Field experiments were conducted at Wetland Farm of Tamil Nadu Agricultural University, Coimbatore during late samba, 2005-06 and kuruvai, 2006 to find out the optimum nitrogen level and effective weed management practice for aerobic rice cultivation. Three N levels (100, 125 and 150 kg N ha-1) in main plots and five different weed management practices (Hand weeding twice, mechanical weeding twice, pre-emergence application of pendimethalin at 0.75 kg ha-1 + one hand weeding on 45 DAS, pretilachlor plus safener at 0.4 kg ha-1 + one hand weeding on 45 DAS and unweeded control) in sub plots were studied. Results revealed that application of 150 kg N ha-1 registered significantly higher number of tillers, panicles (349 and 235 m-2), filled grains per panicle (104.7 and 76.3) 1000-grain weight (24.5 and 23.9) and grain yield (3424 and 2212 kg ha-1) than 100 kg N ha-1 respectively during both the years. However, it was on par with 125 kg N ha-1 (3213 and 2036 kg ha-1 respectively). In weed management practices, pre-emergence application of pendimethalin at 0.75 kg ha-1 followed by one hand weeding on 45 DAS registered significantly lesser weed density, dry weight and higher weed control efficiency (WCE), followed by pretilachlor plus safener at 0.4 kg ha-1 followed by one hand weeding on 45 DAS. Hand weeding twice at 25 and 45 DAS was found to be superior in growth, yield attributes and grain yield of aerobic rice (3976 and 2349 kg ha-1), closely followed by pre-emergence application of pendimethalin at 0.75 kg ha-1 followed by one hand weeding on 45 DAS.
Ramesh et al. (Thu,) studied this question.