Prolonged wet weather increases chances that grain crops will sprout before they can be harvested this fall, said a University of Missouri Extension agronomist.

Plentiful moisture and temperatures above 50 degrees are what farmers want after planting in the spring, not before harvest in the fall, said Bill Wiebold, crops specialist. “Sprouting could ruin the grain quality.”

Most years, the corn and soybean crop are harvested and in the bin by mid-October. However, the wettest October in 70 years has stopped most attempts to harvest grain across the state.

Statewide average rainfall for October approached 9 inches, three times normal, said Pat Guinan, MU Extension commercial agriculture climatologist.

If moisture enters the corn husks or soybean pods, the conditions for spouting increase as temperatures remain mild.

“The minimum temperature for corn seed germination is about 50 degrees or a little cooler,” said Wiebold. “Unfortunately, water for germination has been abundant this fall. I’m seeing more of the corn ears remaining upright, leaving an opening for moisture to reach the kernels.”

Normally, corn ears droop over and hang down at maturity. The husks around the corn ear shed water, protecting mature kernels from moisture that may cause germination.

Soybean seed is protected by a pod, but alternating wet and dry periods cause swelling and shrinking that can break the pod, admitting moisture. Soybean seed remaining in the pod can sprout. The greater danger is that the soybean seed in shattered pods will fall to the ground and be lost before harvest.

“Both corn and soybean seeds possess mechanisms that prevent sprouting before maturity,” said Wiebold. “The primary defense is a growth hormone, abscisic acid (ABA), which peaks during the middle of seed filling but decreases as seeds mature.”

For most corn and soybean plants, only small amounts of ABA remain in the seed by harvest time. The loss of ABA allows the seed to be used to plant the next crop. ABA is water-soluble and will leach out of wet kernels.

“Unfortunately, this means that with the right moisture and temperature conditions, seeds from normal corn or soybean plants can germinate on the ear or in the pod,” said Wiebold. “Premature sprouting is quite damaging to grain quality. During germination, seeds release enzymes that break down carbohydrates, proteins and fats. This breakdown releases free sugars and other nutrients from the kernel.”

Those sugars, especially in moist conditions, provide food for fungus and mold growth. Some of those pathogens produce toxins harmful to livestock, making sprouted seeds worth less as livestock feed. Sprouted kernels increase storage problems, inviting further fungal growth and insect feeding.

As long as weather conditions remain unchanged, there is not much that farmers can do about sprouting losses, said Wiebold.