Wallaces Farmer

Many Iowa farmers are harvesting soybeans above 13% moisture content, putting them in the bin and turning on the aeration fans.

October 23, 2009

4 Min Read

Many farmers across Iowa are harvesting soybeans at a moisture content above 13%. They are putting them in the bin and turning on the aeration fans.

With rainy, cloudy weather and even some snow in some areas of the state during the first half of October, soybeans are coming out of the field a little wet this fall. "Much of the soybean grain has been 14% to 15% moisture as it's been harvested here in our area," says Paul Kassel, Iowa State University Extension field agronomist at Spencer in northwest Iowa.

Kassel and other ISU Extension specialists have been fielding questions on storing soybeans, drying soybeans—something farmers in Iowa don't usually have to do in falls with normal harvest weather. Conditions for soybean harvest are not ideal this fall, no matter how you look at it. As one farmer asked, "What can you do? You have to harvest even if it isn't ideal conditions."

Soybeans stored on the farm need to be aerated
Kassel says there's roughly a 2 bushel per acre loss when 15% moisture content soybeans are delivered to the elevator—if the elevator assesses a 3% dock per point of moisture. But, you need to remember there is also an invisible loss if soybeans are harvested too dry—which happens in a normal fall but probably won't happen this year. "Actually, we have some losses whenever we harvest soybeans," he notes. "It's difficult to get perfect harvest conditions for beans." "Soybeans stored at home should be aerated," advises Kassel. "Aeration is always important with any crop – but since some of these soybeans are a little wet – aeration will be really important. I'm advising farmers to let those aeration fans run – and keep that in mind as we go through the rest of the fall and winter."

Charles Hurburgh, a grain quality expert and director of the Iowa Grain Quality Initiative at ISU, offers the following guidelines and recommendations for aerating corn and soybeans.

Aeration Practice
Phase 1: Fall Cool Down
   • Lower grain temperatures in a stepwise fashion
         • October 40-45 F
         • November 35-40 F
         • December 28-35 F

Phase 2: Winter Maintenance
   • Maintain temperatures with intermittent aeration
         • January, February 28-35 F

Phase 3: Spring Holding
   • Keep cold grain cold
         • Seal fans
         • Ventilate headspace intermittently

Soybeans can be dried. But most farmers will not do it, notes Kassel. They're just not used to drying soybeans. For proper storage, soybeans need to be dried to at least 13% for short-term storage and at least 11% for long-term storage.  Soybeans harvested at less than 15% moisture can generally be dried with fans that are sized for routine aeration (0.1-0.2 cfm/bu.).  Above that, likely requires low-temperature drying. 

"The last half of the 2009 soybean harvest is likely to be wet, over 14% moisture content, with many reports already of 18% to 20% moisture soybeans coming out of the field," says Hurburgh. Soybeans dry more easily than corn so air alone, or heat no more than 120 degrees F will be adequate, he says. Monitor the drying frequently to prevent overdrying of soybeans.

An ISU Extension publication, :Soybean Drying and Storage:, PM 1636, has more information. Go to  www.extension.iastate.edu/Publications/PM1636.pdf.

Wet soybeans should not be held in bunkers, piles, flat storages, sheds or other structures where airflow is not well distributed. 

Which beans should go into storage, which should be moved?
"Be selective about what beans are placed in storage versus moved at harvest," advises Hurburgh. "Deliberately decide which bins are going to be kept into the summer. Remove the center core and use a grain distributor if possible. Check your stored grain at least every two weeks, with some way to take grain temperatures. If a slow rise is noted, then you should aerate. If a hot spot starts, move the grain out. It is very difficult to control soybean spoilage once it has started. Oil rancidity becomes a major problem."

Wet soybeans will happen, and they are a reality especially in eastern Iowa this fall. Patience will be important because the grain handling system is also facing a large, wet corn crop in the same areas. Hurburgh says soybeans can be dried with natural air and heated up about 120 degrees F; soybeans respond quickly to air conditions. On farm drying is likely to be profitable because the grain market does not have the capacity to handle both wet corn and wet soybeans.

Frost damage occurred in later planted soybeans in some areas of Iowa this fall; the best strategy is to aerate and store for 40 to 60 days before selling. The greenness may subside enough to be below the color threshold of the USDA grain grades. In cases of dispute over grading, Hurburgh says you should submit the sample to a USDA licensed grading agency for resolution. Protein levels are likely to be below average; oil levels above average in Iowa soybeans for 2009.

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