Modified strip-tillage boosts maize grain yield and water use efficiency by enhancing fine root length in Northeast China’s black soil

Introduction: Soil moisture deficit limits crop productivity in rain-fed areas, and root system architecture and plasticity are closely related to water uptake and utilization. Methods: This study explored maize grain yield, soil moisture, root architectural plasticity, and their relationships with water use efficiency under modified strip-tillage (MST), no-tillage (NT), and conventional tillage (CT, as control) practices using two-year (2023-2024) field experiments in the black soil region of the Songliao Plain, China. Results: The results showed that compared with conventional tillage, grain yield increased by 13.32%-17.15% under no-tillage and 11.89%-16.06% under modified strip-tillage. Tillage practices significantly affected silking-stage root density (root length density, etc.), root morphology, and root diameter classes (e.g., < 0.5 mm). These root-related indices were higher under MST and NT than under CT, with no significant difference between MST and NT. Specifically, MST increased fine root length (root diameter, RD < 0.5 mm) by 93.23%-95.22% (vs. CT) and 39.90%-66.15% (vs. NT). The two conservation tillage treatments (MST and NT) increased the average soil moisture in the 0-40 cm layer during the growing season by 12.80%-31.43% and 11.44%-31.48%, respectively, compared with CT. Additionally, compared with CT, MST reduced water consumption by 1.95%-2.41% and increased water use efficiency by 16.33%-18.27%. Structural equation modeling showed that conservation tillage improved grain yield by optimizing root traits (e.g., root density, root morphology) and water use efficiency. MST performed better in these aspects, with its yield benefit attributed to the coordinated regulation of these traits.