The Sealing Process and Crust Formation at Soil Surface under the Impacts of Raindrops and Polyacrylamide

摘要

Soil seals and crusts are formed at soil surface due to the impacts of raindrops and break of aggregates. They can significantly reduce soil infiltration rate and subsequently lower the utilization of water resources, and increase runoff, which induces soil erosion. To understand the processes of seals and crusts, experiments were conducted with rainfall simulation under laboratory conditions. The experiments involved different rainfall intensities (50 mm · h~(-1), 100 mm · h~(-1), 150 mm · h~(-1)), slopes (8.74%, 17.63%, 36.4% and 46.63%) and surface treatments (one control and three PAM coverage rates: (A > B > C)). Comparing the micromorphology, with the aid of scanning electron microscopy (SEM), of soil surface layer of control with PAM treatments', it can be concluded that soil crust is formed by depositional and structural crust. The curves of infiltration for different treatments as a function of time show that crust have four forming statuses.