OXFORD, Miss. – Pesticides are an important part of modern
agriculture, enabling farmers to grow vast amounts of food
by keeping hungry insects away from the crops. But when
those pesticides wash off the fields and into nearby lakes
and streams, they pose a problem for wildlife and even
people.
Researchers at the University of Mississippi Field Station
are evaluating the possibility that another crop – rice –
may provide a natural, effective way to prevent pesticide
runoff from fouling freshwater resources.
A research team from the USDA-Agricultural Research Service
National Sedimentation Lab is conducting tests and
gathering samples in several rice fields growing at the
Field Station. The study, led by ecologists Charlie Cooper
and Matt Moore of the Sedimentation Lab’s Water Quality and
Ecology Unit and Robbie Kroger, a post-doctoral wetland
ecologist at the Field Station, focuses on the ability of
aquatic plants – in this case, rice plants – to decrease
the contamination levels from pesticide runoff. “Rice is
an interesting plant to use because it is an aquatic plant
that also serves as a food source,” Moore said.
Pesticide runoff generally occurs after rainstorms, so the
team simulates a summer storm – minus thunder and lightning
– and diverts insecticide-laden runoff water into a rice
field. By taking samples at intervals as the water flows
through the field and analyzing them in the lab,
researchers can gauge the levels of pesticides that leach
off into plants, water and sediment.
The scientists are measuring the capability of rice plants
to filter (or capture) insecticides from the water and to
see how the insecticides affect the plant itself. As part
of the project, Kroger is examining pesticide breakdown and
potential release by dead rice plants over several months.
“An interesting contamination question that is often asked
is, Will the pesticide that is on the rice plant be
released back into the water and harm plants and organisms
downstream?'” Kroger said. “We just don’t know yet.
Assessing decomposing rice as well as pesticide
concentrations in the water over several months will tell
us what we need to know.”
However, early results from the project look promising. “It
appears that in the decomposition experiment, the rice
plants’ pesticide concentrations decrease dramatically
during decomposition, and that pesticide does not cycle
from plant to water within the system,” he said. “Most
importantly, water released from these ponds has very small
concentrations of pesticide, concentrations well below
water quality standards.”
The organo-phosphate insecticide used in the study is a
commonly used pesticide for rice and corn. Rice was chosen
for this project not only because it is an aquatic plant
but also because it is a major agricultural crop in the
Delta and in California.
“Eventually I want to do a life cycle study from seed to
seed,” Moore said. “I want to see how much pesticide will
be transferred to the rice plant during the entire growing
season, ending with the harvesting of the seed. Of course,
that includes the rice grain, which may be used for food if
it is free from pesticides.”
This is the second year of the rice study funded by the
U.S. Department of Agriculture in cooperation with the
Field Station. Ray Highsmith, director of the UM Center for
Water and Wetland Resources and the Field Station, and
Marge Holland, professor of biology, are the university’s
principal investigators, and Charlie Cooper serves as the
USDA’s project coordinator.
“The National Sedimentation Lab scientists, in cooperation
with Dr. Holland, have been very important partners for
the center and Field Station,” Highsmith said. “They have
been conducting related studies at the Field Station for
many years. This research is important not only for the
agricultural industry and wildlife managers but also for
society that depends upon sources of clean water.”
For more information on the UM Field Station, go to