By Katie Nichols
Soybean harvest has begun in some areas of Alabama, and harvesting will continue to increase as producers move toward the month of October.
An Alabama Cooperative Extension System crop specialist said soybean harvest often sneaks up on busy producers. Making preparations for soybean harvest ahead of time may save producers time and money down the road.
Physiological Maturity
Soybeans are generally considered fully mature at the R6–green bean or full seed–stage. At this point only about 60 percent of the bean’s dry matter is in the seed. The plant is still working to fill in the seed.
While the beans may be fullsized, Dr. Dennis Delaney said it is important to check the white membrane where the seed attaches to the pod.
“If the membrane is still intact, the pod is still adding dry matter to the seed,” Delaney said. “When it starts to separate or decompose, the seed is beginning to dry out or reaching physiological maturity.”
The sooner the beans can dry in the field for harvest, the better. Moisture after physiological maturity in a soybean field can cause issues.
“Soybean dry matter, or yield, peaks at physiological maturity,” he said. “After maturity, the bean dry matter and quality only decreases .”
Soybean dry matter is decreased when there is enough moisture for respiration or seed decay organisms.
Delaney said even heavy dews can increase the seed moisture enough to have a negative effect on soybean yield over time.
Harvest Moisture Content
Standard soybean moisture is 13 percent. But at buying points, discounts begin when moisture content above 13 percent. Delaney said usually there is a little bit of leeway with a moisture percentage higher than 13 percent, but there is almost never a bonus for soybeans with lower moisture content.
Delaney said soybean harvest can actually begin with a moisture content much higher than 13 percent—between 16 and 22 percent.
“We have harvested soybeans with 18 to 19 percent moisture content pretty easily if the pod walls are dry,” said Delaney. “Even though the beans may have moisture in them, they will thresh at 18 to 19 percent.”
With a thin pod wall, moisture levels can fluctuate rapidly. This is one of the major differences between corn and soybeans.
Delaney has harvested several test plots where the high moisture content is drastically reduced throughout the day. He said it is good to begin harvest at a higher moisture percentage. Later in the day, the moisture content diminishes and the load’s average moisture content is about 13 percent.
Harvest Delays and Losses
“The longer harvest is delayed, the more harvest losses increase,” Delaney added.
Two common issues with late harvested soybeans are lodging and shattering. Lodging can be a leading cause of mold and seed loss at the header. Shattering losses increase as seed moisture decreases.
“When producers are in the field, it is important to keep an eye on losses,” Delaney said. “No operation is going to be perfect, but aiming for losses of less than one bushel per acre should put producers in a comfortable spot.”
Losses of about 4 to 5 beans per square foot is equal to one bushel per acre. These losses can occur at the combine header and inside the combine. In the field, count the number of beans on the ground behind the combine for total loss.