Soil aggregate stability is an important indicator for controlling soil losses and can improve soil quality, particularly in an area such as the Loess Plateau. The objective of this study was to estimate the differences in soil aggregates across six different land-use systems (grassland, apple orchard, abandoned apple orchard, cropland maize, cropland wheat, and shrub-grassland). For this purpose, dry and wet sieving techniques were employed to assess aggregate content and aggregate stability. Higher percentages of water stable aggregates were observed in the abandoned apple orchard and shrub-grassland at 63% and 61%, respectively. The maximum dry aggregate stability (%) was recorded at 78% and 77% in both wheat cropland and common apple orchard, and the abandoned apple orchard was only 74%. Both mean weight diameters and geometric mean diameters of aggregate were recorded as higher in grassland, shrub-grassland, and the abandoned apple orchard, than the other land uses. The formation of soil aggregates and their stability were positively correlated with soil organic carbon content and root biomass of different plant communities. Higher amounts of soil organic carbon content were noted in the abandoned apple orchard, common apple orchard, and natural grassland at the 0–20 cm soil layer. The results of the correlation coefficient showed a positive significant correlation between the mean weight diameter, geometric diameter, root biomass, and soil organic carbon content. Conclusively, the type of land use affected the soil aggregation and distribution of size fractions; the small fractions of the aggregates formed large fractions by combining with fresh organic matter, and increased soil organic carbon concentrations were closely linked with the formation of macro-aggregates. Thus, converting slope farmland to forestland and grassland could improve water-stable aggregate and reduce soil disturbances in areas (like the Loess Plateau) with the highest erosion risk.

Some agriculture practices are unsuitable in the northern hilly region of the Chinese Loess Plateau and have resulted in the degradation of the native vegetation ecosystems and unfavorable soil hydraulic properties, which cause serious soil losses. The objective of this study was to ascertain the influence of land use changes on soil infiltration rate and other related soil properties in this region. A total of 90 infiltration tests were run on six different land uses (natural grassland, apple orchard, abandoned apple orchard, farmland wheat, farmland maize, and scrub grassland). For studying the infiltration rate, a triplicate of infiltration tests had been taken using a disc permeameter with different pressure heads. Infiltration rate was high in abandoned apple orchard (10 mm min⁻¹) whereas very low in apple orchard (0.6 mm min⁻¹). The statistical analysis showed that the main soil properties were affected by changes of land use types or vegetation cover. Compared with that in the natural grassland and abandoned apple orchard sites, a notable reduction of soil root biomass, infiltration, and bulk density in apple orchard was recorded. The root image analysis showed that the natural grassland and abandoned apple orchard have strong root systems, that is, root length density 6.97 ± 0.344 cm cm⁻³, root surface area 1.56 ± 0.24 cm² cm⁻³, and average root diameter 0.814 ± 0.24 mm, in comparison with other sites. The limited root length density, root surface area, and average diameter were recorded in apple orchard 0.51 ± 0.03 cm cm⁻³, 0.49 ± 0.12 cm² cm⁻³, and 1.88 ± 0.24 mm. Conclusively, our study suggests that converting farmland apple orchard into grassland or scrubland may change soil hydraulic properties, which may help to reduce soil losses in the Loess Plateau.