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Long-term cover crop experiment: How much difference do cover crops make?

Principal Investigator

Laura L. Van Eerd

Research Institution

University of Guelph

External Funding Partners

Dr. Van Eerd’s two long-term trials at University of Guelph Ridgetown Campus have been funded by the Ontario Processing Vegetable Growers (OPVG) and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).

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

Project Start

April 2017

Project End

March 2022


  • Quantify the effect of long-term cover crop use on crop productivity and nitrogen (N) dynamics.
  • Evaluate the impact of long-term multi-species cover crop on crop productivity and N dynamics.
  • Compare crop yield variability over multiple years with and without cover crops as related to weather.
  • Quantify total carbon (C) inputs based on planting date over multiple years, to provide Ontario cover crop data for modellers of carbon sequestration.


  • Knowing the long-term impact (positive or negative) of cover crops on crop yield and yield stability over the years may assist growers’ management decisions when choosing cover crop practices that maintain crop productivity and competitiveness.
  • The generation of carbon inputs and carbon sequestration data based on long-term cover cropping may allow modellers to accurately predict how cover crops may impact carbon and nitrogen cycling under various environmental change scenarios.

Scientific Summary

While many research questions can be addressed with short term projects, there is a need to evaluate the impact of long-term cover cropping. Knowing the long-term impact (positive or negative) of cover crops on the following crop yield and resiliency over the years may assist growers’ management decisions when choosing cover crop practices that maintain crop yield, enhance ecosystem services and drive competitiveness.

Cover crops may play an important role in maintaining soil health and influence on carbon and nitrogen stores. But these soil changes can only be detected over the long-term. Ridgetown Campus has two unique state-of-the-art long-term cover crop trials focused on comparing multiple cover crops in Ontario and are likely the longest established trials in Canada and the Midwest USA. Dr. Van Eerd’s long-term cover crop trials were established in 2007 and 2008 and were designed to compare 4 different cover crops with a no cover crop control. The objectives of the trials are to determine the long-term impact of cover cropping on crop yields and resiliency based on known differences in soil health, which were quantified in 2015 and 2016. The main crop plots will be evaluated each year for yield, quality, above ground biomass weight, and carbon (C) and nitrogen (N) content. The cover crop plots each year will be evaluated for above ground biomass weight and C and N content in the fall and following spring. Finally, soil mineral N will be quantified by taking soil samples at main crop planting, harvest and in late fall (November). The project deliverables are to develop cover crop-specific best management practices (BMPs) that identify cover crop species and mixtures that increase crop yield and resiliency. In 2018, the first trial will be modified to evaluate different cover crop species mixtures that winter-kill or overwinter for their effect on growth and following corn crop yield.