Rainstorm events increase risk of soil salinization in a loess hilly region of China

Abstract Soil salinization is widespread and it hinders agricultural development in the loess hilly region of China. In this study, we determined the dynamic distribution of the soil salinity (SS) as well as its effects on maize (Zea mays L.) after rainstorm events in two land types produced by excavation and sediment deposition. Four treatments were tested comprising sediment deposited farmland without plastic mulch (S1) and with plastic mulch (S2), and excavated farmland without plastic mulch (E1) and with plastic mulch (E2). The results showed that the dynamic distribution of the SS exhibited similar characteristics included leaching, rapid accumulation, and relatively stability in the 0–40 cm soil layer after rainstorm events. A turning point where the leaching and accumulation of SS reached a balance in the 0–40 cm layer occurred on about the 4th day under the no plastic mulch treatments and on the 6th day under the plastic mulch treatments. The SS reached a relatively stable condition in the whole soil layer on the 12th day. Rainstorm events increased the accumulated SS by 0.36, 0.08, 0.44, and 0.20 g kg–1 under E1, E2, S1, and S2, respectively, during the year. Plastic mulch treatments decreased the average accumulated SS by 66.7% and the average SS by 22% by reducing water infiltration and soil evaporation. The average SS and accumulated SS in sediment deposited farmland were 8.9% and 47.6% higher, respectively, than those in excavated farmland because of the lower depth of the groundwater influence zone and more abundant capillary pores in the sediment deposited farmland. The average SS in the whole soil layer followed the order of: S1 (0.72 g kg–1) > E1 (0.62 g kg–1) > E2 (0.53 g kg–1) > S2 (0.52 g kg–1) (P