A Multivariate Assessment of Management Practices and Soil Quality in Illinois.

The long-term implementation of crop rotation and tillage influence the soil environment through inputs and disturbance of the soil, which in turn, impact soil quality. The first step in evaluating soil quality is to identify soil parameters that are sensitive to changes in the soil and indicative of the functioning occurring within the soil. Soil samples from 0-10 and 10-20 cm depths were collected from two Illinois experiments evaluating the effect of crop rotation and tillage, which were established 17 years previously. Crop rotation and tillage were evaluated with separate principal component analyses (PCA) of 20 soil parameters. Six principal components accounted for 74% of the variability among rotations. The soil parameters loaded within these components highlighted the strong influence on carbon and nitrogen cycling indicated by greater soil organic carbon, total nitrogen, microbial biomass, and aggregate stability under crop rotations with greater biomass production. The use of nitrogenous fertilizers in grass species influences several aspects of the soil, including soil pH, which in turn, affects the availability of essential crop nutrients, such as Fe and Zn. The PCA for tillage explained 73% of the variability with six principal components; of those, three were able to separate no-till from the conventional tillage. As with rotation, the choice of tillage practice can have a large influence on the cycling of carbon and nitrogen, as decomposition of residues and soil organic matter are accelerated by conventional tillage compared to no-till. The use of no-till was also related to soil stratification of pH and many nutrients that was not found under conventional tillage. For crop rotation and tillage, soil parameters related to carbon and nitrogen cycling as well as those affected by the application of nitrogen fertilizers have the greater potential for use in comparing the soil quality under different agronomic practices.