Field Flooding & Its Effects

Last week’s heavy rains in parts of the county reminded me of an article I read last year about the survivable chances for corn that has been flooded in low-lying areas so I’ve summarized and put some excerpts from an article written by R.L. Bob Nielsen from the Purdue University, Agronomy Department. Obviously, plants that are completely submerged are at higher risk than those that are partially submerged and the longer an area remains ponded, the higher the risk of plant death.

Wind damge overturned many pivots in Fillmore County and excessive rain caused some flooding.
Wind damge overturned many pivots in Fillmore County and excessive rain caused flooding.

Nielsen reported that most agronomists believe that young corn can survive up to about 4 days of outright ponding if temperatures are relatively cool (mid-60’s F or cooler); fewer days if temperatures are warm (mid-70’s F or warmer). Soil oxygen is depleted within about 48 hours of soil saturation. Without oxygen, the plants cannot perform critical life sustaining functions; e.g. nutrient and water uptake is impaired and root growth is inhibited. Even if surface water subsides quickly, the likelihood of dense surface crusts forming as the soil dries increases the risk of emergence failure for recently planted crops.

Young corn (less than V-6 stage, like our current conditions) is more susceptible to ponding damage than corn beyond the sixth leaf stage. This is because young plants are more easily submerged than older and taller plants and since the corn plant’s growing point remains below ground until about V6. The health of the growing point can be assessed initially by splitting stalks and visually examining the lower portion of the stem. Within 3 to 5 days after water drains from the ponded area, look for the appearance of fresh leaves from the whorls of the plants.

Another consideration is that extended periods of saturated soils AFTER the surface water subsides can also take their toll on the overall vigor of the crop, causing stunted roots and dying roots. As a result, plants may be subject to greater injury during a subsequently dry summer due to their restricted root systems.

Loss of nutrients is another concern on saturated soils. Significant loss of soil N will cause nitrogen deficiencies and possible additional yield loss.  Lengthy periods of wet soil conditions also favor the development of seedling blight diseases, especially those caused by Pythium fungi.  Poorly drained areas of fields are most at risk for the development of these diseases and will also be risky for potential replant operations.

There are other diseases that can affect flooded areas of corn as well, but for now, it’s kind of a wait and see until you can get into the field and assess the health of the growing point. More information from Effects of Flooding or Ponding on Young Corn by R.L. Nielsen.

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