Corn on corn

FARGO, N.D. - No one seems to be counting how much corn-on-corn production there is in the region, but the general consensus is that it's on the rise as farmers work to meet the needs of an expanding corn-ethanol industry.

In North Dakota, an informal Agweek survey of seed company officials, crop consultants and farmers seemed to agree 5 percent is planted corn on corn in 2007, with perhaps 20 percent to 25 percent in some of the traditional corn areas of southeast North Dakota regions.

Matt Olson, a crop consultant for Centrol of Twin Valley, based in the Valley City, N.D., area, says he has some clients who have grown corn on corn consecutively on some fields for 20 years or more. Tom Richman of Maple Valley Ag in Tower City, N.D., says some farmers in his area are experimenting with using corn on corn to rehabilitate high-salt areas in fields where soybeans are no longer a good option.

At the universities, no one is recommending farmers go to more corn on corn, per se, but more information is being gathered, to help farmers go into the practice with wide-open eyes.

Mike Catangui, extension entomologist and associate professor at South Dakota State University in Brookings, recently offered corn-on-corn research trial talk on the subject at a field day at SDSU's Northeast Farm at South Shore north of Watertown.

"It's not very common in South Dakota, but it's very common in Nebraska," Catangui says, of the corn-on-corn practice. Catangui did doctorate studies at the University of Nebraska-Lincoln before coming back to SDSU in 1993.

"I knew people (in Nebraska) who have now been in continuous corn for 50 years," Catangui says. "We have an Estellline, S.D., producer who's been in corn for 40 straight years. Those cases are exceptions (here) because we have a lot of crops to rotate with."

Joel Ransom, a North Dakota State University extension cereal crop agronomist in Fargo, thinks corn-on-corn rotations are not as common a choice as soybean-on-soybean rotations. He doesn't expect a huge shift toward this, as farmers in the north have to think about residue management.

Ransom says that while farmers are economic incentives, farmers also have to deal with the consequences. There can be a "yield penalty," at least in the first few years of growing corn, at about 6 percent to 9 percent per year.

Catangui says those aren't true in every field. There is a nitrogen "credit" with soybeans in the mix, but corn after corn typically requires up to an extra 40 pounds of nitrogen per acre, compared with corn after soybeans, Ransom says.

Diseases traditionally haven't been a problem in corn on corn in this area, Ransom says.

He says some of the corn yield contest winners actually are promoting corn on corn, he says, noting that the yield penalty eventually may decline.

"There are those smaller downsides that are issues of profitability," Ransom says. "I think there's always a worry about continuous monocultures. A lot of surprises occur that are not happy surprises."

Catangui is a bit more bullish on the practice.

The SDSU extension entomologist since 1997, Catangui says insect challenges are one of the big issues involving corn-on-corn feasibility.

"It's one of the major reasons we rotate corn with soybeans," he says.

While corn on corn can be done, the universities need to help find out what happens when the practice becomes more widespread, which he thinks it will.

Corn prices have declined, recently, but the prospect of $3- to $4-per-bushel corn has changed a lot about how farmers have thought about their cropping patterns, and more of them are thinking about corn on corn, he says. The advent of so-called Bt corn traits and Roundup Ready have made corn on corn much easier.

Insect challenges

The original Bt corn works against corn borers, but since 2003, another generation of Bt characteristics has worked against corn rootworm larvae, which of course operate underground.

"It's our job in the university to scan the horizon and predict will happen if they keep growing corn on corn, to be ahead of the trend and see what will become important," Catangui says. "We need to get ready with (treatment) thresholds, so farmers have treatment options five or 10 years from now, on some emerging insects."

Catangui has continued some corn insect studies that had been started by his predecessor, Murdick McLeod. Initially, Catangui was focused on corn borer, but now he's looking below ground. He estimates that 20 percent of his job now is involved with corn issues.

"We are doing an inventory of every single insect from the roots to the ears," Catangui says, about an ongoing study. "We're looking for bugs in the roots, including the rootworm - anything at all that's associated with the roots."

Catangui says it wasn't initially easy to acquire the needed corn-on-corn area within the university's research farms.

He's been able to do corn on small plots continuously for six years at the university's Beresford station and for two years in Brookings and South Shore. The studies generally look at a range of treatments, with conventional and Bt corn, and compare liquid and granular insecticide treatments. The study is designed to compare yield results and economic returns.

Among the pests of interest underground:

Corn rootworm. Chewing and burrowing on the roots causes visible lodging, but also disrupts the flow of nutrients and water from the roots to the rest of the plant. Bt corn has been a big boon here, he says. The standard thinking is that crop rotation works, but newer studies are starting to indicate rootworms are a problem even where rotations put as many two other crops between corn crops. Catangui has come up with low-tech ways of using plastic cups to count bugs in the roots, instead of the standard way of putting a cage over the soil and counting what emerges from it. Some studies simply rate the damage, while Catangui counts the insects.

Corn root aphid. As with all aphids, the damage from this pest comes from sucking the juices from the corn root. Catangui says this insect always has been in the "background" but traditionally isn't a problem. He thinks it could become a bigger problem. When Catangui started looking for aphids six years ago, he'd only find a root aphid in about one out in 100 roots.

"It was a novelty," he says. "Now, we're finding it in every single plant in Brookings, and more in Beresford."

A graduate student is looking at whether the incidence is somehow related to particular corn hybrids, but it's too soon to say more about that. The aphid has an interesting life cycle: The aphid lays eggs on the soil surface and they are "collected" by cornfield ants in the fall and taken into the ant nests underground.

"Then those ants will distribute the eggs of the aphids on the roots when the corn is available in the spring and summer," he says. The aphids are literally "farmed," like ants do with other aphids. The ants feed on the "honeydew" or digested sugar from the aphids.

Others. Wireworms and white grubs both chew and prune the roots. Again, the granular insecticides that were used before the Bt traits had suppressed the pests. Corn root nematodes also damage roots and interfere with absorption.

Above ground, he's looking at:

European corn borer. Attacking the stalks, leaves and ears, this threat has been largely neutralized by Bt corn, although it still is an issue in the so-called "refuge" acres.

Western bean cutworm. Feeds on the ears and kernels. This native insect traditionally is a pest of dry edible beans. Catangui saw the insect when he was working in western Nebraska. Recently, he's started to seeing the insect in corn in high numbers the southeast part of the state in 2000, and has been increasing northward. He theorizes that because the most common Bt corn doesn't target them, the other insecticides farmers have stopped using may have been suppressing them. The corn with the Herculex I gene works against several insects, including the bean cutworms.

Sap beetles (picnic beetles). Feed on the kernels.

Rootworm adults. Feed on the silk and developing kernels and "clip" silks, disrupting pollination. It isn't susceptible to the Bt characteristics.

Corn leaf aphid. Feeds on the husk of the corn ears and sucks the juice.

"It also prevents pollination if there's a lot of them - same with the rootworm adult beetles," he says.

Many pests that attack the ears can make the plants susceptible to fungi development, which can lead to mycotoxins such as aflatoxin.

Corn-on-corn solutions may be important for corn ethanol, but there will be other issues if the corn-fuel ethanol industry shifts toward corn stover cellulose to ethanol-based industry.

David Clay, an SDSU soil scientist, is the principal investigator in a multiyear study designed to define sustainable site-specific production guidelines for corn stover harvesting. The work is being done in South Dakota, but should be applicable to surrounding states such as Minnesota and North Dakota, Clay says.

The project is being funded to the tune of $250,000 a year by the South Dakota Corn Utilization Council, which is interested in how much corn stover can safely be removed for cellulosic material. The Natural Resources Conservation Service recently kicked in $500,000 per year for similar work, which will run for five years.

One part of the project will determine the role of things such as switchgrass and prairie cork grass to protect areas of fields where the stover harvest is not feasible. The researchers intend to use DNA analysis to indicate the affects of crop sensitivity to stover removal.