Characteristics of soil comprehensive anti-erodibility under sloped cropland with hedgerows

Abstract: Soil shear strength (SS), anti-erodibility (AE), and anti-scouring (AS) not only reflect strength of soil confronting water erosion in different developmental stages (raindrop erosion, sheet erosion by sheet flow, gully erosion of streams), but also decide comprehensive ability of soil confronting water erosion by their coexistence and coupling. Hedgerow patterns have been used as one of controlling techniques for agricultural non-point pollution (especially nitrogen and phosphorus loss of farmland). At present, research studies on effect of hedgerow patterns controlling soil and water, nitrogen, and phosphorus loss are extensive. However, soil comprehensive anti-erodiblity (CAE), one of their internal causes, is hardly discussed. Soil AE, including SS and AS, is called soil CAE in this paper. Taking sloped farmland in central Sichuan as the research subject, based on a long-term experiment on the effect of hedgerows controlling soil and water loss, characteristics of soil CAE were studied with mathematical statistics in this paper to provide a research basis for the mechanism of hedgerow patterns controlling soil, water, nitrogen, and phosphorus losses. Results show that soil AE and CAE of hedgerow-crop patterns were higher than that of the conventional contour pattern. The soil AE index (AEI) for the Amorpha (T1), Vetiver (T2), Alfalfa (T3) and Eulaliopsis binata (T4) patterns increased by 3.99、2.65、3.13、and 2.36, respectively. The soil CAE index (CAEI) for the T1, T2, T3, and T4 patterns increased by 102.9%, 91.9%, 87.9%, and 82.9%, respectively. Therefore, in terms of CAE, the order of the effect of different hedgerow patterns increasing soil CAE was Amorpha > Vetiver in 20o slope farmland, Alfalfa > Eulaliopsis binata in 13o farmland. Compared with conventional contour crop patterns, hedgerow and crop belt soil AE and CAE of sloped farmland in each slope position were improved under hedgerow-crop patterns, especially hedgerow belts. Hedgerow-crop patterns weaken considerably the conditions that soil AEI and CAEI decreasing by nearly line from low slope to top slop, which improved excessive slope heterogeneity of soil AE and CAE in slope farmland. Under hedgerow-crop patterns, soil AE and CAE were significantly or apparently increased because of multiple hedgerow belts improving soil physicochemical properties (such as the increasing soil clay content and organic matter), and multiple effects (such as the consolidation and frictional effects) of hedgerow roots. The paper is to provide a research basis for exploring how hedgerow patterns control the loss of soil, water, nitrogen, and phosphorus and eventually other pollutants.