Spatial distribution characteristics of ridge plant belts on soil water-holding capacity and soil structure in sloping farmland

This study aims to clarify the spatial distribution characteristics of ridge plant belts on soil water-holding capacity and soil structure in sloping farmland, providing a scientific basis for optimizing ridge plant belt configurations and soil and water conservation measures in Northeast China's black soil region. Sloping farmland with ridge plant belts was selected as the research object (Ridge 1: ridge spacing of 12.5 m; Ridge 2: ridge spacing of 19.5 m), and sloping farmland was selected as the control. Soil samples were collected at uniform spatial intervals from both sloping arable land with ridge vegetation strips and the control area to measure key soil properties in the surface layer (0–15 cm), and to quantify the differences in the spatial distribution characteristics of soil water-holding capacity and soil structure in sloping farmland with different spacings of ridge plant belts.  (1) Compared to the control, the sloping farmland with ridge construction showed a significant increase in total porosity, capillary porosity, saturated water holding capacity, field capacity, and capillary water holding capacity, with a relatively uniform distribution across the slope with ridge. In addition, compared to the sloping farmland with ridge 2, the soil on the sloping farmland with ridge 1 showed an increase of 0.96-1.11 times in total porosity, 1.21-1.31 times in capillary porosity, 1.03-1.25 times in saturated water holding capacity, 1.22-1.78 times in field capacity, and 1.33-1.52 times in capillary water holding capacity, respectively. (2) The soil mechanical stable aggregate content, MWD (mean weight diameter), water-stable aggregate content, and GMD (geometric mean diameter) in the sloping farmland with ridge showed significant improvements across all fields. Compared to the controls, the sloping farmland with ridge increased by 1.01-1.15 times, 0.94-1.61 times, 1-1.17 times, and 1.05-1.55 times, respectively. This indicates that the sloping farmland with ridge effectively improves soil structure compared to the control. Moreover, compared to the sloping farmland with ridge 2, the soil mechanical stable aggregate content, MWD, water-stable aggregate content, and GMD in the sloping farmland with ridge 1 increased by 1.08-1.14 times, 0.95-1.28 times, 1.07-1.15 times, and 1.14-1.40 times, respectively. Constructing ridges can improve water retention capacity structure characteristics of soil,with a more significant improvement effect observed in relatively small distances smaller distances between ridges, providing a scientific basis for the optimization of water and soil conservation measures for ridge and vegetation belts and sloping cultivated land in the black soil area of Northeast China. The construction of ridges on sloping farmland can improve the soil water-holding capacity and soil structural characteristics. In this study, sloping farmland with a smaller ridge spacing demonstrated a more significant improvement in soil quality. This research provides a scientific basis for optimizing water and soil conservation strategies in the black soil region of Northeast China, emphasizing the importance of ridge spacing in enhancing soil quality and water retention capacity in sloping farmland.