Historical archive Covering the May 12, 2000 "St. Nazianz Storm" and Recovery  

Agronomy- Hail as of 5/15/00

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Crop Management Decisions Following Hail Damage 
(S.R. Hendrickson, Agricultural Agent, UW Extension, 5/15/00)

Recent hail damage presents a variety of crop management concerns for local growers and crop management professionals.  Beyond this article, further information is available at http://www.uwex.edu/ces/cty/manitowoc/agcropprod.html


Prior to, and for some time after emergence, the corn plant is affected very little by hail damage. At emergence, the plantís growing point is below the soil surface and remains there for about 3 weeks (until five to seven leaves have fully emerged). Because the growing point is below the soil surface and in the leaf whorl, plant damage to hail at these early stages rarely results in any significant stand or yield loss. Approximately 3 weeks after emergence, all nodes and internodes have developed, and the growing point is elevated above the soil surface. Most corn at the point of the hail storm on 5/12/00 had not developed five to seven fully emerged leaves and should developed normally. The exception would be in situations of severe erosion where seed may have washed away.

Alfalfa/Red Clover

Most alfalfa was ready for harvesting at the time of the hail storm. Both yield and quality will be affected. Where terminal (highest) portions of the plant have been damaged, stem growth stops. Forage quality losses also occur since the top and quality portions of the plant are removed when hail defoliates the plant. In some cases, alfalfa plants have been severed to ground level. Where stands are uneven and partially damaged, harvesting the week of 5/15/2000 or as soon as practical is recommended. New stem growth for a second crop will emerge from the crown at the base of the plant.

Second crop growth of course will take 25-30 days. Where stands have been completely severed and there isnít any matting over the crowns, there is little to be gained from making a harvesting pass over the field. Where there is substantial tissue matting over the crowns, harvesting is recommended to allow for unimpeded re-growth from the crown at the base of the plant. Re-growth should be monitored as an assessment of potential crown damage. New alfalfa seedings may or may not have emerged at the time of the storm. These fields should be watched for at least a week to 10 days to assess damage and emergence. As a rough thumb rule for new seedings and established stands, one needs at least half a stand to warrant keeping.

When harvesting lodged alfalfa red clover or red clover, disc mowers will pick up more forage than sickle bar mowers. Harvesting against the direction the forage is leaning will allow more to be harvested. With both mower types, tilt the cutter bar or discs forward to increase forage pick up. When using a sicklebar mower one can additionally move the reel forward and down and increase reel speed to help pick up downed forage. For most growers, using equipment that is already on the farm is the most practical approach.


Soybean plants for the most part were just emerging at the time of the storm. Cotyledons (the first two leaves that push through the ground) may or may not have been up. Plants that are severed below the cotyledons will not recover. The cotyledon tissue provides the supply of energy needed for re-growth. Plants severed above the cotyledons will likely recover if the axillary buds are in tact. These buds are just above the cotyledons. Soybeans have significant capacity to yield with reduced stand counts. As an example, if a stand at 200,000 plants per acre is predicted to yield 100% of potential, a stand of 120,000 plants per acre is predicted to yield 93% of its potential. These figures apply to plantings between May 1 and May 20th.  UW Extension offices have a fact sheets available to monitor stand counts and make replant decisions.


Winter wheat was fast approaching the flag leaf stage (the last emerging leaf that largely determines yield). Where stems were severed below this point, damage would be substantial. Where damage is severe, corn or soybeans can be replanted in timely fashion. Re-growth from wheat stubble is insignificant.

Crop Insurance

A reminder as well to check with your insurance adjuster on crop damage. Be sure to leave a portion of a damaged stand for inspection if requested.



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