Assessment of Surface Sealing Formation and Its Relationship with Soil Quality Indices

Surface sealing is a special phenomenon in most arid and semi-arid regions with severe agricultural and environmental consequences that reduces the porosity of soil surface and infiltration, and increases runoff and soil erosion. The aim of this study was to evaluate formation of surface sealing and its effect on soil quality indices. In this study, 40 soil samples (0-10 cm) were collected from different land uses from eight provinces of Iran. The most important physical and chemical properties of the soil samples were measured. Also, surface sealing index (SI), and saturated hydraulic conductivity (Ks) and air permeability coefficient (Ka) were evaluated before and after rainfall application. The results showed with the exception of four forest soil samples with mean organic carbon of 5.5% and SI>1, all soil samples were prone to seal formation. Also, due to seal formation, both Ks and Ka were reduced in average by 58%, and in terms of soil quality, the scores of these two indicators were reduced by 57% and 66%, respectively. Evaluation of soil quality by integrated and Nemero quality indices showed that the soil quality score is overestimated for most of the soils when SI and its effect on Ks and Ka were not accounted in evaluation. This overestimation was less than 5% for the soil samples with stable aggregates, and more than 20% for the soils with weak aggregates.