Optimizing Onion Yield by Exploring Seasonal Evapotranspiration, Water Productivity and Crop Water Production Functions Under Microsprinkler Irrigation and Nitrogen Fertilization

ABSTRACT Water stress and suboptimal nitrogen fertilization limit sustainable onion production. A two‐season field experiment (2016–2018) evaluated the effects of varying irrigation (0.6, 0.9 and 1.2 ET c as M 1 , M 2 and M 3 ) and nitrogen levels (0%, 75%, 100% and 120% of recommended dose, RDN as N 0 , N 1 , N 2 and N 3 ) on evapotranspiration (ET a ), crop water productivity (CWP), irrigation water productivity (IWP), water‐yield functions and yield response to water stress. Irrigation increased the ET a (163–281 mm) and bulb yield (6.0–9.5 t ha −1 ) while decreasing the CWP (3.01–4.12 kg m −3 ) and IWP (4.13–6.81 kg m −3 ). An optimum balance was found at an average ET a of 220 mm, irrigation of 158 mm, yield of 8.2 t ha −1 and CWP of 3.6 kg m −3 . The overall yield response factor (K y ) was 0.78, indicating that onion is moderately sensitive to water stress, which improved with increasing nitrogen application. Among the treatments, microsprinkler irrigation at 0.9 ET c with 120% RDN (M 2 N 3 ) achieved the highest yield gain (65%), moderate CWP improvement (28%) and maximum net profit (109%) and benefit–cost ratio (107%) over the control (M 1 N 1 ). These results suggest that M 2 N 3 is the optimal strategy for water‐scarce Indo‐Gangetic plains and similar agroclimatic zones.