Recent intense rainfall events (technically referred to as “toad stranglers” or “goose drownders”) have caused flooding of low-lying corn fields or ponding (standing water) in poorly drained swales within fields. Other areas within fields, while not technically flooded or ponded, may remain saturated for lengthy periods of time.

What are the prospects for recently submerged corn fields or plants simply enduring days and days of saturated soils? The flippant answer is that such suffering crops will survive until they die.

What I mean to say is that no one can tell you with certainty the day after the storm whether a ponded area of a corn field will survive or whether there will be long-term yield consequences until enough time has gone by such that you can assess the actual recovery of the damaged plants. We can, however, talk about the factors that increase or decrease the risks of severe damage or death to flooded soils.

  • Plants that are completely submerged are at higher risk than those that are partially submerged.
    • Plants that are only partially submerged may continue to photosynthesize, albeit at limited rates.
  • The longer an area remains ponded, the higher the risk of plant death.
  • 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 (Wiebold, 2013).
  • Be prepared with a rotary hoe to break up the crust and aid emergence.
  • Ironically, such situations would benefit from another rainfall event to wash the mud deposits from the leaves.
  • 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.
  • This is partly because young plants are more easily submerged than older taller plants and partly because 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 (Nielsen, 2008a). 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.
  • Some root death will occur and new root growth will be stunted until the soil dries to acceptable moisture contents. As a result, plants may be subject to greater injury during a subsequently dry summer due to their restricted root systems.
  • Nutrients like nitrogen are rapidly remobilized from lower leaves to upper, newer leaves; resulting in a rapid development of orange or yellow lower leaves.
  • Because root function in saturated soils deteriorates, less photosynthate is utilized by the root system and more accumulates in the upper plant parts. The higher concentration of photosynthate in the stems and leaves often results in dramatic purpling of those above-ground plant parts (Nielsen, 2012).
  • Damage to the root system today will predispose the crop to the development of root and stalk rots later by virtue of the photosynthetic stress imposed by the limited root system during the important grain filling period following pollination. Monitor affected fields later in August and early September for the possible development of stalk rots and modify harvest-timing strategies accordingly.
  • Significant loss of soil N will cause nitrogen deficiencies and possible additional yield loss.
  • On the other hand, if the corn dies in the ponded areas it probably does not matter how much nitrogen you've lost.
  • Poorly drained areas of fields are most at risk for the development of these diseases and so will also be risky for potential replant operations.
  • The fungus that causes crazy top depends on saturated soil conditions to infect corn seedlings.
  • The common smut fungal organism is ubiquitous in soils and can infect young corn plants through tissue damaged by floodwaters. There is limited hybrid resistance to either of these two diseases and predicting damage is difficult until later in the growing season.
  • The greater the deposition of mud or old crop residues on plants as the water subsides, the greater the stress on the plants due to reduced photosynthesis.
  • Mud and crud that cakes the leaves and stalks encourage subsequent development of fungal and bacterial diseases in damaged plant tissue. In particular, bacterial ear rot can develop when flood waters rise up to or above the developing ears of corn plants (Nielsen, 2003).
  • Corn younger than about V6 (six fully exposed leaf collars) is more susceptible to ponding damage than is corn older than V6.
  • Extended periods of saturated soils AFTER the surface water subsides will take their toll on the overall vigor of the crop.
  • Concomitant (I found a new word in the dictionary!) with the direct stress of saturated soils on a corn crop, flooding and ponding can cause significant losses of soil nitrogen due to denitrification and leaching of nitrate N.
  • Lengthy periods of wet soil conditions favor the development of seedling blight diseases in young corn seedlings, especially those caused by Pythium fungi (Sweets, 2014).
  • Certain diseases, such as common smut and crazy top, may also become greater risks due to flooding and cool temperatures (Pataky and Snetselaar, 2006; Jackson-Ziems, 2014, APS, 2015).
  • Wind damage to corn occurs either as stalk breakage (aka “green snap”) or root lodging (plants uprooted and laying nearly flat to the ground). The yield effect of “green snap” damage depends on the percentage of field affected and whether the stalk breakage occurs above or below the ear, but is usually serious regardless. Obviously, stalk breakage below the ear results in zero yield for that plant. Stalk breakage above the ear results in significant yield loss due to the loss of upper canopy photosynthesis capacity for that plant. Root lodged corn will recover or straighten up to varying degrees depending on the growth stage of the crop. Generally, younger corn has a greater ability to straighten up with minimal “goose-necking” than older corn. Yield effects of root lodging depend on whether soil moisture remains adequate for root regeneration, the severity of root damage due to the uprooting nature of root lodging, and the degree of “goose-necking” that develops and its effect on the harvestability of the crop.

Related References

APS. 2015. Crazy top on corn. American Phytopathological Society. http://www.apsnet.org/publications/imageresources/Pages/Iw000015.aspx [URL accessed June 2015].

Butzen, Steve. Flooding Impact on Crops. Pioneer Hi-Bred Int'l. Online at http://www.pioneer.com/home/site/us/template.CONTENT/agronomy/crop-management/adverse-weather-disease/flood-damage/guid.DE1A9B1D-CAC0-4A04-B9CC-E0820B29080A [URL accessed June 2015].

Ciampiatti, Ignacio, Kraig Roozeboom, and Doug Jardine. 2014. Effect of water-logged soils on corn growth and yield. eUpdate, Kansas State Univ. [On-line] Available at https://webapp.agron.ksu.edu/agr_social/eu_article.throck?article_id=255 [URL accessed June 2015].

Coulter, Jeff, Seth Naeve, Dean Malvick, and Fabian Fernandez. 2014. Considerations for Flooded Corn and Soybean. Minnesota Crop News, Univ of Minnesota Extension. http://blog-crop-news.extension.umn.edu/2014/06/considerations-for-flooded-corn-and.html [URL accessed June 2015].

Elmore, Roger and Lori Abendroth. 2008. Flooded Corn and Saturated Soils. Integrated Crop Management Newsletter, Iowa State Univ Extension. Online at http://www.extension.iastate.edu/CropNews/2008/0530RogerElmoreLori+Abendroth.htm [URL accessed June 2014].

Farnham, Dale. 1999. Corn survival in wet conditions. Iowa State Univ. Integrated Crop Management Newsletter. [On-line] Available at http://www.ent.iastate.edu/ipm/icm/1999/5-24-1999/wetcorn.html [URL accessed June 2014].

Jackson-Ziems, Tamra. 2014. Corn Diseases: Crazy Top . CropWatch, Univ. of Nebraska Extension. Video at https://youtu.be/1QSTWMEKreM [URL accessed June 2015].

Laboski, Carrie. 2013. Potential for Nitrogen Loss Following Heavy Rainfalls. NPK et cetera. Univ of Wisconsin Extension. http://www.npketc.info/?p=180 [URL accessed June 2014].

Malvick, Dean. 2014. Soybean and Corn Seedling Diseases Increase With Flooded and Wet Soil Conditions. Minnesota Crop News, Univ of Minnesota Extension. http://blog-crop-news.extension.umn.edu/2014/06/soybean-and-corn-seedling-diseases.html [URL accessed June 2015].

Nielsen, R.L. (Bob). 2003. Bacterial Ear Rot in Corn Due to Flooding. Corny News Network, Purdue Univ. [online] http://www.kingcorn.org/news/articles.03/EarRot-0720.html. [URL accessed June 2015].

Nielsen, RL (Bob). 2008a. Growing Points of Interest. Corny News Network, Purdue Univ. Online at http://www.kingcorn.org/news/timeless/GrowingPoints.html [URL accessed June 2015].

Nielsen, RL (Bob). 2008b. Tips for Staging Corn with Severe Leaf Damage. Corny News Network, Purdue Univ. Online at http://www.kingcorn.org/news/timeless/VStagingTips.html. [URL accessed June 2015].

Nielsen, RL (Bob). 2012. Prevalent Purple Plants Perennially Puzzle Producers. Corny News Network, Purdue Extension. Online at http://www.kingcorn.org/news/timeless/PurpleCorn.html [URL accessed June 2015].

Nielsen, RL (Bob). 2014a. Determining Corn Leaf Stages. Corny News Network, Purdue Univ. Online at http://www.kingcorn.org/news/timeless/VStageMethods.html [URL accessed June 2015].

Nielsen, RL (Bob). 2014b. Use Thermal Time to Predict Leaf Stage Development in Corn. Corny News Network, Purdue Univ. Online at http://www.kingcorn.org/news/timeless/VStagePrediction.html [URL accessed June 2015].

Pataky, J. K., and K. M. Snetselaar. 2006. Common smut of corn. The Plant Health Instructor. DOI:10.1094/PHI-I-2006-0927-01 [On-line] Available at http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/CornSmut.aspx [URL accessed June 2015].

Sweets, Laura. 2014. Seed Decay and Seedling Blights of Corn. Integrated Pest & Crop Management Newsletter, Univ of Missouri Extension. Online at http://ipm.missouri.edu/IPCM/2014/4/Seed-Decay-and-Seedling-Blights-of-Corn/ [URL accessed June 2014].

Thomison, Peter. 2010. Ponding Effects on Corn. C.O.R.N. Newsletter, Ohio State Extension. Online at http://corn.osu.edu/newsletters/2015/2015-15/ponding-effects-on-corn [URL accessed June 2015].

Wiebold, Bill. 2013. Heavy Rains Exclude Oxygen Needed for Seedling Health from Soils. Integrated Pest & Crop Mgmt, Univ of Missouri. Online at http://ipm.missouri.edu/IPCM/2013/5/Heavy-Rains-Exclude-Oxygen-Needed-for-Seedling-Health-from-Soils [URL accessed June 2014].