Northern and eastern Kentucky received as much as 6 to 8 inches of rainfall the last 7 days. Some cornfields were flooded. The heavy rains north of the Ohio River will add to the river’s water volume, potentially flooding fields downstream.
If flooding fully submerges corn in fields with soil temperatures above 70 degrees Fahrenheit for more than 24 hours, the corn will not survive. For corn at blacklayer, seed fill was complete. The flooding event, itself, will not affect seed fill. For corn that was near blacklayer, these plants will die prematurely, reducing yields.
In either scenario, flooding will slow grain drying and possibly complicate harvest.
Flooded corn is more prone to stalk rot development. Fungi and bacteria can colonize weakened stalks and roots, contributing to stalk rot and lodging when waters recede. Check plants for stalk rot in several areas of the field by using a push test or a pinch test. To conduct a push test, stand facing the corn plant and push the stalk with one hand at a 30-degree angle at eye level. If the stalk breaks or does not return to standing, the stalk integrity is compromised.
If the corn is ready to harvest, and stalk rot is suspected, a pinch test may be used to reduce the amount of breakage from a push test. Pinch the stalk somewhere between the lowest two internodes. If you feel the stalk “give” or compress under your fingers, the stalk integrity is compromised.
Lodged corn that comes in contact with soil can also lead to secondary ear rot development and reduce grain quality. If 10 percent of the stalks tested are compromised, the field should be harvested as soon as possible to avoid yield and grain quality losses due to late-season lodging.
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Quick grain harvest and immediate grain drying is the best option to minimize losses from flooding. If grain drying is not an option, then these fields cannot be harvested until grain approaches harvest moistures near 15%. Most grain elevators likely will not accept corn at very high moistures.
The greatest risk to ensiling corn comes from the mud left by the receding waters. The mud may contain Clostridium bacteria, which can interfere with fermentation. This can lead to botulism toxins. Any flood-damaged corn that is ensiled should be bagged separately, marked and sampled for potential toxins before feeding.
Good ensiling techniques reduce the risk of poor fermentation, but they do not prevent contamination from the mud. For corn with heavy silt residues, perhaps harvesting and bagging high moisture grain is the better option. Again, store any flood-damaged corn separately from other corn. Monitor it for any toxins before feeding.