North Dakota State professor reviews reconditioning for dry soybean cropWritten by Natasha Wheeler
Soybean harvest is nearly complete this season across the Midwest, and in many cases, the harvest came in with low moisture content. Ken Hellevang, an agriculture and biosystems engineering professor at North Dakota State University spoke with realagriculture.com on Oct. 21 about reconditioning the beans.
“If the beans are exposed to air that is dry, moisture moves from the bean to the air. If it’s exposed to air that’s at a higher humidity than the beans, then the moisture goes from the air to the soybeans,” Hellevang explained.
The goal is to increase the moisture content of the soybeans, which may be as low as nine percent, back up toward the market standard of approximately 13 percent moisture content.
“During the daytime, it might be warmer and dryer, with cooler and higher humidity at night, but we are looking for an average of roughly 70 percent humidity. That will provide us with soybeans that are about 13 percent moisture,” he commented.
Hellevang warned producers against running fans when the air is too humid, such as when the weather is rainy or foggy.
“If there is very humid air outside, that air goes into the bin and the reconditioning takes place in a front that gradually moves through the bin just like a drying zone. We can end up with a layer of wet beans that would be at a high enough moisture content that spoilage could become an issue,” he said.
Humidity can be monitored manually or producers can use automatic fan systems that turn on and off depending on the relative humidity of the outside air.
Another concern that Hellavang mentioned was the stress that is applied to the bins as the soybeans absorb more moisture.
“When we are drying the beans, there is a shrinkage that takes place and the beans will settle in the bin. When the moisture content increases in the soybeans, there is an expansion that takes place, but unfortunately, the beans don’t increase in depth so that force gets transferred to the bin wall,” he noted.
In some cases, that force can be enough to damage the soybeans or possibly even rupture bins.
“There are a number of things that people have tried over the years that have worked, such as periodically unloading a load or two of beans as that reconditioning is taking place,” Hellevang remarked.
Pulling air through the beans from the top and removing the top layers as they are reconditioned has also been successful for some producers.
“A person needs to really approach it with some care and close monitoring to make sure that we are not creating a damaged bin as part of that reconditioning process,” he stated.
Producers who choose to recondition their soybeans should take note that the process takes some time, and it takes longer if the air is colder or dryer.
“Just like what we would do with natural air-drying, it’s a relatively slow process. We need a bin that is set up to move lots of air, and we are probably looking at a month of fan time to dry beans,” he commented.
Although there are added costs to dry the beans, Hellevang noted that the added market value is typically worth the process of reconditioning.
“It depends a little bit on what Mother Nature will give us in the next few weeks, but there could be a benefit to reconditioning soybeans yet, for a little bit of time this season,” he explained. “The closer we get to freezing, the less efficient this process is going to be.”
Otherwise, producers might consider cooling and then storing the beans over the winter.
“We can do the same reconditioning process in the spring once temperatures are moderated,” said Hellevang.