Managing Crops Damaged by Mid-to-late Season Flooding

By Daniela Carrijo and Paul D. Esker et.al

Flooding (i.e., partial or complete submergence) events occurring in the mid-to-late growing season can result in significant yield and crop quality losses. Plant death of soybeans and corn typically does not occur if the soil is drained within 96 hours of the flooding event. However, the biggest concerns with flooding mid-late season are: 1) significant lodging preventing the crop from being harvested and 2) crop quality issues such as soil deposition on the grain, sprouting, and mycotoxin contamination. Soybeans are typically more affected than corn because they are more susceptible to lodging and the lower pods are easily exposed to flood waters. If damage is significant, make sure to document everything with pictures, and contact the crop insurance adjuster and the local FSA office to report losses. According to the Food and Drug Administration (FDA), food crops exposed to flood waters are considered adulterated and should not enter the food or feed supply through commercial facilities. For feed crops, it is suggested that affected crops be tested for mycotoxins, heavy metals, pathogenic bacteria, and pesticides.

Below are some farm-level recommendations for managing crops partially or wholly submerged mid-to-late season.

Corn for Silage

• Corn destined for silage will be more at risk for fungal and bacterial contamination. Take steps to promote good fermentation, such as heavy inoculation and extra packing in the silos. A good fermentation will kill many (but not necessarily all) pathogens in the silage.
• Target the least affected fields for silage and harvest above the silt line to avoid soil contamination.
• Avoid chopping corn for silage that has considerable dirt or silt on it.
• Segregate any corn chopped for silage to be evaluated before feeding. Forage should be tested before feeding, paying particular attention to dry matter percent, starch, ash, mycotoxins, and fermentation profile.
• Silage and high moisture corn from these fields should be evaluated at feed-out and animal health should be closely monitored. Soil contamination alone may not be a serious animal health factor. Still, contamination from manure, sewage treatment plants, and other chemicals is unknown and could vary from one situation to another.
• In all cases, try to minimize the soil contamination and during feed-out, attempt to dilute these forages with normal quality forages as much as possible.

Corn for Grain

• Harvesting for grain is likely a better option than for silage when flooding has occurred.
• Combine air filters will likely need to be changed more frequently, and operators should take steps to avoid breathing the dust.
• Harvest when the fodder is dry to help limit the soil in the grain. Monitor the soil in the corn coming into the bin and avoid the worst sections of fields.
• Harvesting high-moisture corn at the drier range of acceptable levels could improve the ability to clean soil from the corn.
• The expected quality of grain is uncertain and should be monitored. The potential for crop contamination by flood waters could affect the marketability of grain and silage. Check with grain brokers for more information on marketability as it becomes available.
• Monitor for sprouting. Some river bottom fields are prone to bird damage and often have some sprouting risk. The flood may exacerbate the problem. Try to adjust the combine to remove most of the sprouted grain.
• Monitor for molds. Corn from flood-damaged fields should be evaluated for grain quality and kept separate if there are indications of molds. Mold and mycotoxin levels can be determined by most feed testing laboratories and used as guidance in marketing.
• The risk of molds and sprouting is likely a function of the exposure to the water and stage of growth. Corn under water will have an increased risk of molds and bacterial rotting. This may be more pronounced in corn already drying down (less than 40% grain moisture) and then taking on moisture during the flood.
• Monitor for stalk rots. Fields that remained flooded for over 12 hours are most at risk for stalk rots.
• The crop may mature more rapidly under these conditions since corn that has been stressed when near maturity often seems to dry down fast.
• If the grain is deemed unfit for animal use, it will be necessary to pursue crop insurance claims. If producers expect a claim, they should consult with an adjuster prior to harvest.

Hay and Pasture Crops

• Soil and organic matter on forage crops can also lead to fermentation issues, increased ash, decreased digestibility, and animal health problems, especially for horses.
• Avoid pasturing or harvesting silt-laden forage crops if possible.
• If pastures are grazed, don't allow the animals to graze the plants too close to the ground. The majority of the contamination will be in that area of the plant.
• It might be best to mow the previously flooded pastures and wait for them to regrow before grazing.
• Mowed forage that has been lying in the field for more than one week should be chopped and blown back onto the field, particularly if it is showing signs of molding (forage is slimy).
• Roots in soil flooded for 2 to 3 weeks may die from suffocation (no oxygen available for the roots to respire).
• Root diseases such as Rhizoctonia or Phyotphtora can increase in wet soils and lead to thinned stands next year.
• Avoid pasturing or harvesting silt-laden forage crops if possible.

Soybeans

• Monitor grain quality prior to harvest. Soybean crops are likely to experience increased harvest losses and machinery problems during harvest. Many soybeans may be impossible to harvest due to lodging and debris.
• Harvest and, if possible, store soybeans from flooded areas separately from areas that were not flooded.
• Monitor grain moisture. Due to stress-induced senescence, flooded soybeans may mature earlier than non-flooded ones.