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Flooding, Ponding, and Corn Damage

June 15, 2020

Iowa has experienced periods of flooding and ponding as a result of recent rains.  Smith Fertilizer and Grain agronomists have been scouting fields and evaluating damage.  The extent to which flooding injures corn is determined by several factors including the plant stage of development when flooding occurs, the duration of flooding, and the air and soil temperatures.

Prior to V6, the 6th collar, or when the growing point is near or below the surface, corn can survive only two to four days of flooded conditions.  The oxygen supply in the soil is depleted after about 48 hours in a flooded field.  Without oxygen, the plant cannot perform critical life sustaining functions; nutrient and water uptake is impaired, root development is inhibited.

If temperatures are warm during flooding, greater than 77 degrees, plants may not survive 24 hours. Cooler temperatures prolong survival.  Once the growing point is above the water level the likelihood for survival improves greatly.  Since most of the corn in Iowa has not yet reached the 6th collar stage, there is potential for flooding and ponding injury.

Even if flooding doesn’t kill plants outright it may have a long term negative impact on crop performance.  Excess moisture during the early vegetative stages retards corn root development.  As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water.  Flooding and ponding can also result in losses of nitrogen through denitrification and leaching.

If flooding in corn is less than 48 hours, crop injury should be limited.  To confirm plant survival, have your Smith Fertilizer and Grain agronomist check the color of the growing point, it should be white and cream colored, while a darkening or softening usually precedes plant death.  Also look for new leaf growth 3 to 5 days after water drains from the field.

Cooler, wet weather conditions also favor development of seed rots and seedling blights.  Seed treatments are usually effective but can provide protection only so long; if seedling development is slowed or delayed 2 or 3 weeks, soil borne pathogens have a much greater opportunity to cause damage.  Other disease problems which may become greater risks due to flooding and cool temperatures are corn smut and crazy top.  The fungus that causes crazy top depends on saturated soil conditions to infect corn seedlings.  There is limited hybrid resistance to these diseases and predicting damage is difficult because disease symptoms do not appear until later in the growing season.

Replanting decisions due to flooding and ponding damage are never easy and should always be carefully evaluated.  The first thing you need to do with these fields is to evaluate them after the crop has a chance to recover, typically 5 to 7 days before making any decisions to replant. 

Excessive floods and ponding can lead to loss of needed plant nutrients that were applied.  Have your Smith Fertilizer and Grain agronomist explain how Nutri Scription can help replace these vital nutrients that have been lost.
Posted: 6/15/2020 2:15:24 PM by Rob Matherly | with 0 comments

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