Cover crops help mitigate climate change

What do you need to know?

Climate change is one of the most important environmental challenges we are facing, and its negative impacts are becoming more and more visible. Soil is known to store at least three times as much carbon than our atmosphere and four times as much as the rest of life on Earth. Therefore, identifying and adopting land management practices through which we can increase the capacity of soil to store carbon will be a crucial climate change mitigation strategy. 

Planting cover crops is an effective strategy to increase the capacity of agricultural soils to store carbon. Cover crops are crops grown for benefits other than being harvested for profit. This study confirmed that the amount of carbon stored in soil was between 11 – 22 % greater with cover crops than without cover crops. In terms of yield benefits, this study found that not all main crops grown in the rotation after cover crops resulted in higher yields than without cover crop. Despite the benefits from cover crops in carbon sequestration and potentially mitigating climate change, cover crops adoption by farmers is likely to remain low without financial compensation.

Why is this research important?

Storing atmospheric CO₂ in soil is an important strategy to mitigate climate change. It is important to understand and identify which agricultural practices will increase the soils capacity to store carbon. Cover crops have various benefits for agricultural systems, such as reducing nitrogen leaching and improving overall soil quality. Additionally, over time planting cover crops can increase the amount of carbon stored within soils and might help to offset greenhouse gas emissions. The mechanism through which cover crops enhance soil carbon storage is not well understood but might be due to a reduction in loss of carbon from soil or protection of carbon within the soil aggregates.

However, cover crops come with a variety of associated costs and additional demands for management. For farmers to be willing to plant cover crops, it needs not only to be profitable for long-term soil health, but also be profitable economically.

What did the researchers do?

A long-term cover crop experiment was established in 2007 and the experiment was repeated in 2008 in a nearby location. Both experimental plots are located at the Ridgetown Campus, University of Guelph in Southwestern Ontario. They evaluated four different cover crops and a control (without cover crops) in a crop rotation consisting of grain and processing vegetable crops.

To understand the impact of cover crops on carbon storage and on main crop yield, the following measurements were taken:

• Carbon content within the aboveground biomass of each cover crop and main crop analyzed each year
• The main crops were harvested and yield quantified
• Soil samples were taken in 2015 and 2016 to identify the amount of organic carbon stored in the surface soil (0 to 15 cm depth)

In addition to the biological measurements, they also did an economic analysis where they compared the profit made from the main crop harvest with the economic costs of planting each type of cover crop. Costs associated with planting cover crops range from costs for seeds to herbicide application.

Both sites had four replications where cover crop treatments (no cover crop control, oat, radish, cereal rye, and a mixture of cereal rye and radish) were applied in plots of 6m x 16m.

The main crops grown in the crop rotation were:

• Grain crops (Spring wheat, Winter wheat, Grain corn, Soybean)
• Vegetable crops (Sweet corn, Tomatoes (grown twice) & Squash)

What did the researchers find?

After compiling all the data from this long-term cover crop trial, these were the most important results:

• The main crop grown influences the amount of cover crop growth and thus the carbon content.
• Soil organic carbon content with cover crops was 11-22 % greater than the control treatment
• Reduced yield variability with cover crops present
• Greater profit margins when using cover crops over the 8 years of the study and when evaluating only the vegetable crops
• Loss in profit margins for grain crops that can be overcome by financially compensating farmers for carbon stored

About the researchers

Dr. Inderjot Chahal is a post-doctoral researcher and Dr. Laura Van Eerd is a Professor at the School of Environmental Sciences. Dr. Richard Vyn is an Associate Professor and Danielle Mayers was an MSc student at the Department of Food, Agriculture, and Resource Economics. All authors are working at the University of Guelph, Ridgetown Campus, Ridgetown, Ontario, Canada.

The Ridgetown Campus is one of 15 agricultural research stations across the province that are owned by the Agricultural Research Institute of Ontario and managed by the University of Guelph through the Ontario Agri-Food Innovation Alliance, a collaboration between the Government of Ontario and the University of Guelph.

Keywords

Cover crops, service crops, climate change, mitigation, agriculture, profit margins, soil carbon sequestration, yield, vegetable crops, grain, oilseed crops, carbon trading

Citation

Chahal, I., Vyn, R. J., Mayers, D., & Van Eerd, L. L. (2020). Cumulative impact of cover crops on soil carbon sequestration and profitability in a temperate humid climate. Scientific Reports, 10(1), 1-11. https://doi.org/10.1038/s41598-020-70224-6