Seed priming with melatonin improves yield and water productivity of winter wheat under limited irrigation at field scale

As a pivotal wheat production base, the North China Plain faces chronic agricultural challenges due to severe groundwater depletion and insufficient precipitation. Melatonin (MT), an effective drought-regulating agent, remains underutilized in water-saving wheat production. A split-plot field experiment (2022–2024) on winter wheat compared W1 (jointing-stage irrigation) vs. W0 (no spring irrigation) as main plots, with subplots of NP (no priming), HP (hydropriming), and MP (melatonin priming). Results showed that wheat yield and 1000-grain weight under MP were significantly increased by 11.8% and 5.1% respectively compared with NP, and spike number was significantly increased by 6.5% and 4.1% respectively compared with NP and HP. Correspondingly, spike number and yield under W1 were higher by 13.7% and 23.0% than that under W0, whereas 1000-grain weight was significantly reduced by 4.9%. Similarly, compared with NP and HP treatments, tillering number under MP increased by 5.9% and 4.0%, and dry matter accumulation increased by 13.9% and 6.6%, respectively. Longer roots under MP, which were 15.4% and 10.6% higher than that under NP and HP respectively, enhanced later soil water absorption in the 60–180 cm layer. Under water-limited conditions, water productivity (WP) of MP was significantly higher by 8.4% than NP. MT-primed winter wheat enhanced seedling quality, which provided the foundation for an increase in spike number and 1000-grain weight, and ultimately achieved a synergistic increase in yield and WP. These findings provide a strategy for sustainable development of water-saving agriculture. • Seed priming with MT under one spring irrigation increased innovatively wheat yield and WP in the North China Plain. • MT improved root growth, thus enhancing later soil water absorption in 60–180 cm and promoting dry matter accumulation. • MT could improve seedling quality and ensure sustaining wheat production under limited irrigation.