Get Ready for Harvest

August 29, 2009 02:32 PM

Slowing down your combine reduces cracking of high-moisture corn. It's well worth it because cracks will haunt you all through drying and storage.

Growing a high-yielding corn crop is only half the battle. Gathering that grain, drying it and storing it is the other half. This year, for many farmers, the harvesting-drying-storing scenario will be more challenging than usual
because they'll be dealing with wet corn, resulting from late planting.

Here are some things to think about as you plan how to minimize grain damage and preserve yield.

Nature's way.
If possible, let Mother Nature do your drying for you. "We would rather see farmers wait to harvest than bring in wet corn,” says Jack Trainor, an elevator operator in Illinois. "Farmers sometimes think we make money drying corn; but in reality, we don't like to receive it. The quality disappears at more than 20% moisture; it's expensive to dry and to maintain in the bin for several months.”

In North Dakota, where farmers slogged through a late wet harvest in 2008, "whether to leave grain to dry in the field was a big issue,” says North Dakota State University ag engineer Ken Hellevang.
"In a northern climate like ours, you have to weigh the amount of drying occurring in the field against typical field losses from delaying harvest,” Hellevang continues. "Through early October, there's usually enough drying occurring to justify leaving the corn out there. But by late October, the temperature usually is so low that less and less natural drying occurs.”

Keep tabs on how much drydown is occurring, Hellevang suggests. "Most Extension sources can tell you the typical drydown rate for your area,” he says. "And you can check what's happening with your moisture. Your meter is calibrated for dry corn, so at 25% or 30% moisture there will be a certain amount of error. But you can still get a relative idea of how the moisture content is changing.”

Hybrid Differences
Some hybrids withstand the stress of high-heat drying better than others, says Jack Trainor of Trainor Grain and Supply Company in Forrest, Ill. "The difference shows up when you dry corn harvested at more than 20% moisture,” he says. "Some hybrids can be dried at 16% moisture and others can't. The result is stress cracks and loss of grain quality.”

You might ask your seed salesman if he knows which of your hybrids are less tolerant to high-heat drying. As you combine, you can note which ones dry down slowest in the field. All other factors being equal, those might be hybrids to shy away from next year.

How long to store? Wet corn will be just as challenging in the bin as it was in the combine. Exactly how long you can store corn at various moisture levels varies somewhat by latitude and temperature, so check with your local Extension agent and elevator operator and heed their advice. In central Illinois, Trainor advises against holding corn at more than 15% moisture.

"Trying to hold wet grain into spring and summer just doesn't work,” Trainor says. "Corn that dries naturally and comes out of the field at 16% moisture will keep as if it was 13%. However, corn dried from 26% to 15% will not keep well—and drying 16% moisture corn is difficult, even with an elevator's drying system.

"If you plan on storing grain through the winter months, dry it below 15% moisture,” Trainor continues. "We assume that if we put corn into a bin at 15% moisture, it will come out at 14½%. But drying depends on the weather. This year, in this area, corn came out at 15%, at the same moisture it went in last fall, because we had no drying weather.

"If you put corn in wet, consider moving it early in the spring, rather than storing it into summer,” Trainor adds. If you think the price will go up, and if you don't mind margin calls, buying the crop back on the futures market is an option.
Lower Heat, Higher Quality
"While mechanical damage increases at higher harvest moisture levels, how corn is dried also influences cracking,” says North Dakota State University ag engineer Ken Hellevang. "Rapid drying at high temperatures and rapid cooling increases cracking. Dryer designs also affect cracking.”

To preserve quality, Ray Bok of Sherwood, Ohio, dries corn with as little heat as possible. "With corn at 25% moisture, high heat causes cracks and creates fines,” he says. "The less heat, the higher the grain quality and the easier it is to store.”

Using a continuous-flow tower dryer, Bok holds heat to 180°F to 200°F. "Our dryer salesman recommended 225°F to maintain capacity,” he explains. "We've learned that the lower temperature preserves quality. It does take longer to dry, though.”

"I encourage farmers to use the maximum drying temperature that will not damage the corn,” Hellevang says. "The best energy efficiency and dryer capacity will be obtained using the maximum temperature, but quality can be affected. At high moisture contents, corn is in the dryer longer, so the dryer temperature must be reduced to prevent damaging the corn.”

Watch your bins.
In large grain bins, monitoring systems, such as temperature cables, are essential, Hellevang says. But they are still only a tool.

"You still need to physically check the grain, at least every couple weeks when temperatures are changing, from the time you put the grain in until it is cool,” Hellevang says. "Be prepared to run aeration fans, if needed. After the grain has cooled down, checking it once a month may be enough. But if temperatures start to warm up in February, inspect it again.”

The drawback to temperature cables, Hellevang says, is that they only measure the temperature of grain very near the sensor. "If grain were used as insulation, 2' of it would have an R value of 24—more insulation than is used in most homes,” he says. "In a study at Purdue University, researchers put bags of deteriorating, heating grain 2' from temperature cables, and the heat did not show up.”

Check bins periodically the way you always have, Hellevang advises—by looking for signs of moisture, heating, surface crusting and off odors.

"There's no substitute for checking bins,” agrees Ray Bok, of Sherwood, Ohio. He spotted grain going out of condition after an unexpected week of 90°-plus temperatures in early June.

Bok also discovered a column of damaged grain in the middle of a bin, which temperature cables had not detected. "It was caused by beeswings cutting off the flow of air,” he says. "You need to remove those fines during harvest if possible.”

Speed kills.
If you expect to deal with wet corn this fall, "plan for a lengthened harvest,” says Dan Klein, a combine marketing specialist for Case IH. "Everything takes longer with wet grain, from augering corn into the grain tank to moving it through the dryer.”

Especially if you're anticipating high yield and to wet corn, "slow down the combine 1 mph or so,” Trainor advises. "Overloading your combine leads to cracked grain and cobs, which will haunt you through drying and storage. Cobs and cracked grain will cost you financially when you're docked at the elevator or terminal.”

Tips from Harvesting Experts
Corn's journey from field to bin to market begins with your combine, which means checking settings and performance in every field. Below is advice from harvesting experts on maintaining yield and quality in tough conditions.

"Each field will harvest differently, due to differences in varieties and changing moisture levels,” says Kent Hawk of John Deere.

"We have noticed that, with new corn genetics, variety and soil conditions affect harvesting performance,” says Dan Klein of Case IH. "With the same hybrid, stalks may have more durability in a clay soil that holds more moisture, compared to a sandy soil.”

"If you're operating a brand-new machine, check the performance and settings of both the combine and the header after 50 to 75 hours of break-in time,” advises AGCO's Kevin Bien.

Kent Hawk, field service supervisor, John Deere
Conduct a preseason inspection. On a conventional machine, check the concave for wear and look for rounded-over edges on the crossbars. On a rotary combine, check the threshing elements for worn and rounded-off edges.

It's critical to have the concave level from side to side when you change the spacing for wetter or drier corn. If the concave isn't level, it may do a good job on one side but crack kernels on the other side.

At the corn head, especially if you are harvesting at 28% moisture and higher, pay attention to deck plate spacing. As corn gets drier, you may want to take in a little trash to avoid kernel damage.

Avoid running excess free grain in the tailings return. Most operators will close down the sieve to clean up the grain tank better, especially from broken cobs. Recycling free grain back into the separator will increase grain damage.

Minimize breaking cobs up front by adjusting the deck plate spacing, the feeder house chain speed, the rotor/cylinder speed and the concave clearance. Variety and cob diameters differ, so check machine performance in every field. This year will be a challenge with uneven stands, which leads to different ear sizes. 

Kevin Bien, product marketing manager for Gleaner and Massey Ferguson combines, AGCO Corporation
Today's combines record settings in all areas of the machine, so start by checking settings from the previous year. If you don't have the capability, refer to the settings guide in your operator's manual.

Start with your header. Check and adjust the stripper plates and gathering chains, and inspect the condition of the knives. Set these components to the manufacturer's recommended setting and then adjust them in the field.

In the field, watch for symptoms such as grain loss; then make small subtle changes one at a time. Observe the effect until you fix the problem.

Concave clearance is important on rotary combines. If you're cracking grain, open the concave or adjust the rotor speed. If you're breaking up the cobs, your settings are too aggressive; try increasing the concave clearance or slowing the rotor in 10-rpm increments.

If there's too much grain going over the top chaffer of the shoe, open the chaffer in small increments. If you're getting large pieces of debris in the grain tank, close the chaffer a bit. If too much clean grain is going into the tailings return, open the sieve.

Dan Klein, combine marketing specialist, Case IH
Worn or damaged combine components affect grain quality and overall performance. Grain damage may not look too bad in the combine hopper, but it will
affect grain through drying and storage.

Damaged threshing components will crack grain. Before harvest, look for worn parts. Check the impeller blades on the front of the rotor on a rotary combine, and inspect the threshing elements on conventional combines.

Ensure the concave and rasp bars are in good shape; you'll want to run the rotor a little faster and the concave a little tighter in tough conditions.

In the field, farmers slow down the rotor or open the concave to reduce grain damage. But if you set the rotor too slow or too wide, especially in tough conditions where more green leaf and stalk material go through the combine, you can block the concave. If free grain can't get through the concave into the cleaning system, you can damage grain and lose it out the rotor. You may need to slow down your groundspeed.

With tougher greener stalks, you may want to run wider stripper-plate settings to let stalk and leaf material be pulled through the knife rolls, rather than go through the combine. In the cleaning system, running wider sieve settings and a higher fan speed can save grain and blow out more leaf material.

Doing a "kill stall” in each field (see operator's manual) gives a snapshot of your combine's performance. You want grain to be distributed evenly throughout the cleaning system. Changing the rotor speed and concave clearance settings can help.


You can e-mail Darrell Smith at

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