Effect of straw mulching on sediment yielding process of soil with different initial water contents

Mulch with a layer of plant residue is an effective method for water and soil conservation. A laboratory experiment was conducted to evaluate the effect of antecedent soil moisture and straw mulching on sediment yielding process using rainfall simulator. The rainfall simulator was used to create rainfall intensity of 60 mm/h for 1 h. The study site was located at the ecological experimental research station of red soil, Chinese Academy of Sciences, in Yujiang County, Jiangxi Province of China. The soil used in this study was cultivated cambisol derived from red sandstone. The erosion plot was 12 m in length and 3 m in width with a slope of 9%. Antecedent soil moisture levels (dry, wet) and coverage degrees of straw mulching (0, 15%, 30%, 60% and 90%) were considered as two independent variables in this factorial design experiment. For the dry soils with the coverage degrees of 0, 15%, 30%, 60% and 90%, the average sediment yield rates within one hour was 24.5, 15.8, 10.4, 11.2, and 1.0 g/(m2?h), respectively. The sediment yield rates of the dry soils tended to increase slightly in the rainfall duration for a given percent ground cover. For the wet soils with the coverage degrees of 0, 15%, 30%, 60% and 90%, the average sediment yield rates with one hour were 115.6, 70.0, 49.6, 34.8, 31.9 g/(m2·h), respectively. Sediment yield rate of the wet soil decreased quickly during the simulated rainfall for a given percent ground cover. The average sediment yield rates in stable condition were 52.5, 30.5, 22.8, 19.8 and 15.4 g/(m2·h) with the coverage degrees of 0, 15%, 30%, 60% and 90%, respectively. The results indicate that coverage degree significantly affect sediment yield rate. Also, the coverage degree of 30% will effectively control runoff and soil loss.