JWSS - Journal of Water and Soil Science

Saturated hydraulic conductivity (K_s) is one of the most important soil physical characteristics that plays a major role in the soil hydrological behaviour. It is mainly affected by the soil structure characteristics. Aggregate size distribution is a measure of soil structure formation that can affect Ks. In this study, variations of K_s were investigated in various aggregate size distributions in an agricultural soil sample. Toward this aim, eight different aggregate size distributions with the same mean weight diameter (MWD= 4.9 mm) were provided using different percentages of aggregate fractions consisting of (< 2, 2-4, 4-8 and 8-11mm). The Ks values along with other physicochemical properties were determined in different aggregate size distributions. Based on the results, significant differences were found among the aggregate size distributions in K_s, particle size distribution, porosity, aggregate stability, electrical conductivity (EC), organic matter and calcium carbonate. The aggregate size distributions with a higher percentage of coarse aggregates (4-8 and 8-11 mm) also showed higher K_s as well as clay percentage. A positive correlation was also observed between Ks and clay, aggregate stability and EC, whereas sand showed a negative correlation with K_s. No significant correlations were found between K_s and silt, porosity and organic matter. Further, multiple linear regression analysis showed that clay and aggregate stability were the two soil properties controlling K_s in the aggregate size distributions (R²=0.80, p<0.01). Aggregate stability was recognized as the most important indicator for evaluating the K_s variations in various aggregate size distributions.

Wind erosion is known as one of the most important land degradation aspects, particularly in arid and semi-arid regions. Soil properties, by affecting soil erodibility, can control the wind erosion rate. The aim of this study was to attribute the soil physical and chemical properties to the wind erosion rate for the purpose of determining the most important property. To this aim, wind erosion rates were measured in-situ at 60 points of Kerman province using a portable wind tunnel facility. The results indicated that wind erosion rates varied from 0.03 g m^-2 min^-1 to 3.41 g m^-2 min^-1. Threshold wind velocity decreased wind erosion rate following a power function (R²=0.81, P<0.001). Clay and silt particles, shear strength, mean weight diameter (MWD), surface gravel, dry stable aggregates (DSA<0.25mm), soil organic carbon (SOC), calcium carbonate equivalent (CCE) and the concentrations of the soluble Ca²⁺, K⁺ and Mg²⁺ were inversely proportional to the wind erosion rates following nonlinear functions. On the other hand, Wind erosion was significantly enhanced with increasing the sand fraction, soluble Na⁺, electrical conductivity (EC) and sodium adsorption ratio (SAR). According to the final results, among the studied soil properties, SAR and MWD were s the most effective properties controlling wind erosion in the soils of Kerman province. Therefore, it is recommended to consider suitable conservation practices in order to prevent the sodification and degradation of arid soils.