Long-term manure fertilization increases rill erosion resistance by improving soil aggregation and polyvalent cations

Application of organic fertilizers is a potential practice to prevent soil erosion by changing the physicochemical properties of the soil, such as macroaggregates, soil organic carbon (SOC) content, and exchangeable cations. However, the practical performance of organic fertilizer in soil erosion after a long-term application has scarcely been reported. To reveal the response of soil erosion resistance (i.e., the soil susceptibility to resist external erosion force) to 43 years of organic fertilization, five treatments were investigated: (1) CK (no fertilizer), (2) NPK (mineral fertilizer), (3) M (pig manure), (4) MN1 (pig manure + 138 kg N ha -1), and (5) MN2 (pig manure + 276 kg N ha -1). The results showed that NPK, M, MN1, and MN2 significantly increased soil critical shear stress (tau c) by 54 %, 87 %, 101 %, and 67 %, respectively, compared to CK. However, rill erodibility (kd) was increased significantly only in the MN2 treatment. The optimal partial least squares regression model showed that the increase in soil exchangeable Ca2+ was the dominant contributor to the tau c increase, while soil mean weight diameter (MWD) had the greatest negative effect on kd. Compared with CK, the soil exchangeable Ca2+ in M and MN1 increased significantly by 123 % and 135 %, respectively. The MWD in M and MN1 increased by 86 % and 83 %, respectively, compared with that in CK. The application of pig manure was beneficial for decreasing exchangeable Na+ and increasing SOC content, which could improve MWD. Manure with a high N content did not increase MWD due to SOC decomposition. Our results indicate that the long-term application of manure, alone or combined with moderate N, improves rill erosion resistance.