Soybean Dry Down

Knowing current soybean moisture levels and how fast they naturally dry down in the field can help with scheduling harvest and planning for storage.

Mark Licht is an Extension cropping systems specialist at Iowa State University, and part of a team that conducted research on dry down rate. He says day length and environmental conditions play into the natural drying process.

"One of those drivers really is, what is the air temperature, what is the relative humidity? And when we are reaching soybean maturity earlier in the fall, we have longer daylengths and that drives our average daily temperature so we have a better drying condition," says Licht.

Soybeans are considered mature when they are done accumulating dry matter and seed moisture rapidly decreases. Depending on the year and the genetics, he says they will be at 55%-65% seed moisture.

The easiest way to tell if they’re mature is to look at the color of the bean pods.

"We generally are looking for that mature soybean pod color, that brown, tannish-color pod up and down the main stem, and that’s what we would typically say is the seed maturity. That gets us away from having to basically hand pull the pods apart, get the beans out and do the moisture on them," he says. "We can just use a visual assessment instead, and that’s fairly accurate."

Licht says the rule of thumb is to wait ten days after maturity to go in and harvest. By then the dry down rate slows or stops completely, stabilizing at about 13% moisture.

Learn more about the soybean dry down process