Water Management Practices and Nitrogen Sources Effects on N-mineralization and Use Efficiency in Rabi Paddy (Oryza sativa L.) in Southern Telangana

A field study was conducted on clay loam soil at college farm, College of Agriculture, Rajendranagar, Hyderabad, Telangana, India During Rabi 2015-16 and Rabi 2016-17, to investigate the effect of water management strategies and nitrogen sources on rice N-mineralization patterns. The experiment was laid out in a split plot design under two types of water management practices i.e., Continuous flooding (CF) and alternate wetting and drying (AWD) as main treatments with five treatments viz., T1- N0:P2O5 @ 60 kg ha-1: K2O @ 60 kg ha-1 (Control); T2- Nitrogen @ 120 kg ha-1 (Prilled Urea): P2O5 @ 60 kg ha-1: K2O @ 60 kg ha-1 T3- Soil test based Nitrogen fertiliser application (STCR); T4- Nitrogen @ 60 kg ha-1 + 60 kg ha-1 through green manure and T5- Nitrification inhibitor Coated Urea as sub plot treatments. The MTU-1010 variety was grown with the recommended management practices. Continuous flooding plots were kept at a 5cm water level at all times, while alternate wetting and drying plots were irrigated when a hairline fissure emerged on the soil surface.

Significantly NH4+-N content increases with time and peaked at 15 DAT under continuous flooding as well as alternate wetting and drying (27.12 mg kg-1 and 28.28 mg kg-1). Green manure treatment resulted in faster NH4+ -N release and accumulation, in the order of Green manure > PU > STCR > coated urea > control treatments. In comparison to STCR and green manure, NO3--N release was low in coated urea, followed by prilled urea. Alternate wetting and drying resulted in 29 per cent greater AE than continuously flooded rice. The treatment which receives nitrogen through STCR (21.30 kg grain yield per kg N applied and 23.94 kg grain yield per kg N applied) followed by nitrification inhibitor coated urea treatment had the highest AE.