Soil loss tolerance in calcareous soils of a semiarid region: evaluation, prediction, and influential parameters

Abstract

AbstractPredicting soil loss tolerance (T‐value) as a first and crucial step in assessing soil erosion using pedotransfer functions (PTFs) could save time and cost. Therefore, this study aimed to evaluate T‐value and its influential parameters for calcareous soils of the Dorudzan Watershed, Fars Province, Iran, and to develop PTFs for its prediction using easily measureable soil properties. T‐value was determined in 60 soil profiles based on the soil thickness method. Various basic soil properties were used to develop five PTFs using stepwise multiple linear regression. T‐value varied from 3.5 to 22.5 with a mean value of 10.4 t ha−1 yr−1, which is approximately equal to the proposed value by US Department of Agriculture (11 t ha−1 yr−1). T‐value in Inceptisols located in the dam shore and agricultural lands was significantly higher than that of Entisols located in the forest and rangelands. Organic matter (OM) with a correlation coefficient of .77 with T‐value was the most influential variable in prediction of T‐value. The PTF 5, which used OM, soil aggregate stability, and permeability, with the highest R2 (0.72 and 0.79), the lowest mean error (−0.44 and 1.75 t ha−1 yr−1), the lowest root mean square error (2.98 and 2.75 t ha−1 yr−1) and the minimum Akaike information criterion (51.1 and 17.2) provided the best predictions for T‐value. However, when considering the acceptable indices and easier measureable soil properties (OM, soil erodibility, and pH) in PTF 3, we concluded that it was the best model to predict T‐value. Generally, the application of thickness method is recommended to determine T‐value in semiarid regions.