Response of rice (Oryza sativa) varieties to nitrogen under aerobic and flooded conditions

A field experiment was conducted on a sandy clay loam soil of Central Telangana Zone of Andhra Pradesh during rainy seasons of 2008 and 2009 to compare the performance of popular rice (Oryza sativa L.) varieties, viz. ‘MTU 1001’, ‘WGL 32100’, ‘WGL 14 ‘and ‘WGL 3825’ (check) under aerobic and flooded methods of water management and their response to levels of nitrogen viz. 120. 180 and 240 kg/ha. Cultivation of rice with aerobic method (3.49 t/ha) resulted in 29% yield reduction compared with flooded method (4.93 t/ha). Among the yield attributes, filled spikelets/panicle were significantly affected under aerobic method, while panicles/m², test weight and harvest index were not influenced by the method of water management. ‘WGL 32100’ gave highest grain yield under aerobic (3.94 t/ha) with the least yield reduction (17%) compared to flooded method, while yield gap was high (40%) in ‘MTU 1001’. The water-use efficiency was highest with ‘WGL 32100’ and aerobic method (3.4 kg/hamm), while flooded method showed more nitrogen-use efficiency (33.5 kg grain/kg nitrogen), and nitrogen uptake (76 kg/ha). Higher net returns ( 26,300/ha) and benefit: cost ratio (1.11) were realized with flood irrigated method. Application of 240 kg N/ha resulted in better yield attributes, increased yield (4.50 t/ha), N uptake (72 kg/ha), water-use efficiency (3.0 kg/ha-mm), net returns (23,062/ha) and benefit: cost ratio (1.21), whereas, the nitrogenuse efficiency was superior with 120 kg N/ha (32.5 kg grain/kg nitrogen) both under aerobic and flood irrigated conditions.