Combination cone penetration resistance/water content instrumentation to evaluate cone penetration–water content relationships in tillage research

Cone penetration resistance (PR) is generally regarded as one of the best tools to assess soil strength. However, effects of soil water content (WC) on measured PR can mask or confound interpretations of treatment effects on soil strength. Correction of PR data to common water contents, via empirical PR versus WC relationships, could help reduce such problems. This study used a portable combination PR/WC instrument to evaluate and formalize growing season (multiple year) changes in cultivation zone PR versus WC relationships for different tillage (conventional and no-till), trafficked, and corn ( Zea mays L.) cropping systems on clay loam soils in eastern Ontario, Canada. The results indicated expected negative linear and piecewise linear relationships between PR and WC for no-till soils. There was generally greater potential for higher PR at a specified water content for preferentially trafficked no-till soils, relative to no-till not receiving such a treatment. For tilled soils, negative linear relationships between bulk PR and WC were not as strong. Significant interactions between PR, WC, and days after planting (DAP), however, were uncovered using multivariate adaptive regression spline analyses. For non-preferentially trafficked tilled plots, linear negative relationships between PR and WC changed over the growing season and achieved strength/stability at approximately 90 days after planting; roughly 50 days after bulk density after planting effectively stabilized. For preferentially trafficked tilled plots, there were similar PR versus WC relationships, however, there were stronger interacting positive relationships between PR and DAP. The results from this work are promising for elucidating soil structural evolution over growing seasons for different tillage, trafficked and corn cropping systems on clay loam soils.