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 plant’s 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.
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 isn’t 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.
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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