How can you build soil organic matter? How long does it take and what’s the impact on yield?
University of Guelph researcher Laura Van Eerd and Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) soil management specialist Anne Verhallen tackle these questions in this 2021 Ontario Diagnostic Days video report. The researchers visit Van Eerd’s long-term cover crop trials at Ridgetown College to explore what this research is telling us, including cover crops’ impact on yield, organic matter and soil resiliency.
Verhallen has some tough questions for Van Eerd, beginning with whether cover crops can build organic matter in Ontario farm fields.
“Yes, definitely, it works,” says Van Eerd as she points to research she’s conducted at Ridgetown where organic matter levels in the sandy loam soils have increased from 3.4 to 3.9 percent with long-term cover crops including cereal rye and radish — a 15 percent increase. She notes that the cover crops help accumulate organic matter in two ways: by protecting the soil from wind and water erosion and carbon inputs — capturing sunlight and converting carbon dioxide to plant material. (Story continues after the video.)
There’s growing North American evidence of the impact of cover crops. Van Eerd says an ever-growing number of long-term trials that require 10 years of cover cropping are showing organic matter increases ranging from 10 to 42 percent.
Van Eerd also explores the impact cover crops and the resulting organic matter can have on crop yields. She points to 2020 side-by-side trials where corn planted in long-term cover crop soil out-yielded corn planted in non-cover crop soil by 59 bu/ac. She attributes these yield gains to the resiliency cover crops and organic matter contributed to the soil, as well as the more efficient nitrogen cycling in the dry, stressful 202o growing environment.
But growers who want these soil and yield benefits need to be in it for the long haul. Van Eerd notes that a growing body of research indicates it takes about 10 years of cover crops to make an impact. “The bottom line is it takes time. It takes patience and commitment. It’s not one and done.”
Click here to view the entire 2021 Ontario Diagnostic Days series.