With delayed planting in Iowa in 2019, it’s important to monitor crop development to determine unique grain drying needs this fall. A lot of the corn and soybeans harvested will come from the field wetter and some less mature than normal. An early frost would complicate the picture even more.

“For soybeans, depending on local weather conditions, we may have plants with a fairly good number of pods, even if the beans were planted in mid-June,” says Charlie Hurburgh, Iowa State University Extension grain quality specialist and director of the ISU Grain Quality Testing Lab. “But be ready to handle wet beans. For corn, I can’t emphasize enough: Farmers need to avoid holding wet grain in bins or wagons for very long. Dry it down to safe moisture content.”

Corn test weights

Pay attention to corn test weight. “That’s a measure of storability,” Hurburgh says. The later-planted corn will have lighter test weight, as kernel fill isn’t as complete at the end of the season. Even corn that was planted on time may have a high yield but lower-than-normal test weight this fall — 52 or 53 pounds or less, instead of 54 to 56 pounds per bushel.

If you have the bin capacity, don’t mix light with heavier test-weight corn. Keep the two in separate bins. Where to draw the line? At 52 or 53 pounds is where Hurburgh normally makes that decision. Corn that’s 53 pounds or higher will keep better in longer-term storage; corn that’s at least 54 pounds per bushel is No. 2 corn, according to USDA grading standards.

“I would separate the lighter test weight corn from heavier test weight corn right away as you put it in the bin,” he says. “And then draw the center core out of all bins to remove the fines, etc. Anything you can do to improve the storability of corn this year will be of benefit.”

If you get 56- to 59-pound test-weight corn, it will keep better longer than the lighter corn. Hurburgh recommends separating corn testing under 53 pounds per bushel from heavier corn this year. 

Soybeans weigh in

What about soybean test weight? Test weight doesn’t mean much for soybeans, Hurburgh says. The top factor for beans is quality: Do you see gray and moldy beans coming out of the field?

Also, pay attention to harvest moisture content. You can dry wet soybeans. If they are below 15% to 16% moisture, you can usually dry them with unheated natural air if it’s lower humidity and not raining. Air-dried beans can store well if dried properly, Hurburgh notes.

Keep in mind if beans start to spoil in storage, it’s very difficult to get that back under control — even with running a grain dryer. The oil in soybeans makes it more difficult to dry them compared to corn.

Crop maturity affects bottom line

ISU Extension ag engineering specialists Kristina TeBockhorst and Shawn Shouse offer guidelines to make grain drying and handling decisions.

Corn damaged by a freeze before reaching physiological maturity is susceptible to low test weight, low quality and high moisture. Even without frost damage, corn maturing later in the year can have issues of high moisture with less in-field drying between maturity and harvest.

The corn in-field drying rate decreases with air temperature. In September, weekly drying is estimated at 4.5 moisture points per week, and in October, November and December, this is reduced to 2.5, 1 and 0.5, respectively.

When harvesting wet grain, you must decide to dry it yourself or pay others for drying. Consider your buyer’s moisture discount factor, or drying charge and shrink factor, as well as your drying system cost and shrinkage loss when deciding whether to sell wet grain, or dry it before selling. Take this example: A seller has 56,000 pounds (1,000 wet bushels) of 20.5% moisture corn, and the current corn price is $3.50 per bushel. Here are your choices:

Sell wet grain “as is” with a moisture discount. If the buyer is assessing a moisture price discount of 2% for each moisture point above 15%, the discount would be 5.5 moisture points times 2% for a total discount of 11%, making the discount $3.50 times 11%, or 39 cents per bushel. In this case, the seller would see a net revenue of $3,110, or $3.11 times 1,000 wet bushels.

Sell wet grain “as is” with a drying charge and shrink factor. The buyer may instead use a combination of drying charge and shrink factor. If the buyer is charging a drying fee of $0.048 per wet bushel per point of moisture removed, the drying charge would be $0.048 times 5.5 moisture points times 1,000 wet bushels, or $264. If the buyer uses a shrinkage factor of 1.4% per point above 15%, this would reduce the seller’s bushels by 77 bushels, or 1.4% times 5.5 moisture points times 1,000 wet bushels, leaving 923 bushels of dry grain. The net revenue would be $2,967, or 923 bushels times $3.50 minus $264.

Dry on-farm before selling. Consider the drying cost per bushel of your system, as well as shrinkage loss from the drying process. Using the Ag Decision Maker spreadsheet “Corn drying and shrink comparison, A2-32, and a propane cost of $1 per gallon and electricity cost of 14 cents per kilowatt-hour, a high-temperature drying system wouuld be 3 cents per bushel per point of moisture removed. The drying cost would be equal to $165 ($0.030 times 5.5 moisture points times 1,000 bushels).

Drying shrinkage loss is mostly due to water loss, but includes handling (dry matter) weight loss. A 56,000-pound load of 20.5% moisture corn has 11,480 pounds of water and 44,520 pounds of dry matter. After drying 5.5 moisture points, there will be 52,376 pounds (44,520 pounds divided by 0.85). Handling loss from on-farm drying has been measured between 0.22% and 1.71% of wet bushel weight. Assuming a common handling loss of 1%, handling shrink is 560 pounds. Dry weight to sell is 51,820 pounds, or 925 bushels (52,376 minus 560).

Also, assume additional transportation costs of 1 cent per bushel per mile, which would be $40 to haul 4 miles to the on-farm drying system. Net revenue then becomes $3,033 (925 times $3.50 minus $165 minus $40). Consider extra drying costs if planning to store more than six months at a lower-moisture content.

This example is for illustration only. Ask your buyer about moisture discounts or drying charges and shrink factors. Use your actual costs for propane and electricity.

Estimate propane needs for a high-temperature dryer by using this equation: 0.018 gallons times bushels dried times moisture points dried. While 0.018 gallons is an average propane usage estimate, this value may range from 0.010 to 0.025 gallons per bushel per moisture point, depending on the drying system and outdoor temperature.

If harvest is delayed later into the fall, consider that the drying cost of a high temperature dryer increases by around 14% with every 20 degree decrease in average outdoor temperature.

For more information

Frost Damage to Corn and Soybeans, PM 1635, Charles Hurburgh and Garren Benson, 2012

Soybean Drying and Storage, PM 1636, Charles Hurburgh, 2008

Estimating the Cost for Drying Corn, A2-31, William Edwards, 2014

Corn Drying and Shrink Comparison, A2-32, William Edwards, 2014