Micro-irrigation improves grain yield and resource use efficiency by co-locating the roots and N-fertilizer distribution of winter wheat in the North China Plain

Highlights: • MI significantly increased yield and water and nitrogen use efficiency compared to TI. • MI significantly promoted matter production post-anthesis, leading to higher yield. • MI optimized water consumption structure thus increased WUE. • MI co-located the roots, water, and NO₃⁻-N distribution in soil thus increased NUE. Water use efficiency (WUE) and nitrogen fertilizer use efficiency (NUE) of winter wheat are urgently needed to further improve in the North China Plain (NCP). In this study, a 3-year field experiment was conducted during the 2014–2017 growing seasons to clarify the effect of traditional flood irrigation (TI), surface drip irrigation (DI), and micro-sprinkling irrigation (MSI) on grain yield, WUE, and NUE of winter wheat. Across the 3 years, grain yield of DI and MSI improved by 9.79% and 14.1%, WUE of DI and MSI increased by 12.3% and 17.7%, and NUE of DI and MSI increased by 9.77% and 14.0%, respectively compared with those of TI. Wheat subjected to the micro-irrigation treatments (DI and MSI) had higher chlorophyll content in flag leaves 10 days post-anthesis; this postponed senescence of the flag leaves, which increased dry matter accumulation post-anthesis, and increased 1000-grain weight and grain yield. The micro-irrigation treatments reduced pre-anthesis water consumption but increased post-anthesis water consumption and ensured the water supply in the top soil layer at the critical stage, thus increasing WUE. Root length density (RLD) of TI in the 0–80-cm soil layer was significantly higher than that of micro-irrigation, whereas micro-irrigation had higher RLD than TI below the 80-cm soil layer, which promoted the absorption and utilization of water and nitrogen in deep soil. The micro-irrigation treatments increased total nitrogen accumulation of the plants, reduced soil nitrate nitrogen (NO₃⁻-N) content at maturity, ensured the nitrogen supply in the top soil layer, thus increasing NUE. Overall, micro-irrigation with water and fertilizer as an integrated pattern significantly improved grain yield, WUE, and NUE of winter wheat in the NCP by co-locating the root, water, and N-fertilizer distribution and reducing NO₃⁻-N accumulation in deep soil. The best treatment was micro-sprinkling irrigation.