Effect of straw-incorporation into farming soil layer on surface runoff under simulated rainfall

Abstract

Returning crop straw into farmland is an important application and effective soil amendment method as it can increase soil organic matter to improve soil fertility and crop yield. In addition, this practice can help retain soil moisture and slow down the rainfall runoff rate, particularly on sloping farmland. This study uses laboratory experiments with a silt loam soil to examine the effects of wheat straw incorporation into cultivated farmland soil on rainfall-runoff. The experiments involved four straw incorporation rates (0 (control), 2, 4, and 8 t/ha), three rainfall intensities (80, 120 and 160 mm/h) and three slope gradients (10, 15 and 20°), carried out by a completely randomized combination design, with three repetitions. In all the experimental runs, the total rainfall amount was 100 mm per event. Our experimental results showed that the duration of runoff initiation time at straw incorporation rates of 2, 4 and 8 t/ha were increased by 1.63% to 104.93%, 6.16% to 111.67% and 15% to 141.25%, while the total runoff amounts decreased by 11.74% to 28.81%, 24.21% to 49.67% and 38.90% to 65.93%, compared with those of our control group (0 t/ha). The effects of straw incorporation on the runoff initiation delay time and runoff reduction were significant, particularly when the rainfall intensity was 120 mm/h and the slope was 10°. With increases in rainfall intensity and slope gradient, the runoff initiation time durations were decreased and the runoff rate increased. In conclusion, incorporating wheat straw into the farmland soil can delay the runoff initiation time and reduce runoff volume, to significantly increase rainwater storage into soil, thereby increasing the rainwater utilization rate and to benefit soil erosion control. This study can provide a data basis for farmland soil and water conservation research and practice.