Enhancing wheat water productivity through optimized water supply–demand matching under no-tillage and reduced nitrogen fertilization in arid irrigated regions

Wheat production in arid irrigated regions relies heavily on intensive tillage, high nitrogen (N) input, and irrigation, which may lead to high nonproductive water loss and limited improvement in water productivity (WP). However, it remains unclear whether no-tillage combined with reduced N input can improve water productivity by regulating soil water supply, evapotranspiration partitioning, and dry matter formation across growth stages. A 2‑year field experiment was conducted in Wuwei, Gansu Province, China, involving four treatments: conventional tillage with high N (CT-N225; 225 kg N ha 1 ), no‑tillage with high N (NT-N225; 225 kg N ha 1 ), no‑tillage with 20% N reduction (NT-N180; 180 kg N ha 1 ), and no‑tillage with 40% N reduction (NT-N135; 135 kg N ha 1 ). Compared with CT-N225, NT-N180 increased soil water content and storage, reduced early‑season (seeding and tillering) evaporation, and improved mid‑season (jointing and booting) transpiration anddry matter (11.5–17.7%). Consequently, grain yield increased by 7.8% and WP by 6.2–8.8% ( P < 0.05). These improvements were associated with suppressed early-stage evaporation, enhanced mid-season transpiration, a shift in the peak of water-carbon synergy to the jointing-booting stage, and improved the temporal coupling between water supply and demand (synchrony index > 0.74). Furthermore, NT‑N180 and NT‑N225 demonstrated more stable synchrony indices over the entire growing season. These findings indicate that no‑tillage with moderate nitrogen reduction can improve WP by optimizing ET partitioning and water‑use timing, providing a water‑saving and nitrogen‑efficient strategy for wheat production in arid irrigated regions.