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Interseeding cover crops options for grain corn and their effects on soil health in Southern Ontario

Principal Investigator

David Hooker & Mehdi Sharifi

Research Institution

University of Guelph / Trent University

External Funding Partners

This project was funded in part through Growing Forward 2 (GF2), a federal-provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario.

Project Start

April 2015

Project End

May 2018


  • Assess the most common cover crop species and their mixture for their establishment rate, biomass production, and competitiveness with grain corn in three major Southern Ontario corn growing regions.
  • Evaluate the effect of interseeding cover crops on a range of soil health parameters with short-term turn over, including soil pH, total soil organic carbon (C) and N, particulate organic matter C and N, readily mineralizable soil N, soil mineral N (NO3, NH4), microbial biomass C and N, soil enzyme activities (beta-glucosidase and dehydrogenase)


  • The adoption of interseeded cover crops has the potential to increase soil organic matter, which may lead to several benefits such as enhanced soil water holding capacity, water infiltration rate, improve soil health, and increase nutrient cycling.
  • The adoption of interseeded cover crops has the potential to improve long-term soil productivity, profitability and environmental sustainability for Ontario grain production.

Scientific Summary

Long-term crop rotation research in Ontario (University of Guelph) has shown that a corn-soybean rotation has lower productivity compared to more diverse rotations that include wheat, especially during growing seasons with a shortage or excessive rainfall. Lower productivity is associated with poor soil structure and lower soil organic carbon compared to more diverse rotations. The importance of building resilient soils and best cropping practices is evident, but convincing grain farmers to grow perennial crops or incorporate cover crops in crops other than wheat has been a challenge. One promising option for extending corn-based rotations benefits to ensure long-term profitability in cool temperate climate is to introduce interseeding cover crops in corn. Establishing a cover crop into corn has the potential to build resilience in short rotations with improvements in soil health. It is therefore important to investigate interseeding cover crop options, benefits, risks and uncertainties.

This project investigates soil and economic impacts of interseeding cover crops into corn harvested for both grain or silage corn. At three locations in Ontario (Ridgetown Campus, Elora Research Station, and Trent University experimental farm in Peterborough), corn intended to be harvested as grain or silage will be interseeded (InterSeeder Technologies Inc. from Penn State) with four cover crop treatments at the V5 developmental stage: 1) planted red clover, 2) planted annual ryegrass, 3) a planted 1:3.3 mixture of red clover and annual ryegrass, and 4) broadcast-only mix of red clover and annual ryegrass. Plots without interseeded cover crops will be included as controls for comparison, bringing the total number of plots at each site to 20. The experiment will be repeated for three seasons from 2015 to 2017, to give a total of 9 site-years. The final outcome of the project would be ranking of the interseeding cover crop treatments in terms of establishment, biomass production, competitiveness with grain corn, and effects on sensitive indicators of soil health and residual soil nitrate at harvest. The soil health and soil nitrate reduction benefits will be linked with long-term environmental sustainability. The risk and cost analysis of the practice in 3 sites over 3 years will provide a great tool for making decision by growers on adoption of the technology.

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