relationships between some soil quality indicators in different agricultural soils from varamin, iran

soil quality is a necessary indicator of land management. different indices are applied to evaluate farming systems, soil types and land uses based on soil quality. the slope of retention curve at its inflection point has been defined as soil physical quality index (si) but the relationships between si and penetration resistance (pr), the least limiting water range (llwr), and available water content (awc) have not been studied yet. in this study, i) the effects of soil physical properties on si index and pr, and ii) the relationships between si index and pr, llwr, and awc were investigated. seventy undisturbed soil samples were collected and the slope at inflection point for soil retention curve as a soil physical quality index (si) was determined in each sample using soil retention curve data. furthermore, pr was measured in soil surface, and llwr and awc were calculated. the results showed that the correlations between pr and water content, electrical conductivity (ece), sar, and si index were significant at p