Vegetative Mulch Cuts Pesticide Losses in Runoff
ARS News Service
Agricultural Research Service, USDA
Sarah Tarshis, (301) 504-1611, email@example.com
August 25, 1999
Growing vegetables with an organic mulch, hairy vetch--a legume-- instead of
plastic mulch cut pesticide losses by as much as 90 percent in experiments
in Maryland. The vetch also greatly reduced water runoff and sediment
Today, Agricultural Research Service scientists presented the findings--the
first showing the tactic's effect on pesticide loss--at a meeting of the
American Chemical Society in New Orleans. ARS is the USDA's chief scientific
The Chesapeake Bay and its aquatic organisms have long been threatened by
polluted runoff from farms, lawns, golf courses, streets, septic tanks and
other sources. And on the Bay's Delmarva peninsula, runoff from vegetable
fields may contribute to endangering shellfish such as shrimp, clams and
oysters. The new findings point to ways to reduce this threat.
Polyethylene mulch is used to conserve soil moisture and control weeds on
about 4,600 acres of tomato and floral crops in Northhampton and Accomack
counties, Virginia, that make up Virginia's eastern shore. Runoff increases,
however, because plastic covers 50 to 75 percent of the fields. Pesticides
that aren't absorbed into the soil can be removed easily from the plastic
surface by rain.
In a three-year collaborative study, ARS chemist Cathleen Hapeman and her
co-workers grew tomato plants in both plastic-covered and hairy vetch mulch
plots at the agency's Beltsville, Md., Agricultural Research Center. They
measured the runoff and its sediment and pesticide concentrations. Compared
to the plastic-covered plots, the vetch-mulch plots lost about two to 10
times less water, 10 times less soil and, on average, 10 times less
Scientists tested some runoff from the plots on clams and other
bottom-feeding organisms that serve as indicators of water quality.
Preliminary results of the tests, conducted at the University of Maryland's
Chesapeake Biological Lab in Solomons, Md., showed that runoff from
polyethylene plots can harm the aquatic organisms. The organisms were less
affected by runoff from plots mulched with hairy vetch.
Scientific contact: Cathleen Hapeman, ARS Environmental Chemistry Lab,
Beltsville, Md., phone (301) 504-6511, fax (301) 504-5048,
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