Investigating the Sustainability Situation of Agricultural Soils in Karaj Plain

Physical, chemical, and biological characteristics of soils are considered for studying soil quality, which has high importance for evaluating the degradation or improvement of lands. The soil quality of 140 samples in Karaj plain (Iran) was evaluated by using cumulative rating (CR) and Sustainability Index (SI) approaches. Some soil attributes such as, organic carbon percent (OC), mean weight diameter of aggregates (MWD), the slope of retention curve at inflection point (Sgi index), plant available water content (AWC), aeration porosity (Fa), acidity (pH), electrical conductivity (ECe), and sodium absorption ratio (SAR) of saturated paste extraction, soil texture, relatively field capacity (RFC), and bulk density (Bd) were measured for all 140 soil samples. SI for each sample was determined according to Sgi index, Fa, Bd, MWD, AWC, and OC. Relative weighing factor (RFC) was calculated for all attributes to determine CR. Then, sustainability situation of each sample was determined based on summation of RFC values. The results of SI approach showed that 62.14 % of the studied soils had unsustainable quality for use as agricultural land. In the studied soils, only 2.14 % had sustainable situation based on CR approach, 37.86 % will be sustained if more inputs or proper management are applied (such as returning the plant residues, reducing the tillage operatons, and modern irrigation methods) and 60 % were unsustainable for agricultural purposes. Thus, it seems that special management practices are necessary for the studied regions, which are located in arid and semi- arid area.