Wheat straw reduces runoff, sediment yield and flow velocity in sloping farmland under two straw mulching methods

Aim The selection of suitable mulch methods is of great significance for obtaining the best soil and water conservation function of straw. Methods An indoor rainfall simulation experiment was conducted to analyze the straw effects on runoff, sediment yield and velocity under two straw mulching methods: straw surface mulch and straw incorporation. Under both methods, 4 straw rates (1.5, 2.5, 3.5, and 4.5 t center dot hm(-2)) and 3 straw lengths (3-5, 8-10, and 13-15 cm) were considered, and a bare slope was selected as the control. Results Compared with the straw surface mulch, there was a lower runoff reduction effect and a higher sediment reduction effect under the straw incorporation. The straw factor contributions to runoff and sediment varied with the mulching method. Compared with the surface mulch, the straw rate generated a higher sediment yield contribution and a lower runoff yield contribution under the straw incorporation. Moreover, the effect of straw length on the flow velocity under the straw surface mulch was greater than that under straw incorporation. Straw reduced the sediment yield mainly by lowering the erosion kinetic energy under the straw surface mulch, while straw could largely reduce the soil erodibility under the straw incorporation. Under the straw surface mulch, the best runoff and sediment reduction effects were achieved when the straw rate reached 4.5 t center dot hm(-2) and the straw length ranged from 3-5 cm. Under straw incorporation, the best effects were achieved when the straw rate reached 3.5 t center dot hm(-2) and the straw length ranged from 8-10 cm. Conclusions In areas with greater rainfall, straw incorporation should be incorporated. In areas with less rainfall, straw surface mulch should be used. This study provides a reference for the selection of suitable straw mulching methods and an understanding the mechanisms by which straw reduces soil and water loss, on sloping farmland.