Effects of Ridge Tillage and Straw Returning on Runoff and Soil Loss under Simulated Rainfall in the Mollisol Region of Northeast China

Abstract

Ridge tillage and straw returning are tillage practices widely used in the Chinese Mollisol region. However, the effects of ridge tillage combined with straw returning on runoff and soil loss control are still unclear. The objective of this study was to compare the effects of ridge tillage practices (contour ridge (CR)) and longitudinal ridge (LR), straw returning practices (straw on the furrow surface (SS)) and straw below the furrow (SB)), and their interactions on the runoff and soil loss by using simulated rainfall experiment. Two rainfall intensities (45 and 60 mm h−1) were applied to six combinations of ridge tillage and straw returning (contour ridge treatment, contour ridge with straw on the furrow surface treatment, contour ridge with straw below the furrow treatment, longitudinal ridge treatment, longitudinal ridge with straw on the furrow surface treatment, and longitudinal ridge with straw below the furrow treatment) on a 5° slope. The results showed that the phenomenon of ridge failure was common in the treatments with contour ridge. The average runoff rate and soil loss rate after ridge failure for treatments with contour ridge were separated 2.8 and 3.5 times greater than those of before failure at 60 mm h−1. However, the corresponding values were only 68.6% and 43.3% of the average value of longitudinal ridge treatment and longitudinal ridge with straw below the furrow treatment at 60 mm h−1. The water storage capacities of treatments with contour ridge remained constant when the rainfall intensity varied. The water storage capacities of contour ridge with straw on and below the furrow treatments were separate 3.0 and 1.0 mm less than that of contour ridge. However, longitudinal ridge with straw on the furrow surface treatment increased the runoff rate by 7.4% but reduced the soil loss rate by 72.6% when compared with longitudinal ridge treatment and longitudinal ridge with straw below the furrow treatment under the two rainfall intensities. Longitudinal with straw on the furrow surface treatment was more conducive to the stability of ridges, and there was no significant difference in total soil loss between longitudinal ridge with straw on the furrow surface treatment and treatments with contour ridge. This study was based on simulated rainfall conditions, and its adaptability under long-term positioning monitor in the field should be added in future.