Organic Carbon and Nitrogen Stock Indices and Mechanical Properties of Soils in Two Land Uses in Northeastern Iran

This study aimed to investigate the effect of land use type on some soil characteristics, including Carbon stock (CS), Nitrogen stock (NS), S-Index, Structural Stability Index (SSI), soil pore size distribution, soil shear strength (τ), internal friction angle (φ˚), shear Cohesion (C), Soil Water Characteristic Curve (SWCC), Relative Field Capacity (RFC), Available Water (AW), Aeration Porosity (AP), and effective Porosity (Pe) in Shandiz City, Khorasan Razavi Province, northeast Iran. For this purpose, ۶۰ soil samples were taken from the surface layer (۰-۲۰ cm) in pasture and agricultural land uses. The results showed that S-Index, SSI, RFC, AW, Pe, Cs, and Ns in the Pasture Land Use (PLU) were significantly higher than in agricultural land use. The values of τ, C, and φ˚ in the pasture land use were significantly (p<۰.۰۱) less than the agriculture land use. The relationship between soil organic carbon stock index and bulk density (r= -۰.۶۹), coarse fragments (r= -۰.۷۳), cohesion (r= -۰.۷۰), and φ˚ (r= -۰.۵۲) were significant and negative. The amounts of C and N stock indices in pasture land use were ۶۱.۶% and ۳۳.۱ % greater than agricultural lands, respectively. Therefore, as a result of land use change, C and N stock, S-index, RFC, SSI, AW, AP, Pe, and, consequently, the soil quality decrease, and soil degradation increase in agricultural land use.

کلیدواژه ها:

S - Index ، Carbon stock ، Shear Strength ، internal friction angle ، Relative field capacity ، land use