Impacts of Gravel Mulch on Sediment Yield Process under Simulated Rainfall Conditions

Abstract

Abstract: In agricultural practice of arid and semiarid regions, gravel mulch on soil surface is used to increase rainwater infiltration, reduces surface runoff and soil erosion, and protects natural environment while increase agricultural productivity. Gravel mulch has great impacts on soil surface conditions to affect rainwater infiltration and surface runoff processes, as well as sediment yield process. A series of laboratory experiments were conducted to investigate the impacts of gravel mulch of different sizes on soil infiltration-runoff processes under different rainfall intensities and slope gradients with a laboratory rain simulator and portable runoff flumes. The experiments involved 3 rainfall intensities (60, 90, 120 mm/h), 2 slope gradients (0°and 10°), and 4 surface mulches (gravel size of 0.5, 2.5, and 5.0 cm, and control). Runoff samples were collected at 5-minute intervals after runoff generation for runoff and sediment determination. The sediment in runoff samples were weighed with laboratory electronic balance after ovendried in drying oven at 105 centigrade. The results indicated that gravel mulch affected significantly the sediment yield process, in terms of sediment content, detachment rate and cumulative sediment. Gravel size was the most influencing factor. Gravel mulch of smaller size produced less sediment yield. Rainfall intensity and slope gradient were secondary influencing factors on sediment yield as compared with gravel size. The results help to understand the mechanism of gravel mulch for reducing sediment yield and preventing soil erosion so as to benefit dry-land farming practice and protect the environments.