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Evergreen farming in southern Ontario: more effective use of cover crops in rotations involving corn, soybean, or winter wheat


Xueming Yang & Dan Reynolds


Harrow Research and Development Centre, Agriculture and Agri-Food Canada (AAFC)


April 2017


June 2021


  • The overall objective of this project is to develop recommendations for using cover crops in corn-soybean-winter wheat and corn-soybean rotations grown in medium and fine textured soils (e.g. Brookston clay loam) in the lower Great Lakes watershed. The specific project objectives include:
    • Determine seeding practices which optimize emergence of cover crops when seeded into winter wheat stubble after wheat harvest.
    • Determine the most suitable cover crops for seeding into early-stage corn.
    • Evaluate methods for cover crop termination in wheat stubble, cover crop incorporation, and cover crop effects on root zone nitrogen concentrations and corn yield.
    • Determine if there can be reductions in nitrogen fertilizer inputs for corn as a result of the cover crop “nitrogen credit”.
    • Determine the impacts of cover crops on soil organic carbon content and soil physical quality such as soil hardness, water storage and aeration.


  • The successful communication of how to effectively and efficiently integrate cover crops into field-crop rotations will assist farmers in improving their stewardship of the land by increasing nutrient use efficiency, and improving the soil’s resilience to water excesses (temporary flooding) or water deficits (droughts).
  • The successful incorporation of cover crops into field-crop rotations and maintaining year-round land cover may lead to measurable improvements in the water quality of the lower Great Lakes, which are critically important sources of water, fish and recreation for both Canada and the United States.


Soil and water quality in southwestern Ontario are important to maintain in order to achieve improvements in field-crop yields, reduce sediment in streams and lakes, and limit appearance of dead zones and algal blooms in the lower Great Lakes, especially Lakes St. Clair, Erie, and Ontario. Water quality is of national and international importance because the Great Lakes represents about 20% of the world’s fresh water reserve, which is shared and relied upon by more than 40 million Canadians and Americans for drinking water, field-crop irrigation, commercial and sport fishing, and general recreation. Agriculture has an acknowledged role in the soil and water quality of the Great Lakes watershed. Farmers recognize that intensive crop production systems can lead to the degradation of the soil by decreasing soil structure, permeability, and soil organic carbon content. Cover crops may play an important role in maintaining soil health and influence carbon and nitrogen stores. Although there are many anticipated agronomic, economic, and environmental benefits to using cover crops, they can be difficult to implement in crop rotations with long-season crops such as corn and soybean as there are not sufficient growing degree days left in the fall for successful establishment when the cover crop is planted after harvest. Preliminary work suggests that seeding certain cover crops (e.g. hairy vetch, red clover, crimson clover) after winter wheat harvest can significantly reduce losses of nitrogen from agricultural lands by: 1) scavenging “left-over” nutrient after harvest from the crop root zone and storing the nutrient; and 2) by increasing the soil’s ability to store air and water, sequester organic carbon, and retain and recycle nutrients within the crop root zone.

The anticipated outcome of this research project includes recommendations for better selection and management of cover crops to improve the economic and environmental performance of corn-soybean-winter wheat rotations in southwestern Ontario. This research project will address gaps in our knowledge regarding: i) which cover crops are best suited for planting into wheat stubble or standing corn (i.e. intercropping); ii) the best method for termination and incorporation of the cover crop; iii) which cover crops are most effective for scavenging “left-over” nutrient after harvest, increasing soil organic matter, and improving soil physical quality; and iv) how much “nitrogen credit” cover crops provide to corn on southwestern Ontario’s medium and fine textured soils (e.g. Brookston clay loam) in the lower Great Lakes watershed.

In Ontario Grain Farmer Magazine

“Interseeding Cover Crops”, March 2018 issue.

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