Frost Risk To Soybean

DR. ANTHONY OHMES

JACKSON, MO.
   The potential for frost in some parts of the region this weekend, has raised some concerns on soybean yield. Generally, temperatures dropping below 30 degrees F for any length of time will damage all plant parts. Frost from temperatures above 30 degrees will typically damage upper canopy leaves. Frost damage begins as water soaked areas on leaves that later turn brown. Soybeans at the R7 stage of development (one yellow pod over 50 percent of plant population) are at the least  level of risk from a frost or freeze and loss is generally minor. Soybeans in the R6 stage of development (swollen green beans in green pods) can sustain damage depending on duration of freezing temperature, usually more loss associated with quality than quantity. R6 soybeans that sustain frost or freeze damage can have a shriveled seed coat and can retain the green color, which 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. Frost damaged soybeans will probably be more difficult to harvest; therefore, combine threshing adjustments may need to be made. ∆
   DR. ANTHONY OHMES: Agronomist, University of Missouri