Scale effect on runoff and soil loss control using rice straw mulch under laboratory conditions

Abstract. Amendments can control the runoff and soil loss by protecting soil surface. However, scale effects on runoff and soil loss control has not been considered yet. The present study has been formulated to determine the efficiency of two plot sizes of 6 and 0.25 m2 covered by straw mulch with rate of 0.5 kg m−2 in changing the time to runoff, runoff coefficient, sediment concentration and soil loss under laboratory conditions. The study has been conducted for a sandy-loam soil taken from summer rangeland, Alborz Mountains, Northern Iran under simulated rainfall intensities of 50 and 90 mm h−1 and in 3 replicates. The results of the study showed that the straw mulch had more significant effect in in reducing runoff coefficient, sediment concentration and soil loss at 0.25 m2 plot scale. The maximum effectiveness in time to runoff for both the scales, observed in rainfall intensity of 90 mm h−1. The maximum increasing and decreasing rates in time to runoff and runoff coefficient observed in the rainfall intensity of 90 mm h−1 with the amounts of 367.92 and 96.71% for 0.25 m2 plot and the amounts of 110.10 and 15.08% for 6 m2 plot respectively. The maximum change of soil loss in both the intensities of 50 and 90 mm h−1 occurred at 0.25 m2 plot with the amount of 100% whereas at 6 m2 plot, decreasing rates of soil loss for in both the intensities of 50 and 90 mm h−1 were 46.74 and 63.24%, respectively.