Top 10 Tips for Managing Continuous Corn

Tom Fink is no stranger to growing corn on corn. His father raised continuous corn on the family’s northwest Illinois farm for decades. The 1988 drought pushed Fink to a corn-soybean rotation, and he returned to continuous corn after 2006 to capture more profit potential. “We grow really good corn in Carroll County,” says Fink, who farms near Chadwick, Illinois. His average yields over the past two years have ranged from 215 to 245 bushels per acre. “It comes down to management,” he says.

Continuous corn can be unforgiving. “About 15 years ago, nearly two-thirds of the growers around here had at least 75% of their acres in continuous corn,” says Blake Miller, a Syngenta agronomic service representative (ASR) in Illinois. “Many got burned by agronomic failures after three or four years.”

“When I’ve had a question about a specific Syngenta product, I’ve been able to talk to the scientist responsible for it. The Syngenta team wants to stay connected to the farmers they serve.”

Making continuous corn work means knowing what you’re up against. “We have to go into continuous corn with a higher management level than we would with other cropping systems,” says Mark Licht, Ph.D., an assistant professor and cropping systems specialist with Iowa State University Extension.

Pay Attention to Agronomy 101

Getting the basics right is essential, notes Kevin Scholl, a Syngenta ASR who farms in Illinois. “You don’t want to let your corn have a bad day. Everything you do should help reduce plant stress.”

Reducing plant stress includes:

1. Location. Fields selected for continuous corn should have good drainage, high water-holding capacity, good fertility, no compaction problems, and low insect and disease pressure.

2. Residue management. Healthy, high-yielding corn can produce increased residue levels that can hinder emergence, seedling establishment and yield potential of the next crop. Typically, yield drag is between 5% and 15%, although it can reach 30% in some cases, Licht notes.

   “Residue can also create a large source of inoculum that can contribute to increased disease pressure,” says Andy Heggenstaller, head of agronomy at Syngenta Seeds.

   Appropriate residue management starts at harvest. Fink uses a stalk-chopping head on his combine. So does Matt Kellogg, who raises continuous corn near Yorkville, Illinois. “The particle size of the residue is closer to the size of a postage stamp, so it breaks down faster,” says Kellogg, who also uses a chisel plow in the fall to help manage residue.

3. Soil fertility. Use soil tests to determine whether you need to add lime and/or additional phosphorus and potassium. “Be sure to fertilize to at least maintenance levels,” says Randy Kool, a Syngenta ASR in Iowa. Additional nitrogen, he notes, is often required as well for maximum yield potential.

4. Hybrid selection. Choose hybrids designed for high-residue situations. Also, consider hybrids’ emergence scores, stress-tolerance ratings, seedling vigor and root/stalk scores. Invest in a strong, defensive disease package, since prior-year residue can harbor disease pathogens, including northern corn leaf blight, gray leaf spot, Goss’s wilt and Diplodia stalk rot. “The Syngenta Seeds portfolio includes hybrids that are particularly well-adapted to continuous corn,” Heggenstaller says.

5. Planting conditions and seeding rates. A slight seeding rate increase of 5% to 10% may offset stand establishment challenges that can occur in fields planted to continuous corn. “We’re fairly aggressive with our seeding rates, which are in the upper 30,000 seeds-per-acre range,” Kellogg says.

   Recommended seeding rates also depend on the tillage system involved. “With strip-till or conventional tillage, you typically don’t need to increase the seeding rate, but you may want to consider it with no-till,” says T.J. Bins, a Syngenta ASR near Leoti, Kansas.

6. Stand establishment. Seed placement is critical for uniform spacing and emergence, and that requires proper residue management. In the spring, Kellogg uses a disk finisher to get the seedbed as level as possible. “You need good seed-to-soil contact for proper stand establishment,” Scholl says.

7. Disease management. While seed treatments protect seedlings from root and shoot infections, foliar fungicides help protect the plant during the grain-fill period. “Our area had a lot of issues with tar spot in 2018,” Scholl says. “Growers had good results by applying a fungicide with their post-emerge herbicide application.”

   Kellogg relies on Trivapro^® fungicide. “It did a good job of controlling tar spot and northern corn leaf blight,” he says. With three active ingredients (Solatenol^® fungicide, azoxystrobin and propiconazole), Trivapro can be applied between the V4 and V8 growth stages for longer-lasting control of tar spot, gray leaf spot, northern corn leaf blight and other diseases.

   “Then at VT to R1, you may want to do an aerial application of Miravis^® Neo fungicide,” Miller says, referring to the Syngenta fungicide that provides broad-spectrum disease control in corn and soybeans.

8. Insect control. Weekly scouting for insect pressure is critical to success with continuous corn, Fink says. Protect against corn rootworms and European corn borers by using traits that help control above- and below-ground insects.

   Growers concerned with corn rootworm should have a multiyear corn rootworm management plan in place for each field that includes multiple control strategies, including crop rotation, corn-rootworm-traited corn hybrids, soil-applied insecticides and adult beetle management.

   “When I was scouting fields, areas with the highest pressure from corn rootworms were almost always in continuous corn,” Licht says. “Also, these growers were using the same trait year after year. It’s important to diversify the insect traits you use.”

   By offering both Agrisure Duracade^® and Agrisure^® 3122, Syngenta is the only provider offering trait stack choice with differing dual-mode, corn-rootworm-control protein combinations.

   Kellogg prefers the Agrisure Duracade trait, which contains a unique mode of action to help control corn rootworm. He also uses Force^® Evo liquid corn insecticide. “Using a combination of Agrisure Duracade and Force Evo helps us control the bugs,” he says.

   Another option is Force^® 6.5G insecticide, a high-load granular formulation that gives you proven corn rootworm control with fewer stops to refill, Scholl says.

9. Weed management. Controlling weeds is vital to maximize yield potential in continuous corn. “You’ve got to keep your fields clean,” Fink says. “I use Acuron^® herbicide upfront.”

   With four active ingredients, Acuron controls the tough weeds other products miss. Acuron can be followed with Halex^® GT herbicide to deliver post-emergent weed control, with residual that lasts until crop canopy in glyphosate-tolerant corn. “Layering in preemerge herbicide and residual herbicides goes a long way toward controlling weeds until the crop canopy takes over,” Scholl says.

10. Controlling volunteer corn. Like any other competing plant or weed, volunteer corn can reduce yield in continuous cornfields by robbing the crop of available light, nutrients and water. Even though they could potentially help offset these losses by contributing to yield, volunteer plants just don’t have the ability to produce the amount of grain that hybrid corn does, Scholl says.

    Because volunteer corn is selective to corn herbicides, controlling it in continuous corn is difficult. The best management strategy is to reduce stalk lodging, kernel losses and ear droppage that lead to volunteer corn, Kool says. Growers can also adjust their fall tillage strategy to help mitigate volunteer corn the next year. By allowing seed to stay on the soil surface in the fall, growers may be able to reduce populations the following season so that germination takes place prior to freezing temperatures, which will kill the emerging volunteer plants.

Working with Syngenta has helped Kellogg get excellent results with continuous corn. “It’s easy to get the answers you need,” he says. “When I’ve had a question about a specific Syngenta product, I’ve been able to talk to the scientist responsible for it. The Syngenta team wants to stay connected to the farmers they serve.”