Waterlogging and flooding are among the most damaging weather-related stresses in crop production worldwide, and their impacts are increasing as extreme rainfall becomes more frequent. Flooding ranks second only to drought among environmental, non-living stresses.
When heavy rains leave water standing in fields, the excess moisture suffocates plant roots by pushing essential oxygen out of the soil. According to research by University of Missouri Extension soil scientist Gurbir Singh and MU assistant research professor Gurpreet Kaur, this lack of air disrupts growth and can severely reduce yields.
Flooding submerges plants, while waterlogging fills soil pores with water. Both limit oxygen in the root zone, disrupting growth and reducing yields. Survival depends on seed quality, flood duration, water temperature, drying speed and growing-point location.
In Missouri’s claypan or floodplain soils, even short saturation can cause nitrogen loss, reduce root growth and lower plant vigor because of slow drainage, plant roots need air exchange, says Singh.
Timing, crop, duration matter
Plants are most vulnerable when they are young and have shallow roots and limited energy reserves. Warm temperatures intensify stress and plant diseases.
Corn plants can suffer oxygen deprivation within just 24 to 48 hours of flooding. This stunts root growth and prevents the plant from absorbing nutrients. Prolonged flooding can permanently cut corn yield potential by 7% to 20%.
While soybeans can survive short periods of wet soil early on, prolonged flooding can be devastating. Sitting in early-season floods can cost farmers 1 to 3 bushels per acre for every day the water remains, largely because the water kills off thousands of plants.Early growth stages are most vulnerable because of shallow roots and limited energy reserves.
Nitrogen loss is key
Washed-away nutrients
Waterlogged soils quickly wash away essential nutrients like nitrogen.
Singh notes that farmers who apply all of their nitrogen fertilizer at once early in the season face a higher risk of losing that investment in a flood. Breaking fertilizer into multiple, smaller applications can help reduce this loss.
If early fertilizer is washed away, all is not lost. MU Extension agronomist Kelly Nelson says applying "rescue" nitrogen later in the season can still help corn recover, though it may not completely restore the crop's original yield potential.
Consider replant decisions
If extended flooding kills plants and reduces soybean population, it is time to consider replanting, says MU Extension specialist Andre Reis.
Reis advises farmers not to focus solely on the number of surviving plants. Often, a field with fewer plants that are evenly spaced will produce a better yield than a heavily populated but patchy field. Farmers must weigh the cost of replanting against the reality that crops planted later in the summer naturally produce lower yields.
Furthermore, crops that survive early floods may struggle later if the summer turns dry, because the floodwaters likely stunted their early root development.
He advises scouting fields and using the 2025 MU Extension replant worksheet and guide, which outlines seven steps to consider: determine cause, assess stand, estimate yield and revenue (current vs. replant), calculate replant cost and decide cost-effectiveness.
Scout fields for disease
Watch for diseases favored by wet conditions, says Peng Tian, director of the MU Plant Diagnostic Clinic.
Standing water creates a perfect breeding ground for diseases. MU Plant Diagnostic Clinic Director Peng Tian and plant pathologist Mandy Bish warn that wet conditions increase the risk of fungal infections and root rot in young soybeans, as well as head blight in wheat.Weed management issues follow
Finally, flooding disrupts standard weed control. MU Extension weed scientist Kevin Bradley notes that standing water and mud can wash away early herbicides and prevent farmers from getting equipment into the fields to manage new weed growth.
You can read the entire journal article on waterlogged or flooded soils at https://doi.org/10.1002/agj2.20093.
CUTLINE
A study of northeastern Missouri soils shows a direct link between how long a cornfield remains flooded and its eventual yield. As demonstrated in this data from 2013 and 2014, every additional day of standing water steadily decreases the number of bushels harvested per acre.
COURTESY / AGRONOMY JOURNAL
