Adding insult to injury in this much delayed 2019 planting season, a series of heavy rainfall events have left those fields that did get planted with water logged, saturated soils.  In some fields, there is standing water (ponding) or flooded conditions that have completely submerged young corn plants.  Although no one can state with absolute certainty what the long-term consequences to the crop are due to these conditions, there are factors that influence the degree of damage.  I’m going to pull information from a May 2019 Purdue newsletter article written by Bob Nielsen, Extension corn specialist and from May 2018 and June 2019 OSU Extension CORN newsletter articles by Extension specialists Peter Thomison, Steve Culman and Alex Lindsay regarding those damage risk factors.

Completely submerged plants are at higher risk for injury or death as compared to partially submerged plants.  In addition, the longer an area remains ponded the higher the risk for plant death because soil oxygen is depleted within about 48 hours of soil saturation.  According to the Purdue article, current thinking is young corn can survive up to about 4 days of outright ponding if temperatures are relatively cool (mid-70's F or cooler); fewer days if temperatures are warm (mid-70's F or warmer).  In terms of corn development, corn younger than stage V-6 is more susceptible to ponding damage than corn older than V-6.  One reason is simply that V-6 corn is taller and less likely to be fully submerged.  Perhaps more significantly, corns growing point remains below the soil surface until about the V-6 growth stage.  Damage to the growing point directly affects the plant’s ability to survive.  Split stalks and make a visual examination of the lower stem to assess growing point health.  It should be white to cream in color.  If the growing point is healthy, new leaves should emerge from the corn whorl within three to five days after water has drained away.

There is a relationship between ponding, nitrogen loss, post ponding nitrogen application and yield.  From the OSU Extension CORN newsletter articles; “In Ohio in 2017-2018, we observed a 10% yield loss when corn was flooded at V4 for 2 days and received 120 lbs. N pre-plant + 60 lbs. N sidedress (applied post-flood). When flooded for 4 or 6 days, yield loss increased to 15 and 33%, respectively, when receiving the same N regime. If the additional 60 lbs. N was not side-dressed post-flood, yield losses increased to 30, 50, or 57% for 2, 4, or 6 days of flooding, respectively.”

Some other ponding/flooding impacts described in those CORN newsletter articles include disease problems with corn smut and crazy top, although the economic impact is usually negligible.  Bacteria deposited in leaf whorls by flooding can also result in disease and kill plants.

Rory Lewandowski is an OSU Extension Agriculture & Natural Resources Educator and may be reached at 330-264-8722.

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