Long-Term Tillage and Crop Rotation on Soil Health at Four Locations in Ontario, Canada.

Tillage systems and crop rotations affect soil quality and thereby influence agricultural sustainability. However, quantifying and integrating the numerous soil quality attributes is complex. One method of measuring overall soil quality is the Cornell Soil Health Assessment (CSHA), developed for New York; however, its applicability for other regions should be evaluated. Soil samples were collected from the 0-15 cm depth in 2009 and 2010 at four long-term (14-29 years) experimental sites in Ontario (Ridgetown, Delhi, Elora, and Ottawa). The impact of long-term tillage systems (no-till vs. conventional tillage) and crop rotation (monocultures or rotations with grains, legumes, forages) was evaluated on up to 17 soil quality attributes and the applicability of the CSHA for use in Ontario assessed. The CSHA score was 6-14% higher with no-till vs. conventional tillage at all sites except Ottawa, which was not different. At Ridgetown and Elora, crop rotations which included winter wheat, alfalfa or small grains undersown with red clover tended to have higher CSHA scores, while lowest scores were with continuous corn or soybean-corn. At Delhi and Ottawa there were no differences in CSHA scores among crop rotations. By combining all the soil attributes in a principle component analysis, the first two factors accounted for 62% of the cumulative variability. The structure present along the first two factors was mainly determined by site, but no clear relationship between components for tillage system or crop rotation was observed.  Based on the principle component analysis, we identified five groups of closely related soil attributes; which may lead to possible refinement of a soil health test for Ontario using as a composite, weighted score of the five identified groups.  This study provides a framework for improving overall soil health testing and is the first study to evaluate soil quality among all four Ontario long-term experiments.