Cover crops reduce nitrate leaching

40-year rotation trials find diverse rotation makes for more resilient crops

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Research findings released recently from the Soil Health Monitoring Station at Elora, Ont. suggest including cover crops in a rotation could significantly reduce nitrate leaching.

Using soil lysimeters installed at the Soil Health Monitoring Stage in 2016, researchers are exploring how crop rotations impact soil emissions. The lysimeters are large steel drums installed in ground wells containing a variety of sensors at differing depths that monitor soil health and collect the resulting data for research.

“We use the data collected to start answering questions about how rotations and cover crops impact soil health and crop productivity,” says Gordon Bell, graduate student at the University of Guelph. “Specifically, we’re looking at crop diversity, soil texture and climate change.”

In this particular study, researchers collected one year of lysimeter data comparing a simple crop rotation of soy and corn to a diverse crop rotation including wheat and cover crops along with soy and corn.

“Growing cover crops reduced the amount of nitrate found in the soil across the entire period of study,” says Bell. “The cumulative data shows that cover crops reduced nitrate leaching by 70 to 77 per cent. Without cover crops that nitrate would just drain down into groundwater and be inaccessible to crops.”

The results of this study are consistent with those of a long-term rotation experiment done on the same site over the past 40 years.

“We compared diverse crop rotations that include winter cereals and cover crops to a straight corn-soybean rotation, and we found that corn and soybeans yielded better in the diverse crop rotation,” says Cameron Ogilvie, knowledge mobilization coordinator for Soils at Guelph.

These results were amplified in extreme conditions. “In hot and dry years, corn and soybeans actually yielded 30 per cent better in the diverse rotation than in the simplified rotation,” Ogilvie says.

Soils at Guelph is a knowledge and innovation hub developed to help ensure Ontario soils are managed sustainably based on science-backed decisions.

“We summarize and share research results, and host and partner in events promoting knowledge sharing among researchers, farmers, crop advisors and industry,” says Ogilvie.

The health of the agriculture industry and, in fact, the entire population, depends on the ability to sustain healthy soil in which to grow food. “Soil is the foundation of agriculture, of food, feed, fuel and fibre. If we don’t have soil, we don’t have all of the benefits that come from soil,” Ogilvie concludes.

The research findings reported here, along with more information about soil research in Ontario, were shared during Canada’s Digital Farm Show Sept. 15 to 18. Video footage of the researchers sharing their results virtually can be found at

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