Effect of cropweed competition on yield and nutrient uptake by direct-seeded rice (Oryza sativa) in rainfed, lowland situation

Abstract

A field experiment was conducted during wet season of 1995 and 1996 to study the. effect of crop-weed competition on weed growth, yield, and nutrient uptake by direct-seeded rice (Oryza sativa L.). Initial weed-free for 45 days or longer, and weedy up to 15 days after sowing resulted significantly higher rice grain and straw yields, and lower dry weight and nutrient uptake by weeds during both the years. Weed infestation for first 15 days caused no significant loss in grain yield compared to weed-free for 45 or 60 days after sowing. The season- long weedy crop resulted 57% reduction in grain yield compared to season-long weed-free. Initial weed-free for first 30 days caused 25% reduction in grain yield which was higher than loss caused by initially weedy for 30 days (22%). The uptake of nutrients (NPK) by rice crop was significantly higher in weed-free treatment. The season-long weedy depleted 35 N, 15 P,05 and 45,hO kgha by weeds while rice crop under weed-free up to maturity removed 60, 26 and 80 kglha of N, P,05 and \O respectively.