To determinate tillage erosion rate and hydraulic erosion rate of purple soil under different slope gradients

a series of simulated tillage experiments (5

10

and 15 operation tillage) were conducted on 5°

10°

and 20° slope farmlands

respectively. Then a series of scouring experiments with water discharge of 60 L/min were carried out on those slopes. Close-range photogrammetry technology was used to monitor the landform changes of purple slope farmland

and the high resolution digital elevation models (DEMs) were generated to calculate the net soil loss volume. Meanwhile

erosion pins were used to verify the accuracy of close-range photogrammetry technology by measuring the depth variation of soil layer

and the erosion rate and hydraulic erosion rate of purple slope farmland under different slope conditions were calculated. Results showed that the close-range photogrammetry technology was reliable and efficient to monitor landform changes and calculate the soil erosion rates. The calculated results of DEMs were similar to those of erosion pins. The average tillage erosion rates were 69.85

131.45 and 155.34 t/(hm2·tillage pass) on 5°

10° and 20° purple slope farmland

respectively

and tillage erosion rate showed an increase trend with the increasing of slope gradient

while it decreased with the increasing of tillage intensity. The average hydraulic erosion rates were 1 892.52

2 961.76 and 4 405.93 t/(hm2·h) on 5°

10° and 20° purple slope farmland

respectively. Hydraulic erosion rate was positively related to the slope gradient. Meanwhile

hydraulic erosion rate showed an increase trend with the increasing of tillage intensity

indicating that tillage erosion would accelerate the hydraulic erosion. These results could provide technical support and data foundation to the studies about soil erosion in purple slope farmland under tillage erosion and hydraulic erosion.