Enhancing Root Growth and Water Use Efficiency of Winter Wheat by Optimizing the Irrigation Amount of Micro-Sprinkler Irrigation

Conventional irrigation practices, characterized by excessive water application, have diminished water use efficiency (WUE) and intensified agricultural water consumption. Optimizing irrigation schedules and moderately reducing water input are therefore essential for enhancing WUE while safeguarding stable yields. Micro-sprinkler irrigation, which integrates the benefits of both drip and sprinkler systems, represents a promising technology with substantial water-saving potential. However, its effects on root development and crop yield remain inadequately investigated. Here, we established three micro-sprinkler irrigation regimes—MS20 (20 mm), MS30 (30 mm), and MS40 (40 mm)—alongside flood irrigation (FI) and rainfed (RF) controls, to systematically assess their impacts on soil water content, root growth traits, dry matter accumulation, yield, and WUE. Compared with FI, MS treatments decreased profile soil water content at jointing but increased it in specific layers during grain filling, albeit to varying extents. MS treatments enhanced total root length density (TRLD) and total root dry weight density (TRDD) relative to FI, with MS20 significantly increasing both parameters in the 20–100 cm soil layer. Moreover, MS20 increased pre-flowering dry matter translocation (PDMT) by 9.69% on average and post-flowering dry matter accumulation (PFDMA) by 15.04% during the 2022–2023 season. Yield and WUE under MS treatments exceeded those under FI by 3.46–6.53% and 4.42–21.21%, respectively. Among the MS treatments, MS20 achieved the highest average WUE. No significant yield or WUE differences were observed between MS20 and MS30, with MS30 producing the numerically maximum average yield. MS40 did not significantly affect yield in 2021–2022; however, it substantially reduced both yield and WUE relative to MS20 and MS30 in 2022–2023. A comprehensive TOPSIS analysis identified the combination of micro-sprinkler irrigation with total seasonal irrigation amounts of 80 mm or 120 mm as the optimal strategy for winter wheat production in the eastern Henan region of the North China Plain (NCP).