Quantitative evaluating the effects of land use conversion on soil quality of southern Mashhad area

Land use type is one of the most important factors affecting the soil quality. In this study for evaluating the effects of land use change on soil quality, 18 soil properties (TDS) were determined as soil quality indicators in 60 soil samples of agriculture and range lands with 1800 ha area in southern Mashhad (Iran). Also, pore size distribution curve for 40 soil samples was determined as another indicator of soil quality. The quantitative values of soil quality were calculated by six models (IQITDS, IQIMDS, NQITDS, NQIMDS, CR, and SI) for studied samples. The results showed that changing of land use from range land to agriculture decreased significantly the mean values of soil porosity, water stable aggregate (WSA), the slop of soil moisture curve at inflection point (Sgi index), mean weight diameter of aggregates (MWD) at P<0.01, and soil erodibility factor and plant available water content (PAWC) at P<0.05 and also caused the soil pore size distribution to be out of optimum range. Changing the land use by negative effect on soil physical properties degraded the soil quality. Also, it was shown the significant and positive correlation of macro aggregates (greater than 4 mm) with soil organic carbon percentage and Sgi index at P<0.01. Between studied models three models including IQITDS, NQITDS and SI were more sensitive to the land use change and had a significant difference in two land uses (P<0.01).