Hybrids, Fertility, Treatments All Factor Into Success

Growing continuous corn comes with its share of risks, but many growers across the Corn Belt have learned how to make the practice work on their operation. In this exclusive three-part series for CORN EFFECT, DTN Agronomist Daniel Davidson looks at how these growers have overcome the challenge of continuous corn to make it a profitable endeavor.

The amount of crop residue left behind after corn harvest is roughly equal to the weight of the grain harvested; for example, a 100-bushel-per-acre corn crop leaves behind around 5,600 pounds of crop residue per acre.

The heavy residue left behind can cause cooler, wetter soil conditions, and this can result in planter sidewall compaction, delayed corn germination and emergence, delayed seedling growth rate, and increased exposure to soil-borne diseases and insects prior to full-stand establishment.

“Corn rootworm is the number one corn insect pest associated with corn-after-corn production,” says Steve Butzen, agronomy information manager at Pioneer Hi-Bred International. “Effective control measures are critical for this pest, as corn rootworm pressure tends to be highest in the second and third years of continuous corn. For control, choose hybrids with a transgenic trait or an insecticide seed treatment or apply a granular soil insecticide.”

To reduce the risk of secondary insect damage, corn borer pressure and corn rootworm feeding, growers should use a soil-applied insecticide (Poncho or Cruiser), Bacillus thuringiensis (Bt) insect protection traits or treated seed. All of the farmers I interviewed this winter have fully embraced double- and triple-stacked corn. They believe that Bt protection against corn borer and corn rootworm along with seed treatment insecticides are very important to their success.

Continuous corn under minimum or no-till systems leaves a lot of residue on the surface that serves as a food source for a number of corn pathogens including seedling blight, stalk rots, and leaf diseases. Burying residue so it decays rapidly helps minimize this problem Aggressive fall tillage practices that cut and bury the residue can help reduce levels of inoculum, but even so, resistant hybrids should be selected with knowledge of what specific diseases need to be controlled.

Selecting hybrids that perform under the challenging field conditions in continuous corn is a key management decision. Every continuous corn grower I spoke to agreed that selecting hybrids was important. They counted on their seed dealer to recommend hybrids, and though these growers didn’t endorse any hybrid in particular, they all said planting Bt corn with protection against corn borer and corn rootworm is a must.

Peter Thomison, corn Extension specialist at The Ohio State University, says growers should select hybrids that have demonstrated high-yield potential across diverse environments and stress conditions. “Only hybrids with above-average ratings for drought tolerance, stalk strength, and emergence under stress conditions such as low temperatures and cold, wet soils should be considered,” he states.

Hybrids with resistance to gray leaf spot, northern corn leaf blight, anthracnose and gibberella stalk rots, and diplodia ear rot are also attractive, he said.

But choosing the right hybrid is only half the battle. Growers need to pay close attention to soil fertility, especially nitrogen.

Soil fertility in continuous corn should be based on soil tests and local state fertility recommendations. Soil test levels (STL) should be in the medium to high range. The soil pH should be at 6.2 or above.

Many of the corn growers I talk to on a regular basis like using a starter fertilizer because of the bump it gives to early seedling growth. Starter fertilizer is especially beneficial on soils with low fertility and provides uniform seedling growth during extended cold periods in the spring. This is important when growing continuous corn in high residue situations.

Phosphorus (P) and potassium (K) requirements are similar for continuous corn compared to corn after soybeans, but corn removes more P and less K from the soil than soybeans. Since most growers probably anticipate increasing their corn acreage to a two-thirds corn and one-third soybean rotation, this fertility difference would have a negligible short-term effect in a continuous corn rotation.

But continuous corn will require more nitrogen than corn rotated after soybeans. All of the farmers I talked to this winter said they always applied an extra 40 to 50 pounds of nitrogen per acre to compensate. Many also put on nitrogen in two or three applications to increase the crop’s nitrogen-use efficiency while keeping the overall nitrogen rates low.

The cornstalks left on the field provide more organic matter to improve soil tilth and fertility. This same organic matter will mineralize and release nitrogen and other nutrients back to the soil for the next corn crop. Because of this natural recycling and release of P and K, fertility levels probably will not change, and after a field has been in continuous corn for five or more years, most long-term continuous corn farmers realize they no longer have to apply an extra dose of nitrogen because the soil readily provides it.

To summarize, disease outbreaks are a risk when planting continuous corn, but do not let it worry you too much. All the continuous corn farmers I spoke with said they never experienced any more of a disease epidemic in their continuous corn then in their rotated corn and were not worried about the impact. But they all practiced aggressive tillage that buried much of the residue, planted into an ideal seedbed, and used planted hybrids that were recommended for continuous corn. In other words, they used good management to negate the risk.

As illustrated, growing continuous corn requires different management strategies than those employed in a corn-soybean rotation; they’re not necessarily more difficult, just different.

Next time we will look the practical economics of planting continuous corn and a recap of all three articles.

SOURCE: Croplife and DTN

Editor’s note: This is the second installment of an exclusive three-part series written by Dan Davidson, DTN agronomist, based in Omaha, NE.

Click to read the first installment, Residue Management Key To Yields.