5 Conclusions

It was extremely difficult to establish a functional relationship between the magnitude of yield reduction and soil erosion depth, because the relationship varied across regions. Based on a meta-analysis of experiment studies on relationships between crop yield and depth of soil erosion at global-scale, we demonstrated that a general relationship of crop yield response to soil erosion was achievable, and we conclude that crop yield was negatively affected by soil erosion. Slight erosion (erosion depth < 5 cm) had no significant effects on crop yield. The effect degree of erosion was significantly different between 5 - 10 cm and 10 - 15 cm erosion depth intervals. When erosion depth was > 20 cm, crop yield was clearly decreased no matter what soil management measures were adopted, which indicated that the degradation of soil productivity could not be restored. Thus, the results presented in this paper suggested that a linear relationship does not well describe the relationships of crop yield and soil erosion because the response of crop yield to erosion is most severe between 5 cm and 15 cm. Effective soil remediation, and soil and water conservation measures need to be established to maintain soil thickness, protect soil resources, and minimize effects of soil erosion. Furthermore, soil that has been eroded but is still in production requires special attention.