Gravel mulching effects on soil physicochemical properties and microbial community composition in the Loess Plateau, northwestern China

Gravel mulch has been used as an agricultural water conservation measure for over three hundred years in China's semiarid regions. In this study, a 3-year gravel mulch experiment on slopes in the northwestern Loess Plateau was conducted to evaluate the impact that different sized gravel mulch and natural rainfall has on surface runoff, soil physicochemical properties and microbial communities. The following three treatments were investigated: small-sized gravel mulch (AG, 2–5 mm particle size), large-sized gravel mulch (BG, 40–60 mm particle size), and no gravel mulch as a control (CK). We found that gravel mulch could effectively control surface rainwater runoff, especially in the AG treatment. AG treated soil was typically oligotrophic compared to BG treated soil with higher soil carbon and nitrogen content.