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

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

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

Healthy, productive soil is critical to enhancing the long-term profitability of agriculture. 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. Two unique and state-of-the-art long-term cover crop experiments have been run at the University of Guelph, Ridgetown Campus, for the past 10 years. Each year in the long-term cover crop experiment, above-ground primary productivity (biomass) and carbon inputs of all plants (cover crops and main crop) have been quantified.

The overall goal of project is continue the established long-term cover crop experiments to improve our understanding of the influence of long-term cover cropping on crop yield stability and resiliency by investigating carbon (C) and nitrogen (N) cycling. Trial #1 will be switched from a cover crop planting date trial to a multi-species cover crop trial, in a rotation of soybean, winter wheat followed by cover crops, grain corn, snap beans followed by cover crops and sweet corn followed by cover crops. The multi-species cover crops will be chosen based on type (mixes of grasses, legumes and broadleaves) and their management (i.e. winter kill versus overwinters and requires chemical or mechanical termination) and compared to a no cover crop control. Trial #2 continues to be a cover crop trial using oats, cereal rye, oilseed radish, a mix of oilseed radish and cereal rye, and no cover crop control with the main crops of peas, sweet corn, spring wheat, tomatoes, grain corn, squash, soybeans, and winter wheat, tomatoes, peas. Trial #2 will also be evaluating the impact of removing or retaining crop residues of grain corn and winter wheat. The main crop plots will be evaluated each year for yield, quality, above ground biomass weight, and carbon and nitrogen 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).

Grain Farmers of Ontario is the province’s largest commodity organization, representing Ontario’s 28,000 barley, corn, oat, soybean and wheat farmers. The crops they grow cover 6 million acres of farm land across the province, generate over $2.5 billion in farm gate receipts, result in over $9 billion in economic output and are responsible for over 40,000 jobs in the province.