Abstract: Classical statistics methods were adopted to analyze the soil quality variability, its affecting factors, and affecting degree at a regional scale (700 km²) in the central part of hilly Loess Plateau region of China. There existed great differences in the variability of test soil quality indicators. Soil pH , structural coefficient, silt content, specific gravity, bulk density, total porosity, capillary porosity, and catalase activity were the indicators with weak variability; soil nutrients (N,P, and K) contents, CaCO₃ content, cation exchange capacity (CEC), clay content, micro-aggregate mean mass diameter, aggregate mean mass diameter, water-stable aggregates, respiration rate, microbial quotient, invertase and phosphatase activities, respiratory quotient, and microbial carbon and nitrogen showed medium variation; while soil labile organic carbon and phosphorus contents, erosion-resistance, permeability coefficient, and urease activity were the indicators with strong variability. The variability of soil CaCO₃, total P and K, CEC, texture, and specific gravity, etc. was correlated with topography and other environmental factors, while the variability of dynamic soil quality indicators, including soil organic matter content, nitrogen content, water-stable aggregates, permeability, microbial biomass carbon and nitrogen, enzyme activities, and respiration rate, was mainly correlated with land use type. Overall, land use pattern explained 97% of the variability of soil quality indicators in the region. It was suggested that in the evaluation of soil quality in hilly Loess Plateau region, land use type and environmental factors should be fully considered.

Key words: soil quality, variability, land use, environmental factor, hilly Loess Plateau