Integrating Sheep into
Grain and Alfalfa Systems Knocks Back Pests
In Montana, two crop-damaging insects—the
wheat stem sawfly and the alfalfa weevil—have
found comfortable winter refuge in wheat
and alfalfa stubble. The insects raise huge
problems for crop farmers, causing grain
to tip over and alfalfa yields to fall. However,
introducing managed grazing of sheep on crop
residues after fall harvest disrupts the
insects' lifestyles, Sustainable Agriculture
Research and Education (SARE)-funded research
has found.
Moreover, adding sheep brings multiple benefits
to crop producers. By suppressing insects,
sheep save farmers the costs of control measures
like burning, tillage, and insecticides.
Sheep also crimp weed populations, reducing
costly tillage or herbicides during fallow
management. Meanwhile, sheep feed on low-cost
crop residues and do their work without compacting
the soil.
Pat Hatfield, a Montana State University
animal scientist, found through his SARE
research that grazing sheep reduced overwintering
wheat stem sawfly larvae by 67 percent compared
with tillage (51 percent) and burning (48
percent).
In a related study, Hatfield and Sue Blodgett,
MSU integrated pest management coordinator,
found that sheep grazing alfalfa re-growth
in winter and spring reduced overwintering
alfalfa weevil populations by 70 percent
without compromising the yield or nutritional
value of ensuing alfalfa harvests.
There's more than enough sawfly-infested
stubble in Montana's billion-dollar grain
industry to go around, and integrating sheep
into grain and alfalfa production systems
could add an extra income source.
Hatfield says that sheep producers, encouraged
by grazing research now being conducted on
commercial-size plots with economic analysis,
could work alone or in groups through partnership
with grain or alfalfa producers to treat
insect-infested fields.
He sees ruminant grazing of crop residues—in
Montana and around the world—as an
economical and sustainable method of producing
protein like lamb, while allowing people
to enter agriculture without a large outlay
of capital. However, achieving the benefits
will require patience.
"Historically," says Hatfield, "farmers
have been able to see immediate results from
technological advances like fertilizer, pesticides,
and genetically altered plant varieties.
Our program, although less costly, progresses
more slowly, requiring long-term commitments—but
we ultimately anticipate success."
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