CropLife Corn Effect

Growing Continuous Corn:
Residue Management Key To Yields

By Daniel Davidson, DTN Agronomist

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 CORN EFFECT exclusive three-part series, DTN Agronomist Daniel Davidson looks at how these growers have overcome the challenge of continuous corn to make it a profitable endeavor.

With a huge demand for corn to make ethanol and a run-up in futures prices, more growers are going to be planting corn in 2007. Most of those extra acres will be planted in fields that were in corn last year as well.

For many years, Extension specialists and university agronomists have been telling us to expect a yield drag of 10% to 20% in the first year of corn after corn. They point to research coming from small plots where corn following soybeans is compared to corn following corn.

I have looked at enough of these studies over the years to believe what they report, and I will not dispute their science. Though the science in these studies is sound, they don't necessarily represent the methods continuous corn growers are successfully using today. This winter I spoke to a number of farmers across the Corn Belt who are growing corn after corn. They told me their continuous corn yields are comparable and, in some cases, better than yields of corn grown in rotation.

Their conclusions are anecdotal and not statistically tested, but after I talked to enough of them and learned what they are doing, I began to see patterns in their practices and began to trust their observations and take confidence in their testimonials.

Growing continuous corn, even only for two or three years in a row, presents the same challenge: getting the corn planted so that it emerges quickly, evenly, and at the desired population. Meeting that challenge requires growers to rethink their tillage tools, the number and type of tillage passes, and how their planter is configured.

The largest problem growers face is the fact that corn produces more than twice the residue of a soybean crop. 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.

The number of growers I spoke to -- who have been growing continuous corn for several years -- all said the primary challenge is managing residue in order to create a seed environment similar to the one after a soybean crop.

The first step is choosing the best plot of land for continuous corn planting. One grower from north-central Illinois recommended selecting the best fields with the flattest ground and the darkest dirt to plant continuous corn. He plants his best land to continuous corn, while his more rolling upland fields that can be prone to drought are rotated between corn and soybeans.

Steve Butzen, agronomy information manager at Pioneer Hi-Bred, agrees and recommends growers choose fields that have a history of high corn yields, good drainage, and medium-textured soils with ample water-holding capacity.

The next step is handling the residue from the previous year's corn crop. Successful continuous corn growers will unanimously say corn residue has to be aggressively handled in the fall, starting with harvest. Corn heads should have knife rollers, and stalks should be cut down to eight to 10 inches tall.

After harvest, growers need to bury the residue. For some growers this means using a moldboard plow to turn the residue under; for others, it means shredding and ripping, double disking, or using a disk ripper to cut and bury the residue.

If growers do not plow in the fall, their spring tillage operation will become more important to establishing an environment that is conducive to quick and even seed germination. Spring tillage includes a pass with a field cultivator or soil finisher.

When it comes time to start planting, growers need to make sure soil conditions are dry enough to prevent sidewall compaction of the seed furrow. The cool, wet soils beneath the corn residue may mean that growers plant later than they would in corn-soybean rotation.

Watch soil conditions and the weather forecast more closely to select planting dates that improve your chances for success. Don't plant corn-after-corn fields too early when soils are below 50 degrees Fahrenheit and warmer weather is not in the forecast, said Pioneer's Butzen. Don't rush to get into wet fields. Surface compaction, sidewall compaction and/or deep compaction can restrict root growth and limit water update and yield, especially if drought conditions develop after planting.

All that to say plant when conditions are right, and remember that planting continuous corn is different than planting corn after beans.

In next week's Corn Effect, we will look at how to manage for disease and insect infestations as well as hybrids and fertility.
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Copyright 2007 DTN. All rights reserved.

Reprinted by permission of DTN

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

He can be reached at
daniel.davidson@dtn.com