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.