Variation in soil detachment capacity of structural and sedimentary crusts induced by simulated rainfall formed on ridge and furrow

Abstract

The response of erosion to soil physical crusts (i.e., structural and sedimentary crusts) has been extensively investigated. Yet few studies have quantified the effects of physical crusts on their detachment capacity (Dc). Accordingly, we investigated the variation in Dc of physical crusts as induced by simulated rainfall. The runoff plot (2.0 m long × 1.0 m wide × 0.5 m high) was set to a slope of 5° and filled with Lou soil (Haplic Luvisol) using horizontal tillage with ridges (1.0 m long × 0.2 m wide × 0.1 m high) and cm furrows (1.0 m long × 0.3 m wide × 0.1 m deep). Simulated rainfall was applied at a single intensity (60 mm h−1) for seven durations (0, 5, 10, 15, 20, 25, and 30 min) to obtain structural (at ridges) and sedimentary (at furrows) crusts. Crust samples were collected to obtain Dc, by scouring them for 2 min at a constant inflow discharge (0.8 L min−1) on a hydraulic flume (15° slope). For both structural and sedimentary crusts, with increasing rainfall duration, the measured bulk density (BD), crust thickness (Ct), micro-aggregate content (MIA), and disintegration index (DI) increased, whereas the macro-aggregate content (MAA) decreased. Dc of 0 min and structural crust formed within 5 min of rainfall decreased with a longer scouring time. By contrast, Dc of the other crust types initially rose with an extended scouring time but then plateaued after ∼ 60 s. Dc of sedimentary crusts were significantly lower than that of structural crusts. Notably, crusts formed by rainfall at 30 min had greatest detachment reduction benefit. Dc was inversely related to BD, Ct, MIA and DI, whereas increased with increasing MAA. This research provides a timely reference for the effect of physical crust on concentrated flow in arid and semi-arid areas.