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Corn+Soybean Digest

Mastering Continuous Corn

John Agee is hard pressed when asked his secrets of continuous corn production. “What you do is really no different (than a corn-soybean rotation),you just have to watch over everything more closely,” he says.

Agee is perched in his black pickup to share his views while two combines lap around one of Agee Farms' numerous corn fields. Since the late 1990s, the operation has grown from about 2,500 acres to a dramatically larger scale, which Agee declines to pinpoint. The home base is in New Holland, IL, with farms scattered across seven counties in central Illinois.

“We never had a big plan to grow so big, it all just sort of snowballed,” says John, who farms with his son Justin and brother Jeff. They have help from eight full- and part-time employees, including several of the Agees' extended family members.

The Agee family planted 100% of their 2007 acres in corn, with about 85% of it corn-corn. They say their entire crop will likely be devoted to corn again in 2008. “The demand is so great right now we can't see doing anything differently at this time,” says John.

Growing corn year after year on the same ground comes with some performance risks. Researchers say corn growers can expect yields about 9% lower on the average for second-year corn vs. corn grown in rotation.

According to Purdue Extension corn specialist Bob Nielsen, much of the potential yield loss stems from heavy crop residue. Pound for pound, corn stalks and cobs left behind in a field equal the grain harvested. Heavy residue is difficult to navigate with planters and fertilizer applicators and it can interfere with springtime warming and drying of soils, potentially leading to slow germination, emergence and stand development.

Nielsen says growers also need to be aware of the impact high residue levels can have in carryover of diseases like gray leaf spot. In addition, heavy residues reduce the efficacy of soil-applied herbicides, and they can slowly modify soil environments to cause shifts in weed patterns.

“Growers who do a good job in managing residues are the ones facing less risk of yield losses in corn-on-corn,” Nielsen says.

The Purdue researchers warn growers to also be on the lookout for nitrogen (N) deficiencies in soil where corn is grown over multiple years. Some experts suggest growers need to add 30-50 lbs. more N per acre on corn-corn land versus corn grown with legume rotations. Farmers must also monitor other soil nutrients, especially potassium, which is important for maintaining strong healthy stalks.

The Agees are n't too worried about possible yield losses. As an example, Justin gestures to a field he recently combined that was half bean stubble and half corn residue when it was planted last spring. “Yield was almost exactly the same,” he states.

Here are five corn-corn tips from the Agee operation:

  1. Select the right hybrids

    The Agees test their soils extensively to evaluate soil conditions in each field. They also rely on yield monitoring and yield grid mapping to guide seed selection results. “That helps a lot in selecting which varieties to use on which soil types,” says Justin.

    When it comes to selecting seed suppliers, the Agees seek out companies that provide more than just products. “Basically, everyone has the traits,” says John. “We want the personal touch and to be able to trust that guy coming out and telling us which seed should go on which soil type.”

    John says, “You've got to have allies. The first thing you realize when you grow is that you can't do it all. You need a big talent pool and everybody has their part.”

  2. Manage residue

    The Agees have been strip-tilling for about 15 years and say it works well for corn-corn as long as they take a few steps to manage residue. First, they set the corn head and knife rolls to size residue stalks to less than 12 in. “Tall stringy stalks make problems for the planters and ammonia bars,” says John.

    The Agees also run an AerWay aerator over corn residue unless deep compaction is present (see below). “It pokes 6-in. holes in the soil and helps speed up the bacterial process of rotting the stalk,” says John, adding that another advantage is the aerator leaves surface soil largely undisturbed. “It churns up only a minimum amount of soil,” he says. “We feel aeration is very important in a strip-tilling situation.”

    Nielsen says that temperature and moisture are the two biggest factors in breaking down residue and believes this year's early harvest may have provided some advantages in residue management, especially for growers who strip-till or till shortly after harvest. “That may help start the decay while we still have some warm soil temperatures,” he says.

  3. Don't skimp on fertilizer

    Even before the aerator hits the fields, the Agees spread dry fertilizer containing potash and phosphate as soon after harvest as possible at levels based on each field's soil test and yield. After aeration is completed, the fields are ready for strip tilling.

    The Agees create an 8-10-in. ammonia strip with Blu-Jet ammonia tool bars with knives and sealers. Disk blades are angled to accommodate the soil type and amount of residue present. “You have to make sure the sealer is set just right to throw a nice mound,” John says. Otherwise, it can lead to poor planting conditions, he adds.

    Accuracy at planting time maximizes use of the ammonia strips. “The planter has to be matched up right on top of that groove,”says John. In the past, the Agees relied on field markers and their own or employees' tractor driving abilities to assure planter rows and ammonia strips were lined up. Two years ago they purchased John Deere auto-steer.

    “You can do it without automatic steer but this makes it much easier,” Justin says.

  4. Combat compaction

    The Agees keep a close eye on soil conditions during fall fieldwork to spot deep compaction problems that could limit root growth. “If we have a field where we think there is a compaction problem, then we run a para-tiller type chisel plow through it after harvest,” says John.

  5. Scout, scout, scout

    John and Justin scout heavily, with some help from their seed reps and other crop specialists, from early spring when they assess which fields are ready to plant through late fall when they are on the lookout for winter annual weed infestations. They aim to scout each field once a week.

“We scout for everything that can happen in a field including weeds, insects and disease,” says John. This past summer the Agees found gray leaf spot in several fields, prompting them to aerially treat their entire crop with a fungicide.

In the fall, the Agees look for winter annuals, such as common chickweed and henbit, and treat the most heavily infested fields first. “We'll apply to that 30% and then spray other fields as weather permits,” says John.

The Agees haven't found a single magic bullet to ensure success with corn year after year. “It takes it all — the right hybrids, the right amount of fertilizer and good scouting — to make it work,” says Justin.

Editor's Note: For more on continuous corn management, see http://cornandsoybeandigestcom/cornoncorn/cid=microsites and

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