Dr. Dan Talks Agronomy

Parts of northeast Nebraska were hit by a heavy storm early June 18. At our farm we picked up 2 inches of rain with winds out of the northeast at 30-plus miles per hour and wind gusts of 50-plus mph. (This information came from the DTN weather station at the farm.) However, further south in Dodge County, winds were weaker but the rain was heavier, 5 to 6 inches; flooding even closed a local highway.

I drove through northern Dodge County to assess crop damage. Much of the corn was leaning 30 to 60 degrees, especially on the leading edge of the field. In the bottoms, corn was often flattened by flood water and covered by crop residue. Fortunately, soybeans weathered the storm well because they were only a few inches tall.

Was the damage I saw green snap or something else? What is the likelihood this corn will recover?

Green snap is breakage of the stalk by high winds. This weather-related event occurs primarily in the central and Western Corn Belt when corn is relatively small, from V5 to V8, and then when it is growing rapidly, from V12 to VT (tassel).

During these two periods, corn is adding new cells and cells are expanding, but cell walls can still lack some structural integrity. In northeast Nebraska, the week prior to the storm was hot with daytime air temperatures in the 90s. Everyone was commenting how fast corn was growing and how green it was. This period of rapid growth, like the bean stalk in the Jack and the Beanstalk fairy tale, set up the potential of green snap.

Many factors can influence green snap vulnerability, including post herbicides, periods of hot weather and rapid growth, storms with high winds and large amounts of rain, high rates of nitrogen, hybrid vulnerability, shallow seeding, small or weak root systems, etc. Even strong hybrids can be vulnerable to green snap if they are growing rapidly with a lot of inputs applied and a storm with high winds occurs. Shallow seeding raises snap risk by reducing root development.

But usually it is just high winds.

True green snap is when the plant's stem is bent over and broken -- or snapped over -- but not broken completely off. The structural integrity has been compromised, which includes the vascular tissue, xylem that moves water and nutrients up and phloem that moves sugars down. Once the vascular tissue is compromised at the snap point, it is highly unlikely the plants will recover.

Plants that are just pushed over from the wind and partially dislodged from the soil are lodged. Plants at V5 to V6, like I saw in the field after the storm, may recover as some will re-erect themselves naturally. Others that were pushed over more fully, will begin to regrow upright, creating that jointed goose-neck appearance.

Growers have to wait several days to see how the plants recover. If it is true green snap, and I am sure some of it was, those plants will be lost and this will affect yield. However, if the plants are only root-lodged at this point or just pushed over, they will likely recover. Dr. Bob Nielsen at Purdue wrote a review on the impact of winds on corn and it is posted here: https://www.agry.purdue.edu/…

Dan Davidson can be reached at AskDr.Dan@dtn.com

(CZ/BAS)

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