Determination of the threshold velocity of soil wind erosion using a wind tunnel and its prediction in calcareous soils of Iran

Determination of the threshold velocity (TV) is a crucial step for wind erosion evaluation. Due to the difficulties of direct field measurements, pedotransfer functions (PTF) and easily measurable soil properties could be used to save time and cost in predicting TV. Therefore, the present study was conducted to predict the TV using pedotransfer functions and to assess its influential parameters in calcareous soils of Fars province, southern Iran. To this end, the TV was measured by a portable wind tunnel at 72 locations in different land uses and soil types across the study site. Various physicochemical and mechanical soil properties were used to develop six pedotransfer functions using multiple linear regression. Results showed that the TV varied from 3.0 m s-1 in poor rangelands to 12.83 m s-1 in saline lands. Soil surface shear strength with a correlation coefficient of 0.85 was the most influential parameter affecting the TV, followed by aggregate mean weight diameter (MWD). Results of the predictive models revealed that PTF 5, which was developed using shear strength and penetration resistance (R2 = 0.86, RMSE = 0.85 m s-1), and PTF 6, which was developed using MWD and penetration resistance (R2 = 0.81, RMSE = 1.07 m s-1), had the highest performance for predicting the TV. PTF 5 was selected as the final model for predicting the TV since it only needed easier measurable mechanical soil properties without soil sample collection. We concluded that the use of pedotransfer functions could be an applicable alternative way to predict the TV, particularly on large scales.