Owner`s manual

Salvaging Crops After Flooding
RECOVERY OF ALFALFA, IRRIGATED PASTURES AND HAY
Many factors affect the extent of
crop damage after a flood.
Seasonal temperatures can be a
major factor. A July flood, for
example, is often much worse
for crop survival than a spring
flood. The warmer mid-summer
weather increases the rate of
damage and death to submerged
plants. During spring flooding,
temperatures are colder and
plants can survive longer under
water.
Plants that encounter
flash-flooding along creeks
where the water rises and
recedes quickly are most likely
to survive. They will experience
less oxygen depletion than
submerged plants. Other factors
for survival include water
movement and plant height.
Standing water is more harmful
than moving water. Plants with
some leaves protruding from the
water are more likely to live.
Restoration of alfalfa, irrigated
pastures, perennials and hay will
depend heavily on all of these
factors. But it also depends on
the steps you take toward
recovery.
ALFALFA
Alfalfa can withstand submersion for a limited time, depending on its stage
of growth. Dormant plants may withstand submersion for as long as seven
to 10 days. Growing plants can usually withstand submersion for less than
three to four days without damage.
Alfalfa can recover from moderate silt deposits. Silt deposits of over 2 to 3
inches will weaken the stand, and you may need to regrade and
re-establish in places.
Limit reseeding of established fields to silted patches within the field. If
the entire field is silted, rework and reseed the field. Where alfalfa stand is
over two years old, overseed with temporary crop and reseed alfalfa at
least one month after having reworked the field.
You can reseed small areas with fast-growing grasses. This will help
provide forage until the entire field can be reworked. In old fields, seeding
to annual crops such as ryegrass will provide some hay and also will help
control weeds.
IRRIGATED PASTURES
You probably can restore irrigated pastures without serious production
losses if silt deposits are not over 2 inches and erosion is minimal.
Recovery usually depends on the type of legume. Alfalfa probably will
recover from moderate silting better than white clover varieties. White
clover will not survive silting that covers the ends of the growing stems or
stolons. Ladino clover, however, will fill in stands from a few surviving
plants if the area is not too large.
Grasses such as ryegrass, orchardgrass, fescue and meadow foxtail will
probably grow through a moderate silt deposit, and can stand several days
of flooding without injury. Tall fescue will tolerate more water than
ryegrass or orchardgrass. Meadow foxtail and reed canary grass can stand
longer submersion than other perennial grasses.
Subsurface water saturating the root zone of deep-rooted crops such as
alfalfa can damage the plant as much as surface water. To take care of
excess soil moisture, open drainage ditches as soon as possible.
University of Wisconsin-Extension • Cooperative Extension FLOOD-FARM RECOVERY
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