus annuus L.) and associated weeds was carried out during 1995 and 1996 at New Delhi. Nutrient concentration (N, P and K ) in weeds was greater at younger stages (30 and 45 days after sowing) and decreased towards maturity. Weed-free condition enhanced N and P content in sunflower seeds and K in stalk, while presence of weeds decreased it. Weeds under the unweeded control treatment removed 48.2, 14.4 and 53.5 kg of N, P and Wha, out of which 63.2, 56.7 and 59.1%, respectively, was jointly removed by Trianthema portulacastrum L. and Digera arvensis Forsk. Season-long weed- free crop could remove 125.8 kg N, 51.2 kg P and 125.6 Wha which were 54.3, -- .49.9 and 55.9% more as compared to nutrient removal by crop under weedy check treatment.