Assess Freeze Damage To Soybeans Before Harvest And During Drying Says MU Extension Specialist
LAMAR, MO.
A late maturing season and freezing temperatures have raised some concerns about the effect on soybean yield according to Jill Scheidt, agronomy specialist with University of Missouri Extension.
“Generally, temperatures dropping below 30 degrees Fahrenheit for any length of time will kill soybean plants,” said Scheidt.
Soybeans at the R7 stage (one yellow pod over 50 percent of plant population) are at the least level of risk from a frost or freeze and loss is minor. Soybeans in the R6 stage (swollen green beans in green pods) can sustain damage, usually more loss associated with quality than quantity.
According to Scheidt, R6 soybeans that sustain frost or freeze damage can have a shriveled seed coat and can retain the green color. The color will potentially can become lighter over time if stored. Soybeans in early stages than R6 can sustain significant losses, especially if temperatures fall enough to result in complete foliage loss.
If a soybean field sustains severe, frost/freeze damage soybeans should be harvested between 16 percent and 18 percent moisture and then dried to below 13 percent for safe storage. Shatter loss can increase in frost/freeze damaged soybeans when allowed to field dry below 16 percent. The longer soybeans stay in the field after maturing, the greater the risk of shattering.
“Frost damaged soybeans will probably be more difficult to harvest so make some combine threshing adjustments. If soybean seeds and pods are mature, but stems are green, be patient. The harvest process must be taken much slower to allow the residue to clear the combine. Freezing temperatures do not kill stems quickly, so it is better to run at a slower pace than wait for stems to dry and risk shattering,” said Scheidt.
SOYBEAN DRYING
In-bin drying with natural air by running fans is usually enough to drop the moisture two to three points when air temperature is 60 degrees, or above and relative humidity is below 75 percent.
Beans above 16 percent moisture should have fans running continuously and may need supplemental heat. However, be careful since soybeans are more fragile than grain crops such as corn. Air temperature increases of 5 to 15 degrees is sufficient.
“Relative humidity should always be maintained about 40 percent to protect the seed coat, and relative humidity is cut in half for each 20 degrees that the air is warmed,” said Scheidt. ∆