Air-dry a million bushels? You bet

Jim Purlee eased his way into air-drying grain. He started 15 years ago. By 2002, he’d cut himself off from all gas drying. Today he dries nearly a million bushels of corn with nothing but air. And it costs him just 2½ cents a bushel, on average.

Purlee is, by conventional agricultural wisdom, somewhat unconventional. While many larger Illinois farmers have moved to on-farm commercial-type storage, complete with tower dryers and wet holding bins and more, Purlee has taken his 8,000-acre operation in the opposite direction. Make no mistake, however. He still utilizes storage. He just dries the grain a little differently.

“A lot of our farms have come with a handful of small bins,” Purlee says. “Years ago, we got a farm with three bins, and they had full floors. We discovered if we put corn in at 19% to 20%, turned on the air and left it for 30 days, it worked. And electricity is generally cheaper than gas for us.

Key Points

Jim Purlee air-dries crop with 1.5 million bushels of storage.

It costs him 2½ cents a bushel; Tombaugh pays 8 to 12 cents.

Purlee begins harvest when grain is 19% to 20% moisture.


“We’ve kind of patterned our drying system after that one farm, where we found it works.”

Purdue University’s Richard Stroshine, ag engineering professor, says the main reason most folks avoid air-drying is lack of capacity to dry large volumes fast.

“Air-drying may take several weeks, and takes a significant amount of management,” he says. “So the very large farmers do high-temperature, cross-flow drying because they have thousands of acres to get harvested, and they need to get it done quickly.”

Volume control

Storage isn’t a problem, however, for Purlee, who harvests a total of 1.2 million bushels of corn and soybeans, and has 1.5 million bushels’ worth of storage on his Galesburg operation. That storage comes in the form of some 50 bins, ranging in size from 10,000 to 100,000 bushels. Over time, he’s added full floors to older bins equipped with concrete floors, and added fans and vents, as well.

“You need about ¾ hp per 1,000 bushels of corn,” Purlee says, “so a 25,000-bushel bin needs a 20-hp fan.” He also recommends plenty of roof vents, to the tune of eight vents per 20-hp fan.

Larry Tombaugh, a Streator farmer and small-business owner, climbed on the air-dry bandwagon two years ago and even became a dealer for CMC’s high-pressure curing system. Tombaugh harvests and dries even more aggressively than Purlee, starting when corn is 25% moisture.

He allows that air-drying has been most popular among smaller farmers with smaller bins — 60 feet in diameter or less — and that lower humidity helps. Indeed, CMC was founded based upon Canadian ideas, and has seen greatest growth in the High Plains and in areas where milling crops like rice and canola demand high grain quality.

Purlee admits bigger bins are more of a challenge to manage, but he’s done it. He’s equipped his 100,000-bushel bins with two 30-hp fans, and admits that’s “pretty minimal.”

If he has wetter corn, he’ll take it to his “short, fat bins” so corn is only 10 feet deep.

“When you put corn in the bin, you don’t want to ignore it,” Purlee adds. “You want to see if it’s drying. Sometimes you can core the center, and put it in another bin. Just moving corn around helps it to dry. Don’t have to every year. Every year is different. Some years you put it in and turn the fan on, and in 30 days it’s perfect.”

Bottom line

Tombaugh says some farmers don’t want that kind of risk, and he understands that. But he also looks hard at the bottom line. By his figures, drying with LP costs 30 cents to bring corn down 10 points of moisture. His high-pressure air-drying bins can take 10 points off in nearly 30 days for 8 to 12 cents per bushel, and he claims it adds 2 pounds of test weight.

Tombaugh adds that the secret to getting air-drying to work is really high air pressure going through a level, clean grain sample. He runs a 13-inch auger with 16 feet of sieves cut into it. He also prefers to harvest corn at higher moisture, taking it out of the field at 25% and using high-pressure fans to push 2 cubic feet per minute (or more) per bushel through the corn for a month, taking it down to 15%. “It actually costs the same to take it down from 25% as it does from 21%, so you can get out there earlier.”

For Purlee, waiting is a matter of discipline.

“We have learned we’re better off letting corn dry in the field a little more, then air dry it,” he describes. “It takes discipline to wait a week to harvest. You have to find something else to do!”

Tips for air-drying success

Want to dry 25% moisture corn? Check out this advice from Purdue’s Richard Stroshine:

Supply 3 cfm per bushel when the bin is full.

Consider supplemental heat in a bad drying year, such as 2009.

Try “layer drying.” Place a 2- to 3-foot layer of corn in the bin; dry it, and then add another layer. Vary depth of each layer based on airflow capacity (cfm/bu), harvest moisture content, weather conditions and airflow when bin is full.


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Well-managed:
“Don’t kid yourself,” says Galesburg farmer and air-dry advocate Jim Purlee. “You need a good fan and a floor. Don’t put the corn in until it’s 19% to 20%. You can pick in the low 20s; just fill the bin a third full and push the air through it.”

 

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JUST VENTING: Larry Tombaugh will tell you, air-drying is all about the vents. He recommends one vent per 2 hp of fan, plus a peak vent. His 42-foot bin is outfitted with two 30-hp fans, or “air pumps.” CMC claims its fans operate at consistent pressure, which lets them move high volumes of air at peak efficiencies. Airplane-type fan blades don’t hurt either; in fact, Tombaugh says he can’t kick on the fan with an empty bin, or he’ll risk blowing the floor off its supports.

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FINE FLOOR: Tombaugh uses CMC’s “no fines” floor, which has louvered perforations designed to keep fines from dropping through. He also uses temperature sensors, which drop down from the bin ceiling to within 3 feet of the floor, allowing him to closely monitor conditions throughout the bin.

This article published in the September, 2011 edition of PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.