Ten years of soil data suggests that regardless of soil texture, pH, or crop rotation, there’s one thing that impacts soil carbon more than anything else — temperature.

Dr. Ed Gregorich, soil research scientist with Agriculture and Agri-Food Canada (AAFC) based at Ottawa, Ont., is drawing on data from a long-term, national soil study. Gregorich says even he was surprised by the finding.

In high moisture areas, sandy soils, clay soils, low moisture, and even high pH soils, about 94% of the variability in carbon cycling in the soil was attributed to temperature. We already know that certain geographic regions can build soil organic matter more quickly than others — compare southern Ontario to central Saskatchewan, for example. But what this long-term study wanted to know was if it was moisture, temperature, texture or a combination of all three factors that drove crop residue breakdown, soil microbial processes, and, ultimately soil’s appetite for carbon.

Gregorich says as average temperatures climb, even in small increments, farmers are going to be increasingly challenged to conserve and build organic matter levels in soil, something that is already a significant challenge in warm, wet climates, such as Ontario.

Listen below as Gregorich explains what the AAFC study found and how this will inform and influence soil management and crop rotations in the decades to come: