Establishing a Suitable Soil Quality Index for Semi-arid Rangeland Ecosystems in Northwest of Iran

Establishing soil quality index (SQI) is a common procedure in assessing soil capacity function. Various SQIs can be designed and used in soil evaluations upon the aspects including data set, efficiency, and sensitivity. This study was conducted to distinguish a representative soil minimum dataset (MDS) among 16 total dataset (TDS) properties in semi-arid rangeland ecosystems of northwest Iran. Appropriate SQIs were calculated applying the models of integrated quality index (IQI) and Nemoro quality index (NQI). IQI by simple additive and weighted additive approaches and also NQI were calculated for both MDS and TDS based on linear transformation of soil parameters. Totally, different SQIs including simple additive IQI, weighted additive IQI, and NQI were separately established to TDS and MDS. Sensitivity index (SI) and efficiency ratio (ER) of each SQI were then calculated for prioritizing and selecting suitable index. Principal component analysis (PCA) revealed that seven indicators are appropriate MDS for accounting 70.27% of data variations. Maximum and minimum SI belonged to MDS-NQI and TDS-weighted additive IQI, with values of 2.597 and 2.056, respectively. MDS-NQI has the highest value of ER (85.71), while TDS (both weighted and simple additive)-IQI has received the lowest value of ER (71.43). Final prioritizing according to ranks of SI and ER showed that MDS-NQI is the most suitable approach in soil quality assessment of semi-arid rangelands. Therefore, it could reduce cost due to measuring fewer indicators in the laboratory on contrary premise to have more dense soil samples in the field.