Restoration of Grassland Improves Soil Infiltration Capacity in Water-Wind Erosion Crisscross Region of China’s Loess Plateau

Soil water infiltration is a key mechanism for meeting plant water demand and groundwater recharge cycles; however, unreasonable land use practices cause reduced infiltration capacity and greater soil erosion. To date, differences in the properties of aeolian sandy soil and Pisha sandstone soil under different utilization methods as well as in soil properties, aggregates, and infiltration among kind of soil types, remain poorly understood. In this work, 54 soil samples of cropland and grassland were selected to identify the unique characteristics of soil infiltration processes under transition from cropland to grassland and contributions of soil properties to soil infiltrability in the Loess Plateau of China. The results showed that converting cropland to grassland could enhance the stable infiltration capacity of shallow soils of aeolian sandy soil and loess soil by 43.6% and 35.7%, respectively. Compared with cropland, the root properties and soil aggregate formation of the three soil types increased during grassland use, with the largest increase in soil organic matter content (32.14%) and total porosities (6.4%). As determined by the ring knife method, the saturated infiltration capacity of Pisha sandstone soil was significantly lower than in aeolian sandy soil and loess soil (p < 0.5). Moreover, its saturated infiltration capacity of cropland was better than grassland. Spearman’s correlation analysis and structural equation modeling (SEM) revealed that soil infiltration capacity appeared to be the most influenced by soil organic matter, and aggregate structure. These results highlight that fifteen years of returning cropland to grassland is not enough to affect the infiltration ability of deep soil (≥20 cm), and this improvement requires longer term maintenance.