Contribution from National Research Centre for Weed Science, Adhartal Jabalpur-482004 (M.P.), India.
Weeds competed severely with the crop for nitrogen supply and the competition commenced quite early in the season. Maximum removal of nitrogen from the soil were observed 60 days after sowing (d.a.s.) the crop. Weed removal once on 30th or 45th day, twice (15 & 30 or 15 & 45 or 30 & 45 d.a.s.) or thrice (15 & 30 & 45 d a.s.) reduced the campetition and total nitrogen uptake by weeds and that by major weed species viz; E. colonum, Trianthema portulocastrum and Digera arvensis was significantly below that in the unweed check at the successive stages of crop growth. N uptake of weeds was found negatively correlated with N uptake of rice (r=0.789).
