Effect of surface rills on soil redistribution by tillage erosion on a steep hillslope

Water and tillage erosion processes are important contributors to the total soil erosion in steeply sloping farmland. Although these erosion processes and mechanisms are well understood separately, little is known about the impact of water erosion on the soil redistributed by tillage erosion on sloping fields. In this study, the magnetic tracing (MT) and terrestrial laser scanning (TLS) techniques were applied to perform tillage simulation experiments to ascertain the effect of surface rills on tillage erosion in the dry-hot valley region of southwestern China. The results of simulation experiments indicate that the mean soil flux (Qs) due to tillage on the single-rilled (double-rilled) hillslopes was 85.6 (109.9) kg/m for the mean soil loss rates (Rs) of 21.0 (53.7) Mg/ha in simulated-rill areas, and that tillage erosion rates (Rt) tended to increase with increasing Rs. Rt of the single-rilled (double-rilled) hillslopes increased by 1.7 (2.2) times averagely, compared with those of the non-rilled hillslopes. The greater the number and volume of rills, the more easily soil translocation occurred on steep slopes. Rt were highly significantly and positively correlated with Rs on the rilled hillslopes (P < 0.01). As slope gradient increased, the tillage displacement and Qs appeared to increase on the single-rilled hillslopes. A comparison of measurement results showed that the TLS technique was not only able to measure tillage-induced soil translocation with an accuracy similar to that of the MT technique, but also captured the change in the slope microtopography due to tillage operation. Our results indicated that surface rills remarkably influence tillage erosion and that Qs and Rt enhance with increasing Rs on the slopes.