Considerations for corn planted under wet conditions
Recent rains have created very wet soil conditions in parts of Kansas. Some corn remains to be planted. What should producers expect if they plant corn into soils that are too wet, and what can they do to minimize any problems?
It is best, of course, to allow time for the soil to dry adequately before tillage or planting operations if at all possible. Wet conditions will make the soil more susceptible to compaction. Tilling some soils when they are too wet can produce large, persistent clods, complicate planting, reduce herbicide effectiveness, and destroy the seedbed. Also, compaction can occur in the seed furrow itself, restricting proper root development (also diminishing nutrient accessibility) and early plant growth.
If soils remain or become unusually wet after the corn has emerged, corn may look sickly for a while. Saturated soils inhibit root growth, leaf area expansion, and photosynthesis because of the lack of oxygen and cooler soil temperatures. Yellow leaves indicate a slowing of photosynthesis and plant growth. Leaves and sheaths may turn purple from accumulation of sugars if photosynthesis continues but growth is slowed.
Corn plants can recover with minimal impact on yield if the plants stay alive and conditions return to normal fairly quickly (early during the growth period). Although root growth can compensate to some extent later in the season, a saturated profile early in the season can confine the root system to the top several inches of soil, setting up problems later in the season if the root system is inadequate to extract needed water from lower in the profile.
If weather conditions persist for more than a week, corn emergence will be delayed and seedling will be more vulnerable to the presence of insects and diseases. Uneven corn stands likely will be greater when planting in cold and wet soils. This situation will be directly affecting the plant-to-plant uniformity, which could have an impact on the potential yield.
Figure 1. Uneven corn stand due to cold, wet weather in late April. Photo by Ignacio Ciampitti, K-State Research and Extension.
Saturated soils can also cause loss of nitrogen fertilizer by either denitrification (loss of nitrogen to the atmosphere) or leaching (movement of nitrogen beyond the rooting zone). For denitrification to occur, the soil doesn’t need to be completely saturated. Denitrification can also occur at 85-90% of the pore space filled with water. Nitrogen in the nitrate (NO3) form is needed for these losses to occur. Therefore a combination of fertilizer source, application time and the use of nitrification inhibitors can reduce leaching and denitrification.
Corn may respond to in-season nitrogen applications if a large portion of early-applied nitrogen is lost to these processes. Keep an eye out for nitrogen deficiency symptoms on fields that have been saturated for long periods. It may not be a bad idea to apply a strip or two of a high rate of nitrogen in those fields as soon as possible to serve as a fully-fertilized reference point.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Stu Duncan, Northeast Area Crops and Soils Specialist
Doug Shoup, Southeast Area Crops and Soils Specialist
Dorivar Ruiz Diaz, Nutrient Management Specialist
DeAnn Presley, Soil Management Specialist