Ridge and contour tillage effects on soil erosion from steep hillslopes in the Sichuan Basin, China

Abstract

Little is known about the impact of tillage methods on soil movement resulting from hoeing tillage operations in the Sichuan Basin, China. Effects of tiered ridge and contour tillage on soil movement (translocation and erosion) were examined in the steep hillslopes of this basin using a physical tracer method. Stone chips were used as tracers, having a contrasting color from the surrounding soil, and were incorporated into each experimental plot. Net mean downslope displacement distance by contour tillage was much shorter (P<0.0001) than that by downslope tillage (5 times for tiered ridge tillage, 3 times for flat tillage). Soil displacement distance was positively correlated to slope gradient for downslope tillage (R2 = 0.6303 – 0.8282, P = 0.0002 – <0.0001), whereas slope gradient was not significantly correlated to soil downslope displacement by contour tillage (R2 = 0.2421-0.3142, P = 0.0529-0.0239). Tillage transport coefficients were 25.5 and 30.7 kg m−1 tillage pass−1 for k3-values and 153.0 and 141.3 kg m−1 tillage pass−1 for k4-values, respectively for downslope ridge and downslope flat tillage. For a typical downslope length of 15 m and two tillages per year, tillage erosion rates by downslope tillage reached 42.0 - 129.1 t ha−1 yr−1 and 49.0 - 122.1 t ha−1 yr−1 for slopes ranging from 0.04-0.47 m m−1 and from 0.04-0.43 m m−1 respectively for downslope ridge and downslope flat tillage. Tillage erosion rates by contour tillage were reduced by 84% and 77%, compared to downslope tillage respectively for ridge and flat treatments. No significant differences in soil translocation and erosion rates existed between downslope ridge and downslope flat tillage. Contour ridge tillage was more effective than contour flat tillage with respect to controlling tillage translocation and erosion.