How to Measure Cover Crop Success

Evaluating the benefits of cover crops can be more complex than growing the crop itself.

We asked Rob Myers, Ph.D., for ways farmers can determine the effectiveness of cover crops. Myers is the regional director of extension programs for North Central Sustainable Agriculture Research and Education and director of the Center for Regenerative Agriculture at the University of Missouri.

Evaluate Soil Health

Cover crops improve soil health by adding organic matter, increasing soil fertility and improving soil structure. Farmers can measure soil health by exploring various soil parameters such as soil organic matter, pH, nutrient content and aggregate soil structure. Each parameter plays a crucial role in overall soil health.

“Cover crops do impact soil organic matter, but it takes time. It’s not something you will see immediately. It may take three to five years before you can detect that difference from a soil health measurement,” said Myers. “A faster way to evaluate the benefit of cover crops to soil health is through microbial biomass in the soil, and that could positively change in a single year, but cover cropping is a long-term project to receive the most soil health benefits.”

Determine Weed Suppression

Weed suppression is a key benefit of cover crops. Cover crops compete with weeds for light, water and nutrients. Farmers can analyze the success of weed suppression by scouting weeds in fields where cover crops were applied and fields where they weren’t. By comparing these fields, farmers can determine if cover crops are reducing weed populations, which could lead to fewer herbicide applications.

“Weed suppression is something you can see pretty quickly with cover crops. Some farmers say they can reduce their herbicide costs because the cover crop has helped reshape their weed management program. Rather than spraying post-emergence twice, they may only need one treatment,” said Myers.

Assess Erosion Control

Cover crops also reduce erosion by holding soil in place and improving soil structure. There are tools such as sediment traps or erosion pins that help farmers to assess erosion on their fields. However, a quick assessment can be made by driving around farmers’ fields during heavy rainfall events and observing the runoff from the fields.

Evaluate Nutrients

Some cover crops, such as winter peas, are capable of fixing nitrogen that can be used by the soybean crop later in the season. Farmers are encouraged to use soil sampling. Soil sampling gives farmers a clear picture of what nutrients crops will need in the future. Over time, hopefully a farmer can reduce the amount of fertilizer inputs due to the incorporation of cover crops. Note that cover crops are known to slowly release nutrients back into the soil as the plant tissue breaks down, so initial soil tests might not tell the whole story.