Micro-sprinkler irrigation based on soil moisture improves wheat grain yield and water-nitrogen utilization by coordinating root and shoot development in the Huaibei Plain of China

Frequent episodic droughts occurring at critical growth stages of winter wheat severely inhibit root and shoot development in the Huaibei Plain of China (HP), which greatly limits the achievement of high-yield and high-efficiency wheat production. A two-year field experiment was conducted to explore the regulatory effects of micro-sprinkler irrigation (MSI) on wheat growth, grain yield (GY) and water-nitrogen use efficiency, with conventional flood irrigation (CI, 60 mm at jointing) set as the control. Two MSI regimes were designed: MSI1 (supplemental irrigation at jointing, booting, and anthesis) and MSI2 (supplemental irrigation at jointing, booting, anthesis, and filling), with each irrigation targeting 75% field capacity in the 0–40 cm soil layer. The novel findings indicated that compared with CI, MSI maintained suitable soil moisture in the 0–20 cm layer but reduced it in the 20–60 cm layer at the jointing-booting stage. This targeted water management significantly stimulated the accumulation of root abscisic acid (ABA), indole acetic acid (IAA), gibberellin (GA), and zeatin (ZT), which subsequently promoted root length density (RLD) in the 20–60 cm layer at anthesis. Meanwhile, MSI2 exhibited greater root vitality at filling and achieved the highest RLD at maturity. Driven by this optimized root system, MSI elevated leaf area index at anthesis and maintained higher post-anthesis flag leaf chlorophyll content; moreover, MSI2 further increased chlorophyll content during the late grain-filling stage. Consequently, compared with CI, MSI significantly increased post-anthesis dry matter accumulation and its contribution to GY, grain per spike and 1000-grain weight. Furthermore, MSI2 also showed higher GY than MSI1, and both exceeded CI by 11.56%–12.75% and 5.72%–6.18%, respectively. MSI significantly reduced water consumption from jointing to anthesis, while increasing water use during grain filling, thereby enhancing both GY and water use efficiency (WUE). MSI2 achieved the highest GY, WUE, plant nitrogen accumulation and nitrogen partial factor productivity. Overall, optimized micro-sprinkler irrigation can coordinate root and shoot development, delay leaf and root senescence, boost dry matter production, and ultimately realize synergistic improvement of GY and water-nitrogen use efficiency for wheat production in the HP.