Impact of water and nitrogen management strategies on productivity, resource use efficiency, and greenhouse gases emission in aerobic rice

Rice is known for its luxurious water and nutrient consumption, making it a major contributor of greenhouse gases (GHG) emission among the arable crops. To sustain rice production systems, optimization of water and nutrients supply, besides reducing GHG emission is the utmost concern. To address these issues, a study was conducted for two consecutive years at the University of Agricultural Sciences, Bangalore, Karnataka (India). The split-plot experiment comprised of three irrigation levels in the main plot and six nitrogen management practices in the sub plot. The results of the pooled analysis showed an increase in grain yield of aerobic rice with increased application of irrigation and PU (prilled urea), yet promoted higher GHG emission. Among the varied irrigation levels, irrigation at 1.0 IW/CPE (Irrigation water to Cumulative pan evaporation ratio) increased the WUE (Water use efficiency) with 10% less water, accounting for 12.08% lesser GWP (Global warming potential) compared to irrigation at 1.2 IW/CPE. Among the nitrogen management strategies, replacing 25% RDN (Recommended nitrogen) supplied through PU by two foliar sprays of NU (Nano urea) enhanced nitrogen use efficiency and helped in significant reduction of GHG emission (by ∼6.5%), accounting for the highest eco-efficiency of rice production (Rs. 12.26 kg -1 CO 2 eq.) without significant yield reduction. Hence, irrigation at 1.0 IW/CPE and application of 75% RDN through PU + 2 NU sprays at 30 and 60 DAS is recommended for attaining higher grain yield of aerobic rice besides reduced GHG emission.