Irrigation scheduling and nitrogen strategies to enhance wheat yield and water productivity under subtropical conditions

Efficient management of irrigation and nitrogen is essential for sustaining wheat production under increasing water scarcity in subtropical regions. This study tested the hypothesis that moderate deficit irrigation combined with the recommended nitrogen rate can optimize grain yield while improving water-use efficiency, and that wheat varieties differ in their response to water stress. A two-year field experiment of the cropping years 2018-19 and 2019-20 was conducted at Roorkee, North India, using a split–split plot design with three irrigation frequencies (three, four, and five irrigations), two nitrogen levels (75 and 90 kg N/acres), and three wheat varieties. Grain yield, consumptive use efficiency (Ecu%), water productivity (WP), irrigation water productivity (PIW), water savings, yield response factor (Ky), and evapotranspiration (ET) estimated by different methods were evaluated. Results indicated that irrigation frequency had a stronger influence on yield and water-use indices than nitrogen level. Four irrigations consistently maximized grain yield, whereas three irrigations significantly enhanced WP, PIW, and water savings with only a marginal yield reduction. Increasing nitrogen beyond the recommended rate did not significantly improve yield but increased water consumption, leading to lower efficiency. Among cultivars, HD2967 produced the highest grain yield and exhibited greater drought tolerance (Ky = 0.51) compared with UP2572 and UP2584. The FAO Penman–Monteith method showed the closest agreement with measured ETa, confirming its suitability for irrigation planning under subtropical conditions. Overall, the study demonstrates that four irrigations combined with 75 kg N /acres and the HD2967 cultivar provide the best balance between high yield and efficient water use, offering a practical and sustainable irrigation–nitrogen strategy for wheat production in subtropical North India.