Maximizing water and nitrogen productivity in aerobic rice through optimized drip irrigation and nitrogen fertilization

Abstract

Global water scarcity and nitrogen (N) fertilizer pollution threaten the sustainability of rice production, necessitating a shift towards water and N-efficient cultivation methods. This two-year study aimed to optimize water and N productivity in aerobic rice by assessing four drip irrigation regimes (I 1 :1.25, I 2 :1.50, I 3 :1.75, and I 4 :2.00 times pan evaporation (Epan)) and four N fertilization rates (N 1 :90, N 2 :120, N 3 :150, and N 4 :180 kg N ha − 1 ) on a sandy clay loam soil in Tirupati, India. A split-plot design was employed to evaluate the effects on grain yield, irrigation water productivity (IWP), total water productivity (TWP), and partial factor productivity of N (PFP N ). Results showed that higher irrigation regimes (I 4 and I 3 ) combined with 180 kg N ha − 1 significantly maximized grain yield, exhibiting increases of 48.8% and 44.0%, respectively, compared with the I 1 N 1 treatment. However, water productivity declined with increasing irrigation levels, and the highest IWP (5.93 kg ha-mm − 1 ) and TWP (4.75 kg ha-mm − 1 ) were recorded under I 2 N 4 , indicating a trade-off between maximizing yield and water productivity. Increased N application significantly enhanced grain yield from 3294 kg ha − 1 (N 1 ) to 4242 kg ha − 1 (N 4 ), and improved N uptake, whereas PFP N declined from 36.60 kg kg − 1 (N 1 ) to 23.57 kg kg − 1 (N 4 ). Notably, the I 3 N 4 treatment (1.75 Epan with 180 kg N ha − 1 ) provided a balanced strategy by achieving high grain yield while reducing total water use by 19.8% compared with I 4 N 4 . Therefore, I 3 N 4 may be considered a practical irrigation-nitrogen combination for balancing grain productivity and resource-use efficiency under drip-irrigated aerobic rice cultivation.