“We let the cover crop get as tall as it can,” says Adam Chappell, a no-till corn, cotton, rice, and soybean farmer at Cotton Plant, Ark. “We’ve learned that the bigger the cover crop gets, the more biomass we get, and the more diverse the cover crop the bigger the benefits.”
He plants his commercial crops into the green cover, then kills the cover with herbicides before the crops emerge. But, he says he understands why some growers might be reticent about the practice.
“I’ve heard growers say that if the cover crop gets that big, you can’t plant into it,” he said at a Cover Crops Conference held by the Arkansas Soil Health Alliance. “But, you can plant into it — you don’t need anything special. The equipment we use is probably the same type of planter you have.”
Chappell says he learned much of what he knows about cover crops by watching YouTube videos done by cover crop enthusiasts in other parts of the country. Here are some tips for growing cover crops that he and other proponents have developed for the Mid-South:
- Cover crop diversity
Plant cover crop mixes. Adding a legume to the mix can increase the soil nitrogen level by 80 pounds to 160 pounds, Chappell says. “We’re learning that we can reduce our nitrogen applications by about 30 percent for corn behind a cover crop mixture.”
Cover crop mixtures can be more expensive. Chappell and other members of the ASHA say they spend from $30 to $35 per acre for cover crop seed and planting. “But, the benefits are greater than the costs because of added soil nutrients and improvements in soil health,” says Lonoke, Ark., farmer Robby Bevis, who is president of the ASHA. “Some of these cover crop species can put roots 7 feet to 8 feet in the ground, which helps break up the soil.”
If you don’t feel comfortable planting multiple species, start simple with crops like wheat or cereal rye. Once you have a season or two under your belt, you can add more diversity.
- Drill cover crops
Drill cover crops when possible. Because of time constraints, some farmers broadcast cover crops into the summer crop or old crop residue, but cover crop specialists advise against it.
“The broadcast method of seeding is successful about half the time,” says Greg Brann, soil health specialist with the Tennessee Association of Conservation Districts. “We would prefer that people drill it. I know it takes more time, but that’s the best way.”
For example, specialists say if growers decide to broadcast, they should try to time seeding of cover crops when soybean leaves are beginning to turn yellow and rain is forecast within a day or two of planting.
- Use a decision aid to help plan your cover crop program
Use a decision aid to help plan your cover crop program. Land grant universities and the USDA Natural Resources Conservation Service have developed software programs that can provide checklists for making sure you account for costs before you commit to the approach.
One is the Cover Crops Cost Calculator (https://bit.ly/2Mgohlz), developed by Naveen Adusumilli with the Department of Agricultural Economics and Agribusiness at the LSU AgCenter. USDA has a NRCS Cover Crop and Tillage Decision Tool (https://bit.ly/2vvy7Xe) to help growers determine costs and benefits, and to learn if NRCS cost-share assistance is available.
- Plan for crop termination
Plan for cover crop termination. Whether you decide to follow university recommendations and kill the winter vegetation three to four weeks before planting in order to eliminate a “green bridge” for insects, or you wait until planting, you need to have a plan.
Most land-grant universities advise terminating cover crops or winter vegetation ahead of planting, so cutworms, pea leaf weevils, southern corn rootworms, three-cornered alfalfa hoppers, slugs, and other pests cannot simply move to the commercial crop. Killing the covers at that time may also help with planting for those new to cover crops.
“Some people say they can’t kill the cover crops when they get big,” says Chappell. “But you can, in a multitude of ways. Roundup works pretty well, as does Gramoxone.”
- Seed treatment for burndown
If you decide to terminate at planting, use a seed treatment such as imidacloprid.
“Where we did our burndown the day of planting, having a seed treatment mattered a lot,” says Dr. Scott Stewart, professor in the University of Tennessee Department of Entomology and Plant Pathology. “Without it, we basically lost the majority of our stand.”
He says insects such as pea leaf weevils, southern corn rootworms, three-cornered alfalfa hoppers and slugs will feed on soybeans and cotton when those crops emerge in newly killed cover crops. Finding slugs can be a challenge because they remain in the soil or under residue until late in the day or at night.
- Adjust herbicide program
You may be able to adjust your herbicide program. “We’ve seen great improvements in weed suppression, and in this era of weed resistance, we’re seeing some additions for the management of these weeds with cover crops,” says Dr. Forbes Walker, associate professor in the University of Tennessee Department of Biosystems Engineering and Soil Science.
In Arkansas, Chappell and Bevis say they have been able to save $75 to $80 an acre just by cutting out tillage practices associated with conventional weed control. They’re also using fewer chemicals in season.
“We’re growing some soybeans with just a pre-emergence herbicide application,” says Chappell. “And if we do have to come back postemergence, it’s usually with just one.”
- Furrow irrigation
Don’t give up on furrow irrigation. “Farmers look at the dense residue in our middles and when it’s time to irrigate, they say: ‘How do you deal with that?’” says Chappell. “We use a small furrow runner implement built by my brother, Seth, that creates a 4-inch trench, and we send water down that trench. We don’t need as much irrigation because the residue helps hold the moisture in the soil. But we can water.”
- Adding livestock
Consider adding livestock to your rotation. Mike Taylor and his son, Michael Taylor, Jr., who farm at Helena, Ark., have been grazing cattle on their cover crops to get more return on their investment. They’ve reported significant weight gains on the cattle while they’ve continued to improve their soils.
- Yield benefits
Don’t expect yield increases every year from planting cover crops. “We’re not growing cover crops just to get a yield benefit,” says Forbes Walker, who spoke at the Milan, Tenn., No-Till Field Day. “Don’t expect to get one every year. We are seeing a benefit when things go bad — when we have a dry year or a drought.”