Evaluating cover crops for the long term

Too early to assess corn and wheat yields, but the benefits to tomatoes already seem clear

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It’s widely recognized that cover crops boost soil organic matter, but their long-term agronomic and economic benefits are less well understood. Researchers at the University of Guelph’s Ridgetown and Elora campuses have undertaken some long-term studies to identify the impacts of cover crops in some growing conditions and management styles common to southwestern Ontario.

Why it matters: There are many variables that influence how effectively cover crops contribute to the health and viability of a farm. Long-term studies at Ridgetown and Elora intend to help measure and quantify those variables.

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Ridgetown graduate student Matt Stewart and associate professor Dave Hooker are part of a research team investigating the long-term effects of cover crops on the productivity of corn, soybeans and wheat, as well as impacts on soil health and stress resilience.

The project comprises 527 field test plots divided between the two research stations. They include both corn-soybean and corn-soybean-wheat rotations, and incorporate everything from plots planted with no cover to those planted with mixtures of 10 species. All plots are divided between full-tillage, strip-till,and no-till plots with randomized nitrogen treatments on cover crops as well as additional nitrogen applications on corn.

“It’s pretty unique… we’re trying to emulate what farmers in the southwest might do,” says Stewart.

Now in the second year of its 20-year duration, he says it’s still early to draw many conclusions — this will be the first year where they can gather corn yield data.

However, differences in above-ground cover crop biomass were recorded between the first two years, as well as between the Ridgetown and Elora plots — the latter showing noticeably less biomass, which Stewart attributes to the region’s slightly cooler conditions.

“While I’m hoping to be done by May next year, the project should stay more or less the same,” says Stewart.

Includes vegetables

The long-term effects of cover crops in processing-vegetable crop rotations is better understood. Laura Van Eerd, associate professor in the School of Environmental Sciences at Ridgetown, has been part of a similar research initiative that began in 2007. This project looks at how single-species as well as four, eight, and 12 cover crop species blends affect soil health for grain and processing tomatoes.

Van Eerd says soils consistently planted with cover crops have shown improvements on several fronts.

“We’re a decade in and we’re seeing changes in soil organic matter,” she says. “We’re doing other soil health measurements… pretty much no matter how you measure it we can see improvements.”

Laura Van Eerd’s project looks at how single-species as well as four, eight, and 12 cover crop species blends affect soil health for grain and processing tomatoes.
photo: Matt McIntosh

One improvement is yield. Van Eerd says there was a significant correlation between soil health and processing tomato yields. During a demonstration day at Ridgetown College on October 23, Van Eerd said after planting 136 different cover crops to date, crop yield was only hurt once.

“It should be a no-brainer, but that we could achieve (yield increases) in a relatively short period of time; that should be the selling point. It’s not a lifetime,” she says.

Among future areas of focus, Van Eerd and her colleagues hope to investigate how cover crop systems and soil differences relate to processing tomato quality. Despite the “very forgiving” nature of the sandy loam that comprises most of her research plots, Van Eerd also wants to explore how things would differ on more degraded and different types of soil.

“We know from long-term tillage trials that winter wheat is very valuable… that’s where (Stewart’s) research is interesting,” says Van Eerd. “Maybe in a decade we will be able to see the synergy between adding winter wheat to the rotation, as well as cover crops.”

About the author


Matt McIntosh

Matt is a freelance writer based between Essex County and Chatham-Kent. He is interested in all things scientific, as well as rock n' roll, hunting and history. He also works with his parents on their sixth-generation family farm.



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