Investigating Soil Quality in Part of Kuhin Lands in Qazvin Province, Iran

Soil quality can be studied from two aspects: intrinsic soil quality and dynamic soil quality. The intrinsic aspect of soil quality is influenced by soil-forming factors, but the dynamic aspect of soil quality includes the characteristics of soil that change depending on the type of management and indicate the state of soil health. In this research, soil quality of a part of Qazvin lands, in Iran, was calculated using two cumulative soil quality indices and Nemro quality index. The results showed that the cumulative quality index was consistent with the spherical model and the numerical quality index was consistent with the exponential model, and the coefficient of determination of both indices was 0.87, which indicates a good correlation between the fitted model and observation points. Compared to the Inverse Distance Weighting (IDW) method, for both soil quality indicators, the normal kriging method had a lower value of the mean skewness error and root mean squared error (RMSE). Soil quality maps of the studied area were drawn with the help of two indices of cumulative quality and numerical quality based on the conventional kriging method. The pattern of soil quality was almost the same for both indicators. Based on the cumulative quality index, the soil in the northern and northwestern parts of the study area had the lowest soil quality values (0.4 and 0.3) while the southern and southeastern parts had the highest values (0.7 and 0.5), respectively. Two soil quality indices showed a positive and significant relationship with organic carbon, cation exchange capacity, nitrogen and potassium, but these relationships with bulk density and soil acidity had a negative and significant relationship. It can be concluded that the soil quality of the region is affected by the dynamic characteristics of the soil and it is important to pay attention to maintaining these characteristics.