Although spring flooding of crops is a much more common problem, heavy rainfall in late summer and fall occasionally leads to flooding of fields at or near crop maturity. The extent of damage from fall flooding depends on the crop, stage of maturity, depth of flood waters, period of flooding, amount of lodging caused by flowing water, and other environmental factors. This Field Facts will discuss fall flooding damage to corn.
Milk line just starting to appear.
~400 GDUs remaining to maturity
Yield Loss ~ 35-40%
1/2 Milk Line
~200 GDUs remaining to maturity
Yield loss ~ 12-15%.
BlackLayer or "No Milk Line"
0 GDUs remaining to maturity
Yield loss = 0%
Lodging – Few objects in nature can resist flowing water, including corn roots and stalks. Lodging may be evident immediately when flood waters recede, or it may occur later as weakened roots or stalks eventually succumb to fall wind and weather events. Diseases may be transmitted to roots and stalks during even moderate flooding. In addition, lodging places the ear near ground level where it may be submerged and subject to deterioration of grain quality. Where flooding results in lodging, fields should be monitored closely and harvested as soon as practical.
Grain Quality – If ears are submerged by flood waters, grain quality will likely be the primary concern for growers. In addition to period of submersion, corn stage of maturity and weather conditions following flooding determine effect on grain quality. If corn that has reached maturity is soaked by flood waters or constant rainfall, "premature sprouting" or "vivipary" of kernels may result (Figure 2).
Scouting fields and scheduling harvest based on crop condition as well as grain moisture are essential in flooded fields. Harvesting some fields early, at grain moistures near 25%, may be necessary to prevent further deterioration of grain quality. On other fields that have retained root, stalk and grain quality, compaction can be prevented by harvesting later, allowing fields to adequately dry.
When grain quality is low, adjust combine settings to minimize trash and broken kernels. Check with the combine manufacturer for machine-specific recommendations. (Combine mechanics or other dealership staff are often a good source for this information.)
Proper storing, drying and maintaining grain quality will minimize problems of flood damaged and sprouted grain.