Effects of flooding and saturated soils on corn
Nitrogen is lost to leaching when in the nitrate form. Since we have seen some warm temperatures this spring it is likely a lot of nitrogen applied in the ammonium form has been converted to nitrate making it more susceptible to loss. Nitrogen loss will likely be more severe in low areas of the field where ponding occurs and more water is moving through the soil profile. If field conditions permit, a supplemental N application may be needed to ensure the corn crop has enough N to reach its full yield potential.
Assessment and Management
It is best to wait about five days after a flooding event to fully assess your crop. It is likely no field work can be done in this period, and it will allow corn plants time to show signs of recovery. Examine the growing point by splitting the seedlings lengthwise. If you see signs of a healthy growing point and the appearance of fresh leaves from the whorl then the plant may be able to recover a lot of its yield potential. Young corn plants can only tolerate a few days of full submersion, especially with warm temperatures. Corn can recover with minimal impact on yield potential if the plants stay healthy and favorable growing conditions occur.
After enough time has passed, you can properly assess the health of corn plants with a stand evaluation. This tells you whether replant action is necessary. As with any replant situation, it is best to use a formula that takes into account targeted stand, actual stand and possible replant date to evaluate whether replanting would in fact be more profitable than leaving the current stand. Using a replant worksheet or formula will help you to make a management decision based on economics and not on emotion. Many university extension services have a replant decision tool available for use. You can find the replant checklist from Iowa State here: http://www.agronext.iastate.edu/corn/production/management/planting/replanting.html.
A Silver Lining
One good thing that can come from saturated soils during late May and early June is its effect on rootworm larvae survival. One of the few weak points in corn rootworms’ life cycle is the period when larvae are hatching from eggs. In order for rootworm larvae survival to be affected, soils must be saturated long enough to suffocate larvae as they are hatching and in the early part of their life cycle.