Combined effects of the wheat straw length and incorporation rate on reducing runoff and sediment yields

Abstract

Straw incorporation is a critical conservation tillage measure that effectively reduces slope runoff and sediment. This study used laboratory experiments to examine the combined effects of the straw length and incorporation rate on reducing runoff and sediment, under straw incorporation. The experiments involved three wheat straw lengths (3–5, 8–10, and 13–15 cm) and four incorporation rates (1.5, 2.5, 3.5, and 4.5 t·hm−2). Bare slopes were selected as the control, and the experimental soil was silty loam. Three hundred-cm-long, 100-cm-wide, and 50-cm-deep soil tanks with 15° slopes were subjected to artificial rainfall with a duration of 1 h and an intensity of 90 mm·h−1. Straw incorporation reduced the runoff and sediment yields by 3.11–18.18% and 30.71–57.71%, respectively. When the straw length was combined with the incorporation rate, as the straw length increased, the sensitivity of the runoff and sediment yields to the incorporation rate decreased first and then increased. Similarly, the sensitivity to the straw length also decreased first and then increased, as the incorporation rate increased. In the combination mode, the greatest runoff and sediment reduction effects were achieved at a straw length of 8–10 cm and an incorporation rate of 3.5 t·hm−2, which were the optimal straw length and incorporation rate values. The reduction effect of the straw length on the runoff and sediment yields was weaker than that of the incorporation rate. The incorporation rate was always the main factor affecting the runoff yield during the erosion process, while the main factor affecting the sediment yield changed gradually from the straw length to the incorporation rate. Thus, the incorporation rate is also a crucial factor inhibiting rill development. The effect of the straw length on sediment reduction primarily involves reducing hydrodynamic factors, such as flow velocity, while the incorporation rate plays a stronger role in reducing soil erodibility. This study provides a scientific basis for selecting and applying conservation tillage measures involving straw incorporation.