Response of seasonal variation in soil detachment capacity to straw incorporation in sloping farmland on the Loess Plateau

Soil detachment capacity by rill flow (Dc) is sensitive to changes in topsoil properties generated by crop straw incorporation. In the present study, we investigated the effect of crop straw incorporation on the seasonal variation in Dc, the knowledge regarding which is limited currently, and identified the key influencing factors. Three typical crop straw types (wheat, soybean, and maize) were selected for this study. Soil samples incorporated with crop straw and without crop straw were collected over 375 days (from October 1, 2020 to October 10, 2021) and were subjected to a hydraulic flume (length, 4.0 m; width, 0.2 m) to determine Dc. The topsoil properties soil bulk density (BD), soil cohesion (Coh), soil penetration resistance (PR), soil organic matter content (SOM), mean weight diameter (MWD), and straw decomposition rate (SDR) were measured to explain the seasonal variation in Dc. The results showed that crop straw incorporation effectively reduced Dc, and the Dc for the soil incorporated with straw decreased by 25.92%-38.76% compared with that without straw incorporation. Dc exhibited a significant decreasing trend over time, and the Dc at the end stage decreased by 83.00%-88.31%, compared with the initial stage. Seasonal variation in Dc was significantly correlated with BD, Coh, PR, SOM, MWD, and SDR. The measured Dc decreased with BD and Coh as a power function and with SOM and MWD as an exponential function. The influence of straw incorporation on Dc is time-dependent and can be divided into short-term and long-term effects. Natural soil consolidation gradually masked the effect of straw residue with the decomposition of the incorporated straw. The comprehensive response of seasonal variation in Dc to straw incorporation was described by a power combination equation (Dc = 1.23 tau(1.65) BD-2.63 Coh(-1.33) SOM-0.70; R-2 = 0.96). Thus, the seasonal variations in Dc with straw incorporation were mainly controlled by the changes in soil properties triggered by the decomposition of incorporated straw and natural soil consolidation. The results of this study provided a scientific reference for soil erosion prediction and control in sloping farmlands.