Influence of gully erosion on hydraulic properties of black soil-based farmland

Gully erosion is a severe form of water erosion worldwide. However, the influence of gully vicinity on the soil hydraulic properties has been poorly studied, hindering the understanding of their effect on crop yields. Therefore, this study hypothesizes that gully vicinity influences farmlands and aims to determine the mechanism of their influence on soil hydraulic properties and crop characteristics. The soil properties from nine gullies in cultivated lands inclined at1%, 2%, and 3% in three latitudinal regions were determined at the gully edge (EG0) and 50 m further the edge into the farmlands (EG50) at the following gully units: head, mid-upper, mid, mid-lower, and tail. Soil hydraulic properties (bulk density, saturated hydraulic conductivity, and water retention), soil penetration resistance, and soil organic matter were analyzed. The study findings indicate that the gully existence affected the soil properties at diverse range of intensities. The total-available water content (θ30 - θ1500), the ratio of more-available water to total-available water content (θ30-θ330)/(θ30-θ1500), saturated hydraulic conductivity, and soil organic matter were lower, but the bulk density and soil penetration resistance were higher at EG0 compared with those at EG50. The (θ30-θ330)/(θ30-θ1500) ratio in the gully vicinity was considerably lower in our study than in previous studies, indicating gully erosion substantially deteriorated the hydraulic properties. The differences in soil hydraulic properties between EG0 and EG50 were more evident in higher latitudinal region and in steeper farmlands. In addition, the lower soil organic matter and higher bulk density probably led to a 3–11% decrease in crop yield at EG0 than at EG50. In summary, this study indicates that gully erosion affects farmland not only at its boundaries but also further into its surroundings. Accordingly, managements suited to the hydraulic properties of the gully-surrounded areas may be implemented to maximize the crop yield of farmlands.