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Pest Management
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Pulse crops like peas can "fix" nitrogen
for a subsequent crop. Crop diversity also can lower input costs such as herbicides and pesticides.
– Photo by Eric Nielsen |
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Diverse, pest-resilient fields contain rich supplies of above- and below-ground
beneficial organisms. Such organisms can:
 antagonize
insects and nematodes
inhibit
growth of disease organisms
boost
crops’ natural defenses
suppress
some weeds by exposing weed seeds to more predators and decomposers
release
nitrogen more slowly, giving larger-seeded crops a head start
in spring
Crop diversity can lower input costs, studies show. In an Ohio State University
study, average per-acre costs for herbicides and insecticides were only $20
for a corn-soybean-wheat-hairy vetch rotation, compared with $36 for a typical
corn-soybean system. In Alabama, scientists found that two years of switchgrass
provided equivalent root knot nematode control as continuous peanuts with nematicide.
In Maryland, two years of a sorghum-sudangrass summer crop, combined with poultry
litter, effectively stemmed root knot nematodes in potatoes.
For more information on the many benefits of diversification to
pest management, see SAN’s ‘Naturalize’
Your Farming System: A Whole-Farm Approach to Managing Pests.
Reduced Water Use
In the nation’s drier regions, many farmers use rotational strategies
to conserve soil moisture or harvest a crop despite drought. Many, in fact,
frequently fallow their land – leaving it idle to accumulate moisture
for the following crop. In 1997, 22 percent of the nation’s wheat was
grown in wheat-fallow rotations. Fallow periods, however, expose soil to wind
and water erosion and organic matter loss. Moreover, a more diverse rotation
can improve yields.
A long-term study at the University of Wyoming found that partially replacing
fallow with Austrian winter peas improved water use efficiency, added nitrogen
to the subsequent wheat crop and provided a nutritious forage for lambs. Researchers
direct-seeded peas into wheat stubble in late summer. In late spring, they turned
lambs out to graze the peas for three weeks, resulting in better gain –
and profits. Planting peas every fourth year increased net return per acre from
$7 to $13, averaged over the four years. Moreover, while summer fallow generally
only saves 20 to 40 percent of precipitation, the peas used rain or snow otherwise
lost to runoff and soil evaporation.
University of Wyoming researcher Jim Krall praises the potential for the winter-hardy
medic Medicago rigidula. In winter annual pastures alternating with wheat, M.
rigidula reseeds itself reliably in fall and has produced more than 3,700 pounds
of dry matter per acre by mid-May.
Proso millet needs the least amount of water of any cereal. Shallow rooted,
it doesn’t tolerate drought as much as it evades it by maturing in 60
to 90 days after planting. Its low straw-to-grain ratio also contributes to
its water-use efficiency. In moisture-limited areas of the central Great Plains,
winter wheat-proso-fallow rotations provide an extra cash crop every three years.
The alternative oilseeds sunflower, canola and crambe – one of the richest
known sources of erucic acid, used in industrial lubricants – are all
feasible in dryland rotations with winter wheat in that region.
In northern Idaho, condiment mustard’s 4-foot effective rooting depth
extracts more soil moisture than peas or lentils, which is helpful in low-rainfall
years. All three rotation crops are very good at breaking up disease, insect
and weed cycles in cereal crops, but mustard’s more plentiful residue
does a better job of protecting erosion-prone winter soils: studies show it
maintains greater than 50 percent surface cover, compared with 30 percent for
pea and 25 percent for lentil.
Encouraging prices have prompted “steady adoption” of condiment
mustard by the region’s farmers, said University of Idaho extension specialist
Stephen Guy.
Water Quality
In diversified systems that border sensitive waterways, riparian buffers strips
comprised of trees, shrubs and grasses intercept sediment, nutrient and pesticide
runoff. Forested riparian buffers help to reduce stream bank erosion, protect
water quality, enhance aquatic environments and provide wildlife habitat.
According to USDA’s Natural Resources Conservation Service (NRCS), buffer
strips can remove up to 50 percent of nutrients and pesticides, up to 60 percent
of certain pathogens and up to 75 percent of sediment that might otherwise leave
a field.
“In some cases, installing buffers helps producers comply with environmental
laws and regulations,” said Steve Carmichael, NRCS state resource conservationist
in Louisiana. “It offers an effective way a producer can demonstrate concern
for the environment and a commitment to good land stewardship.”
USDA offers financial and cost-share assistance to producers interested in
planting and maintaining buffers through the Conservation Reserve Program and
the Environmental Quality Incentives Program. See <www.nrcs.usda.gov/programs/>
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