SENECA FALLS, NY – Cover crops are multitaskers, helping maintain healthy soil through a variety of means. Matt Ryan, associate professor at Cornell’s School of Integrative Plant Science Soil & Crop Sciences Section, presented “Cover Crops for Sustainable Agriculture” as part of a New York Soil Health Field Day recently, hosted by Rodman Lott & Son Farms.
“Cover crops can help us in soil health,” Ryan said. “There’s increased interest in soil health, which is driving the interest in covers.”
He listed the key steps to soil health: Limit soil disturbance; keep the soil covered; have live roots growing throughout the year; and use crop diversity to increase soil diversity. Cover crops help with each of these areas.
Soil health also depends upon the effects of chemicals, such as pH, nutrients, toxins and salts; physical effects, like tilth, structure, aeration and drainage; and biological effects, including beneficials, pests and roots.
“Since 2012, cover crop adoption has increased 50%,” Ryan noted.
In 2012, 10.3 million acres of farmland nationwide used cover crops. By 2017, that number increased to 15.4 million acres. Although this is good news to Ryan, he said that firstname.lastname@example.org only 5.1% of harvested cropland, excluding alfalfa.
The top states using cover crops in 2017 were Maryland (32.6%), Delaware (20.4%), Connecticut (19.5%), Pennsylvania (16.9%) and Virginia (16.2%). New York ranks 16th, with 9.2% of harvested cropland utilizing cover crops.
Farmers have numerous reasons to use covers, such as reducing soil erosion; enhancing mycorrhizal numbers; adding nitrogen (when using legumes); suppressing weeds; suppressing nematodes; increasing water infiltration; decreasing soil compaction; attracting beneficial insects; decreasing nutrient loss; increasing soil aggregation; and adding organic matter.
As for weed management, cover crops help by reducing competition for resources, allelopathy, altered microenvironment, physical suppression, herbivores and pathogens and management through mowing.
“When using herbicides, cover crops can help manage herbicide-resistant weeds,” Ryan said.
He views cereal rye as an all-star cover. It’s the most winter hardy and can be conveniently seeded right after corn grain harvest. It also offers biological nitrogen fixation. “It’s one of the best covers crops we have,” Ryan said.
Effective cover cropping requires planning not just for this season but for times far beyond. For example, red clover can be frost seeded into winter wheat, providing nitrogen for the subsequent corn crop. It’s often used in a corn/soybean/wheat rotation.
“It’s an easy way to get a legume cover crop into that rotation,” Ryan said.
Selecting a cover crop depends on the issue you want to address. “It’s important to think about the goals you’re going after,” Ryan said.
Annual rye grass is an example of grass that prevents erosion. Want to reduce soil compaction? Consider a brassica, such as forage radish.
Environmental constraints also affect cover selection, as does the time of year, the biology of the cover crop, the planting method, establishment and termination, soil and field conditions, cropping system and rotation and seed cost and availability.
“The Northeast Cover Crop Council and Extension agents can help,” Ryan said. The NCCC offers recommendations.
Farmers should look at the impact a cover crop may have on the crop yield as well as the return on investment for the cost of growing and terminating the cover. In fact, in some cases, the short-term ROI may not appear to pay off. But Ryan prefers looking at the long-term investment also.
“You’re increasing resiliency to extreme weather events,” he said.
His research shows that farmers report higher yields with covers than without. Farmers don’t have to wait long. The biggest jump is between the first and second years.
In a survey by the American Seed Trade Association, 67% of farmers agree or strongly agree that cover crops can reduce yield variability during extreme weather events.
Ryan was involved in a project between 2019 and 2020 that studied planting green with no-till management and optimal nutrition application. The cover crops were mechanically terminated with a roller/crimper that planted in the same pass to reduce labor. Among the participants, 70% reported improved weed control; 68% saw better soil moisture conditions; 17% experienced improved slug management; and 27% were able to manage disease better.
Planting green worked better for soybeans than corn, which experienced population loss. Planting green in corn also requires estimation of nitrogen credits and debits and a higher risk of early season pests.
“Weed diversity was significantly reduced in year one, but not year two,” Ryan said. “Sometimes, we don’t get what we expect, and results vary by year. We didn’t see any difference in corn stalk rot. We didn’t see a significant difference in yield. We are seeing a bit of yield drag.”
Corn yield increased with application of nitrogen fertilizer along with cover crop treatments.
“Cover crops can increase sustainability, but more work is needed to determine the best management,” Ryan said. “There are opportunities to no-till plant organic crops into rolled/crimped cover crops.”