Warm, dry fall weather can result in soybeans being harvested well below the market moisture content of 13 percent, according to Ken Hellevang, the North Dakota State University Extension Service's grain drying expert. In Eddy County, for example, harvested soybeans have been in the 8-9% range.

"On a 40-bu. crop, that equates to around 2 bu. of lost weight due to the beans being so dry," says Eddy County Extension agent Tim Becker. "At $11-12/bu., that’s around $20-25/acre in lost moisture."

While adding water to soybeans to increase their moisture content is illegal, producers can boost the moisture content by aerating the beans with humid air, provided they have enough time and a high enough airflow per bushel, Hellevang says.

If a bin of soybeans is aerated continuously, the beans would lose moisture during periods of low humidity and gain moisture when the humidity is high. Therefore, producers would need to make sure to operate aeration fans during weather with an average relative humidity of about 70% if they want to recondition soybeans to 13% during normal fall temperatures of 30-60° F.

The moisture doesn't change throughout the bin during reconditioning, Hellevang notes. Instead, a rewetting zone develops and moves slowly through the bin in the direction of the airflow.

In most cases, fall weather doesn't provide enough hours of high humidity to move the rewetting zone through the bin. If the fan is operated during high humidity, the soybeans in parts of the bin would be too wet to be stored safely.

"Mixing the wet layers with the dry layers would be best to reduce spoilage risk and avoid drying charges for the wet layers when the beans are sold," Hellevang says.

Bin dryers equipped with stirring augers work well for reconditioning soybeans. Emptying the bin and moving the beans through a grain-handling system will provide only limited mixing.

In beans with moisture contents of 10% or less, controlling the aeration fan so it runs only when the relative humidity of the air reaching the beans is greater than about 55% should result in rewetting. One way to accomplish that is to use a humidistat to turn the fan on any time the humidity is above 55%. Another option is to run the fan only at night because that's when humidity almost always is higher.