Evaluation of soil quality under conservation tillage via factor and cluster analyses

In this study, factor (FA) and cluster (CA) analyses were used to evaluate the effect of the patterns of conservation tillage on soil quality. The squared Euclidean distance method of hierarchical cluster analysis was used for the cluster analysis. Twelve quantitative indicators related to soil property were selected based on results from long-term experimentation. Using factor analysis, five soil common quality factors (i.e., maintenance and supply capacity of soil nutrient, organic matter, phosphorus, bulk density, and enzyme activity) were derived from 12 soil chemical, physical and biological attributes. Factor scores show significant differences in superiority of the five common factors under different tillage patterns. Soil quality scores for conservation tillage (CT) are higher compared with traditional tillage (TT), implying improved soil physical, chemical and biological properties along with soil quality under CT. The top three integrated patterns with the highest scores include 30 cm subsoiling at one-year interval (NS2); combined straw mulching and 20 cm subsoiling, rotary tillage (SR2); and 30 cm subsoiling at yearly interval (NS3). This suggests outstanding advantage of the top integrated patterns in improving soil structure, soil fertility and overall soil quality. CA shows small differences in soil quality among different patterns under one tillage practice, indicating that tillage measurement is the key factor of soil quality.