September was wetter than normal in much of Iowa, as rains came when corn and soybeans in many fields were reaching maturity and harvest 2018 was off to an early start. Even in southern Iowa where it was dry this summer, fields finally received rain in late August and into September — too much in some cases.

That’s not the best situation if you like to leave corn standing in the field to dry on the stalk instead of harvesting at a higher moisture content and paying for propane to run a grain dryer.

Iowa State University grain quality specialist Charlie Hurburgh began alerting farmers in early September of the need this fall to start harvesting corn early and at a higher grain moisture than they intended. The idea is to avoid problems with mold developing on ears in the field, especially fields with downed corn or ponding.

“Once a corn plant forms a black layer in the kernel tips, that indicates maturity,” Hurburgh says. “In these wet field situations, you need to get corn out of the field once it reaches maturity, before ear mold starts to become a big problem. When corn reaches black layer and grain moisture is under 30%, you’re better off harvesting it and spending money on artificial drying to get corn down to a moisture content safe for storage.” Of course, the best case is for weather to become mild and dry, but that doesn’t always happen.

Harvesting at higher grain moisture
It costs more to run corn through a grain dryer compared to letting Mother Nature dry it in the field. But using an on-farm drying system or having corn custom-dried at an elevator will protect the corn while in storage. “The worst-case scenario,” Hurburgh says, “is if we have continued rain in September.” That’s been the situation for northern Iowa this fall.

Days with warm temperatures and high humidity are a scenario for field mold of various types to occur. “If you have early-maturing corn, once it’s in the upper 20% moisture range, say 25% to 30%, I recommend harvesting and drying that grain as quickly as possible,” Hurburgh says. “Dry the grain moisture down into mid- to low teens and do it fast. Also, keep in mind the weather we’ve had this September isn’t the best condition to use low-temperature grain drying.”

Before putting corn in the bin, take the moisture content down to 17% or 18% and then finish drying the corn with natural air or a low-temperature drying system later in the fall, Hurburgh says.

If you intend to hold the corn in storage into next spring, dry it down to at least 15% moisture content, he says. You can do that when you put corn in the bin this fall, or if corn goes into the bin at 17% or 18% moisture, be sure to dry it down to 15% in the bin later this fall. “Just don’t try to hold wet grain in these conditions,” he warns.

The corn crop matured quickly this year. It was starting to fire from the bottom of the stalk in early to mid-August in some areas of Iowa: the driest areas. That’s one of the reasons some farmers are seeing shallow kernels, which translates into a lower-than-normal test weight for corn.

“We aren’t having a repeat in 2018, of the good filling of ears and the higher kernel weights we had last fall,” Hurburgh says. “Lower test weight normally means more tendency to spoil in storage.”

Northern Iowa’s wet growing season
While it was dry in southern Iowa, the northern third of Iowa had almost constant rain this growing season. Crops there didn’t advance as fast in maturity with continued wet weather, and some corn ears this fall will likely have a pink mold, fusarium, or a white sheet-like mold, gibberella. They can produce the toxins fumonisin and vomitoxin, respectively.

What should you do if you’re harvesting corn with visible mold on ears and kernels? First, dry it as quickly as possible, Hurburgh advises. Holding wet grain for even a short time can cause more mold and possibly mycotoxin development. Visibly moldy kernels aren’t suitable for long-term storage. So, prioritize getting that corn out of storage and finding a safe and legitimate use for it.

Drying corn in a high-temperature dryer serves an important function; it effectively kills insects and surface mold, in addition to drying the grain. In contrast, corn that’s harvested even at 15% moisture and immediately stored carries some of the highest risk of going bad prematurely because those pests are still alive. Insects are more of a storage risk than a harvest risk.

Use aeration to cool stored grain
Once dried grain is in the bin, Hurburgh recommends using aeration fans to get the grain below 50 degrees F as soon as possible. Then continue to bring it down with weather conditions to eventually 35 degrees or below. Insect and mold activity reduce sharply as stored grain goes below 50 degrees.

In recent years, more farmers are storing corn in big plastic bags. It’s harder to keep corn from spoiling in a bag compared to storing in a bin. Bags can’t be aerated. Thus, corn going into a storage bag needs to be dry.

Hurburgh recommends 1% to 2% lower moisture content compared to storing corn in a bin, and never higher than 15% corn in a storage bag. Also, corn needs to go into the bag at a cool temperature (less than 50 degrees) to reduce the risk of corn spoiling. “That becomes challenging when outside temps are in the 80s and 90s,” he notes.

For more information on grain drying, handling and storage, visit ISU Extension.

Harvest weight limit exemption helps

To help haul this fall’s large harvest in from the field and keep combines moving, Iowa Gov. Kim Reynolds on Sept. 11 signed a proclamation granting a temporary 60-day weight limit exemption for trucks operating on Iowa roads. The waiver began Sept. 15 and expires Nov. 13 unless it is extended.

The 2018 harvest weight exemption increases the weight allowable for shipments of corn, soybeans, hay, straw, silage and stover by 12.5% per axle, up to a maximum of 90,000 pounds, without the need for an oversize or overweight permit.

The waiver applies to loads transported on all highways within Iowa, excluding the federal interstate system. Trucks can’t exceed their regular maximum by more than 12.5% per axle and must obey the posted limits on all roads and bridges.

The proclamation directs the Iowa Department of Transportation to monitor the operation of the waiver to ensure public safety and facilitate movement of the trucks involved in harvest activities. Farmers who are transporting grain are also required to follow their vehicle’s safety standards on axle weights.

“Increasing the weight limit exemption to 90,000 pounds makes harvest more efficient. At the end of the day, the extra weight allowance adds up,” says Curt Mether, president of the Iowa Corn Growers Association. “We appreciate the governor’s help. This exemption is just during harvest, and it helps get harvest finished before bad weather sets in, which can happen if harvest is delayed.”