Select your cover crop based on your soil health objectives.
Although they complicate management, cover crops can increase diversity and improve soil health in various ways
When you can spot a new practice from the highway, without even looking for it, it’s about to go mainstream. The latest example is cover crops.
Dan Towery, conservation consultant with Ag Conservation Solutions of West Lafayette, Ind., and Farm Journal Field Agronomist Ken Ferrie agree that cover crops offer significant soil health benefits. But just like any other practice, you need to do some homework, start small and then expand as you become more confident.
"A variety of crops in a rotation increases microbial diversity and helps manage insects and nematodes," Ferrie says. "Growing a legume cover ahead of corn can reduce the requirement for nitrogen fertilizer.
"Cover crops such as radishes can improve bulk density, which reduces surface hardness," Ferrie continues. "Covers can improve soil structure, which improves aggregate stability, which improves water percolation through the soil and water and oxygen levels within the soil."
Select your cover crop based on your soil health objectives. For example, legumes such as clovers and Austrian peas can provide mineralizable nitrogen for a corn crop. Forage radishes, like these pictured, can help break up compaction and improve soil structure.
What to expect. It might take many years to make big changes in soil health, especially if soil has been abused, Ferrie says.
"We have 2,000 acres in a corn, soybean, cereal rye rotation," explains farmer Steve Berger from Wellman, Iowa, who has no-tilled for 35 years and used rye as a cover for 10 years. "While it’s been challenging, especially to grow corn after the rye cover, we have seen organic matter creeping up, and we’ve had significant rains where we’ve avoided erosion."
In some situations, you might see signs of improvement fairly soon. In a one-year study, Ferrie saw how a rye cover crop improved carbon content, surface hardness, bulk density and water infiltration.
However, Ferrie has seen few situations where a cover crop actually provided a short-term financial return. "Perhaps we’ll find examples with future research," he says. "But it’s worth doing for stewardship and to increase the productivity of land for your heirs." Soil will improve some every year you grow a cover crop, Towery says. But how soon you’ll see measurable yield improvement depends on field history and what limiting factors, such as weather, are present in a given year.
Getting started. If you want to plant cover crops, Ferrie recommends starting with a soil physical. The procedure measures aspects such as soil texture, aggregate stability, available water capacity, surface and subsurface hardness, infiltration rate, mineralizable nitrogen and microbial activity.
"Finding problem areas in your soils will tell you which cover crops to plant," Ferrie says. "For example, if your soil is in pretty good health with good aggregate stability and waterholding capacity but short on mineralizable nitrogen, consider legumes such as clovers or Austrian peas.
The learning curve can be steep. Consult neighbors and other local sources to find out what covers are being grown successfully in your area and how to manage them. Online cover crop selection tools, such as the one published by the Midwest Cover Crops Council (www.mccc.msu.edu), can be helpful, too.
"When farmers ask me for advice, my first question is to ask them where they are from," Berger says, "because using cover crops is very geography and environment dependent." If you farm rented land, keep the landowner informed as you make your plans. Explain what you’re doing, and make sure he or she is supportive. Call on your local Natural Resources Conservation Service staff and ask whether you qualify for cover crop cost-share incentive programs.
Your first cover crop. "Start on a few acres," Ferrie says. "Expect problems, and don’t be discouraged—learn from them and make changes."
- December 2013