[Comprehensive method for evaluating soil quality in cotton fields in Xinjiang, China].

. These values were all below the national standards. However, the Cu, Zn, and As concentrations were greater than the background values in Xinjiang, indicating the accumulation of those elements in the soils. When the Nemerow comprehensive pollution index (PN) of heavy metals was less than 0.5, the comprehensive soil quality improved as the soil physicochemical properties improved. Soil organic matter, total N, Cu, Zn, As and Pb were the main variables affecting soil quality in the main cotton cropping regions of Xinjiang. The cotton growing areas in Xinjiang generally had medium soil quality. Changji and Kuitun had the highest SQI (0.52) whereas Aksu had the lowest value (0.31). Soil quality was generally highest in northern Xinjiang, followed by western area, and then southern area.