Effect of nutrient sources on grain yield, methane emission and water productivity of rice (Oryza sativa) under different methods of cultivation

A field experiment was conducted during the rainy seasons of 2012 and 2013 at Zonal Agricultural Research Station, Mandya, to study the sources of nutrient on yield, methane emission, and water productivity of rice (Oryza sativa L.) under different methods of cultivation. Among the different methods of rice cultivation, system of rice intensification (SRI) method recorded higher water productivity (54.3 kg/ha-cm) than aerobic method (46.6 kg/hacm) and conventional method (29.9 kg/ha-cm) and resulted to the higher grain and straw yields of rice (8.55 and 10.07 t/ha) than the other methods of rice cultivation like conventional (7.05 and 8.38 t/ha) and aerobic method (6.48 and 7.83 t/ha). Among the sources of nutrients, application of recommended dose of fertilizer (100% N through neem-coated urea) recorded higher grain and straw yields (8.49 and 9.83 t/ha) over the other sources of nutrients, whereas the aerobic method of rice cultivation recorded lower methane emission (3.95 mg/plant/day) and total methane production (24.2 kg/ha) than SRI method (4.42 mg/plant/day and 28.1 kg/ha) and conventional method (6.25 mg/plant/day and 80.7 kg/ha) 90 days after sowing (DAS). Among the sources of nutrients, application of recommended dose of fertilizer (100% neem coated urea) recorded significantly lesser methane emission (4.35 mg/plant/day) and total methane production (37.9 kg/ha) than the other sources of nutrients but higher methane emission and production resulted by application of 50% N through paddy straw incorporation + 50% N through urea + recommended dose of P and K (5.56 mg/plant/day and 50.5 kg/ha) 90 days after sowing.