A new method to calculate soil loss tolerance for sustainable soil productivity in farmland

Abstract

Soil loss tolerance (T) is a widely used concept for assessing potential risks of soil erosion and is a criterion for assessing the effectiveness of soil and water conservation projects. However, current approaches for calculating T values lack a strong scientific basis, and few practicable methods are available. Many questions remain regarding which parameters, such as planning periods and offset damages, should be included in calculating T values. Here, we developed a new method to calculate soil loss tolerance as a function of the soil productivity index (SPI) for farmland. To achieve sustainable soil productivity in farmland, erosion rates leading to SPI values lower than the lower boundary of soil productivity (SPI0) are not tolerable and must be controlled by soil conservation measures. We applied this method in the Red River Basin of China based on the investigation of typical soil profiles and crop yields. Our results show that the T values in the Red River Basin ranged from 0.91 to 10.24 t ha−1 a−1. The SPI0 and the lowest limit of soil loss tolerance (T1) were 0.4 and 0.91 t ha−1 a−1, respectively. Here, we demonstrate that, when determining T values in farmland, (1) the soil formation rate and offset damage should not be core items, (2) the “planning period” concept should be replaced by “sustainability”, (3) the management objective of T should be the sustainability of the soil resource, and (4) the T values of farmland should be determined according to soil productivity. We provide a reasonable and feasible method to determine T for farmland, which will help maintain the sustainability of soil productivity.