IDENTIFICATION OF SOIL QUALITY FACTORS AND INDICATORS FOR THE LOESS PLATEAU OF CHINA.

Soil quality has been significantly degraded in the Loess Plateau of China by soil erosion. Our objectives were to (i) identify regional-scale soil quality factors (groupings), (ii) select soil attributes within these factors that can be used as indicators of soil quality, and (iii) determine the impact of land use on these soil quality factors and indicators for the Loess Plateau in China. Soil samples were taken from the 0- to 20-cm depth in five catchments with 10 different land use types, and 32 soil properties were determined. Through principal component and discriminant analyses, the five critical soil quality factors identified were organic matter, texture, phosphorus, porosity, and microstructure. Within these factors, the individual attributes that best served as indicators of soil quality were organic matter, hydraulic conductivity, antiscourability, cation exchange capacity, invertase, mean weight diameter of aggregate, available phosphorous, and mean weight diameter of microaggregates. Among these indicators, available phosphorus, antiscourability, hydraulic conductivity, organic matter, and urease were highly sensitive to land use. Organic matter, hydraulic conductivity, and antiscourability were found to be the most important indicators to characterize soil quality in this loess plateau.