Cover cropping today is anything but a one-size-fits-all approach or a fix-all fencerow prescription. During statewide Soil Health Sustainability for Cropland workshops, Natural Resource and Conservation Service experts taught producers to tailor soil health strategies to meet individual needs.
“If soil health is the goal, crop diversity cannot be ignored or overstated,” said Doug Peterson, NRCS soil health specialist for Missouri and Iowa. “Soil health is not just organic matter, infiltration, or any other one thing — so there really isn’t one cover crop species that will solve everything.”
Peterson said the first step to developing a personalized soil health strategy utilizing cover crops is to examine individual and property-specific goals by asking a few key questions:
•What are my goals for each field?
•What environmental considerations am I making?
•Is there a time frame?
•What’s the budget?
For a typical corn-soybean rotation, Peterson suggested cover crops like rye, oats or wheat in combination with nitrogen-fixing legumes like peas to increase nutrient recovery in the soil.
“Oats are one of the most mycorrhizal plants there are so the oats will really start giving that biology a jump start,” Peterson said. “The peas will fix a little nitrogen which will also help the system.”
Referred to as the workhorses of the corn-soybean rotation, Peterson’s cereal crop suggestion won’t come as a big surprise to no-till enthusiasts — his planting timeline, however, is more unconventional.
“In a corn-soybean system, a springtime planting before soybeans will be our biggest opportunity to have a cover crop grow,” Peterson said. “Generally our soybeans are planted a little later so we have a big opportunity.”
For a spring planting ahead of soybeans, Peterson recommended a mixture of oats and winter peas. For fall planting after wheat, he recommended a mixture of sorghum sudangrass, pearl millet and sunflower — emphasizing the importance of diversity of root structure beneath the soil and plant structure above the soil.
Above all, Peterson encouraged producers to consider a variety of options before subscribing to one cover crop mix. Because some herbicides have a half life as long as a full year, Peterson suggested planning cover crop strategies two years in advance to prevent any clash between herbicide protocols and cover crop varieties.
“What we are trying to do is to get as many roots spread as uniformly across that soil as possible because we are trying to affect all of the soil and not just a single row,” Peterson said.
Technology has provided a wide variety of strategies for dispensing cover crops — from manure-mixed slurries to using vertical tillage. With hundreds of application techniques, Peterson recommended starting out simple and allowing soil structure to dictate application methods.
“Early on, I will typically recommend drilling,” Peterson said. “Drills do a good job and get good seed-to-soil contact regardless of soil conditions.”
Estimating the cost of planting with an air seeder or no-till drill to be around $12-$16 per acre, Peterson suggested a different but similarly priced option for long-term no-till soils. Using a plane to fly seeds over a field is cost effective and gives random plant spacing for even field coverage but requires optimum soil conditions.
“Long-term no-till soil is very porous and aggregated at the surface so when they fly it on, there are lots of cracks and fissures for the seed to get into,” Peterson said. “That is opposed to long-term tilled soil that is slick, smooth and hard with few places for seed to go.”
Timing is also a critical element for cover crop seeding success, with crops providing continuous soil coverage in an ideal situation.
“When there is a little bit of yellowing in the soybeans — that’s the target you are looking for,” Peterson said. “You want to fly the cover crop on and have the soybean leaves drop on top of it to kind of mulch it.”
Companion and relay cropping are newer methods traditional cover cropping is quickly approaching, Peterson said. In companion cropping a cover crop is planted while a cash crop is still growing; in relay cropping, two cash crops are grown simultaneously.
Both systems increase the amount of time the soil is covered by a producing crop and give growers a head start on production.
“In this system, you’re shooting for a time frame when you still have enough sunlight to get the cover crop to grow but not so much that it shades it out and kills it early on,” Peterson said. “Then what you have to do is hope the cover crop survives the shady part of the year and is ready to explode once the corn is harvested.”
A typical companion cropping strategy is to plant a cover crop alongside corn while giving a side-dress nitrogen application, Peterson said. The process increases ground cover and root structure diversity without creating a lot of extra work during the growing season.
“I think companion cropping is really where we need to be headed, even this far south, to have our cover crops growing alongside our cash crops,” Peterson said.
Cover crops in any application have numerous benefits — both financially for producers and biologically for the soil. Peterson encouraged farmers to consider the health of their soil and finding a cover crop strategy that works for their needs and goals.
“We know we can build organic matter, improve nitrogen cycling and ground cover, increase beneficial insects and pollinator habitat — all through cover crops,” Peterson concluded.