Saturated soils have many farmers in eastern and central Kansas worried about corn planting, says Kraig Roozeboom, K-State Research and Extension crop production specialist. But that's not the only potential problem. There is also concern about the effect of flooding and saturated soil conditions on corn already in the ground, he said.
"The recent heavy rains have subjected much of the corn that has been planted to saturated soils or flooding. Early-season flooding can cause immediate problems for small corn plants and can have season-long implications as well," Roozeboom says.
Saturated soils inhibit root growth, leaf area expansion, and photosynthesis because of the lack of oxygen and cooler soil temperatures, he explains.
"Yellow leaves indicate that photosynthesis and plant growth have slowed. Leaves and sheaths may turn purple from accumulation of sugars if photosynthesis continues, but growth is slowed," the agronomist says.
"Corn plants can recover with minimal impact on yield if the plants stay alive and conditions return to normal fairly quickly. Waterlogging early in the season can confine the root system to the top several inches of soil. Although root growth can compensate to some extent later in the season, this can set up problems later in the season if the root system is inadequate to extract needed water from lower in the profile," he says.
Young corn plants can tolerate only a few days of full submersion.
"Before the six-leaf stage of growth, when the growing point is at or below the soil surface, corn can survive only two to four days of flooding. Once the water recedes, producers should examine the growing point to determine if plants are still viable. A healthy growing point should be white or cream colored. If the growing point turns grey or brown and begins to soften, the plant likely will not survive," Roozeboom explains.
The Chances of plant survival increase dramatically if the growing point is not completely submerged, or if it is submerged for less than 48 hours, he said.
Research has demonstrated yield reductions from early-season flooding ranging from 5 to 32%, depending on soil nitrogen status and duration of flooding.
Temperatures can influence the extent of damage from flooding or saturated soils, he says. Cool, cloudy weather limits damage from flooding because growth is slowed and because cool water contains more oxygen than does warm water.
However, these conditions can result in more soil disease problems, he notes.
If corn has not yet been planted, or if a field must be replanted, allow time for the soil to dry adequately before tillage or planting operations, adds Randy Price, K-State Research and Extension biological and agricultural engineer.
"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," Price says. "Also, compaction can occur in the seed furrow itself, restricting proper root development and early plant growth."
If producers have to get into a field, a good guidance system can allow them to plant higher elevations first and then return to lower elevations later in the day after areas have had more time to dry, he adds.