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Mississippi Delta MSEA
Ecologists Charlie Cooper (left) and Scott Knight sample bottom sediments in
Thighman Lake, Mississippi, for small invertebrates that indicate ecosystem
health.
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Grower-assisted research helps curb water pollution.
Floyd Anderson, Jr., has a special present for his young son, Will. It will
be perfect for father-son fishing trips.
Anderson, a farmer in the Mississippi Delta region, has a 40-acre oxbow lake
stocked with bass and catfish 300 yards behind his house. Thighman Lake is the
boy's gift. Anderson is participating in an Agricultural Research Service program to
improve water quality in oxbow lakes. By doing so, he has helped preserve
Thighman Lake for his youngest son.
"The biggest impairment to fish in oxbow lakes is sedimentnot
farm chemicals," says ecologist Scott S. Knight, who is with the ARS
National Sedimentation Laboratory in Oxford, Mississippi. "That's why we
need to find ways to keep the soil in place on farms."
But Thighman is just one example. Visibility in the water of nearby Deep
Hollow Lake has improved to a depth of more than 15 inches, increasing the
amount of algae, fish, and even turtles.
Change at Thighman is less dramatic, but it's made Anderson excited about
the possibility of fishing there.
Anderson, 45, grew up on the family farmthe Anderson Planting Company.
He grows soybeans, corn, rice, and sometimes cotton on his 4,300 acres. His
lake is part of a large-scale initiative to evaluate how environmentally
friendly farming practices can benefit oxbow lakes. Its official title is the
Mississippi Delta Management Systems Evaluations Area, or MSEA.
Seventeen farmers cooperate with ARS, the U.S. Geological Survey,
Mississippi Water Resources Research Institute, and others who are conducting
scientific experiments in the project. Anderson says the project has given him
and other Mississippi farmers a lift: It has restored their unfairly tarnished
reputations.
Floyd Anderson, Jr., and his son, Will, check out possible fishing holes in
Thighman Lake.
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"The public never sees all I do to protect the land," says
Anderson. "Why would I make 10 or 12 tilling trips across a field and
erode my soiland pay $6 an acre each time to do itwhen 3 or 4 trips
will do?"
Delta Farmers Try Cover Crops
The 5-year, multimillion-dollar Mississippi Delta MSEA comprises about 7,320
acres of farmland around three lakes: Thighman, Beasley, and Deep Hollow, in
Mississippi's Sunflower and Leflore Counties.
"The project has been an enormous undertaking," says ecologist
Charlie Cooper. He heads Oxford's Water Quality and Ecological Processes
Research Unit at the sedimentation lab.
"Most farmers are naturally inclined to experiment," he says.
"We have to have flexible research and build on what we learn each
season."
For example, cover crops like the wheat and rye planted in Deep Hollow's
watershed protect the soil from winter's pelting rains but need to be replanted
every year. ARS agronomist Seth M. Dabney at Oxford may have an alternative,
and he's trying it on Anderson's farm.
Microbiologist Robert Zablotowicz uses thin-layer chromatography to study
metabolism of herbicides by lake bacteria and algae.
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"Balansa clover adds about 75 pounds of crop-feeding nitrogen per acre
to the soil every year it's used. It produces lots of seeds, so farmers don't
have to replant annually," says Dabney. "And it does well in the
Southeast Cotton Belt."
In springtime, the clover's white flowers attract honey bees. After the
plants die, they add organic matter to the soil, which can improve crop
productivity.
Preserving Farmers' Reputations
"Farming's all I've ever done, and it's all I ever want to do,"
Anderson says. "To learn that the groundwater was not polluted and we're
not leaking chemicals like some people saythat has been worth whatever
I've done for the project, just to find out that's not the case."
ARS chemist Sammie Smith, Jr., drilled wells in the watersheds surrounding
the three test lakes to monitor for 18 different agricultural chemicals at 5-,
10-, and 15-foot depths.
That's about 100 MSEA wells. Over 3 years, only 5 of more than 600 well
samples showed any pesticide traces. Even then, the amounts were usually found
shortly after a field application and were well within the limits allowed for
drinking water.
Another groundwater concern is nitrate-nitrogen contamination. This is a
special risk for infants.
Soil scientist Jonathon D. Schreiber had been checking wells for this
potential contaminant and he, too, found the water was safe for drinking.
"We wanted sound sciencenot sound biteson farming and the
environment," says Frank Gwin, a retired farmer who serves as the MSEA
project's liaison between researchers and farmers. "If the news had been
bad, we'd have wanted to know. But it seems we have a clean bill of
health."
Soil Microbes That Cut Pollution
Biological technician Terry Welch identifies fish and measures their lengths
and weights to evaluate changes in fish communities resulting from new
watershed management practices.
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Scientists from Stoneville, Mississippi, are exploring how beneficial
enzymes, microbes, and algae are increased by conservation practices. These
microbes may help remove chemicals and enhance soil.
"We hope to better understand how microbial populations improve water
quality by degrading pesticides," says soil scientist Martin A. Locke. He
heads the ARS Southern Weed Science Research Unit in Stoneville. "This
knowledge is essential for developing management practices that maintain
diverse aquatic microbial populations that are effective in pesticide
breakdown."
Microbiologist Robert M. Zablotowicz, who is in Locke's unit, teamed with
Knight to find that Deep Hollowwith the most conservation practices in
use of any of the MSEA watershedshad the least sediment and the highest
algal population of the three lakes. Algae are vital to the lakes' health,
forming the basis of the food chain, for starters. But that's not all.
"Certain species of one-celled green algae in the lake can metabolize
specific soil-applied herbicides, such as atrazine and fluometuron," says
Zablotowicz. "We also found a kind of bacteria called fluorescent
pseudomonads. These can also degrade certain herbicides."
The right farming practices can boost the soil's microbial
pollution-stoppers.
Soil Quality's Another Key
"Soil quality means many things to many people. The factors we are
looking at include increasing organic matter and improving the balance of plant
nutrients, like nitrogen and phosphorus, that play a role in soil
productivity," says Locke.
Cover crops can improve the soil by enhancing the food supply for living
thingsinsects, spiders, worms, and microbesthat help make the soil
porous, says Dabney. He is evaluating tilling methods that won't disturb cover
crops but will break up hardened soil.
Some farmers believe reduced tillage and cover crops will open the door to
diseases, weeds, and reduced yields. If MSEA demonstrates this doesn't have to
happen, more farmers will be willing to try these practices.
Cover crops prevent erosion and add nitrogen to the soil. Here, technicians
Earl Gordon and Jennifer Tonos collect samples so they can estimate the amount
of plant matter in a field near Thighman Lake.
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"Limited information is available on the effects of reduced tillage and
cover crops in cotton production systems," says Locke. "Our initial
goals were to characterize the differences in the biological, chemical, and
physical soil properties in the Beasley and Deep Hollow watersheds, where
different cotton management practices are used."
At Deep Hollow, Dabney is testing gypsum, or calcium sulfate, as a way to
help with yields. "People have been using lime for centuries to reduce
soil acidity and build up calcium, an essential element for plants," he
says. "ARS research at West Lafayette, Indiana, has shown that gypsum lets
more rain soak into the soil and reduces erosion."
Keeping Weeds in Check
Differences in soil properties can influence how agricultural chemicals
react. Knowledge of those differences and of weed populations in the three
watersheds will help determine proper herbicide and fertilizer applications.
The information will also allow the use of computer-driven systems in weed
control and other farm chores.
"Areas with soils with higher organic matter content and clayey texture
tend to have more weeds and more herbicides binding to the soil," Locke
says. "With reduced-tillage cotton and soybeans, weed populations were
higher than with conventional tillage. But most weeds were adequately
controlled with postemergence applications using shielded sensor
sprayers."
Deep Hollow grower Philip Barbour's farm was the test site for a hooded
sensor sprayer that helped him reduce herbicide costs dramatically.
"That hooded sensor sprayer is something I'd like to try," says
Anderson. "I noticed it saved Philip a lot of money."
Agricultural engineer James E. Hanks worked with Patchen, Inc., of Los
Gatos, California, to develop and test the eight-row hooded sprayer. Hanks is
in Stoneville's Application Production and Technology Research Unit.
The sensor distinguishes differences in light reflected from bare soil
versus weeds in the area between rows of planted crops. The sprayer applies
herbicides only where weeds are present. Hanks ran the sprayer's Deep Hollow
tests.
To determine nutrients in shallow ground water, chemist James Hill places water
in an autosampler of the flow-through colorimetric autoanalyzer.
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"We evaluated the weed sensor as a way to cut herbicide use for cotton
and soybeans grown under conservation tillage," says Hanks.
"Herbicide savings averaged 63 percent on 105 acres of cotton and 49
percent on 115 acres of soybeans during a 3-year study."
"And the less herbicide used, the less the potential for adverse
environmental impact."
Botanist Charles T. Bryson, who is in Stoneville's Weed Science Unit, has
been recording levels and shifts in weed populations in various cotton and
soybean fields at Deep Hollow watershed. The data will be used to enhance the
hooded sensor sprayer's capacities.
"Weed species and populations increased with fewer tillage
operations," says Bryson. "But identifying which weeds are present
allows the farmer to target a specific troublesome weed with certain tillage
practices or herbicides. Mapping weed populations within fields also allows for
variable herbicide application rates."
Bryson's research already shows that the equipment is highly effective as it
is.
"I have taken data on weed populations following the use of the hooded
sensor sprayer," says Bryson. "Most of the weeds are controlled as
effectively with the sensor sprayer as with traditional cultivation."
Nature's Living Filters
Low tillage and the hooded sensor sprayer are exciting parts of MSEA, but
nature has its own method of protecting the water. Both Deep Hollow and Beasley
have wooded areas near their banks that serve as buffers between lake and farm.
Ecologists call these natural bank barriers riparian zones.
"Riparian zones and wetlands are fragile parts of the Delta ecosystem
and serve as living filters to protect oxbows from agricultural chemicals and
sediment," says Locke. "Restoring and preserving them make sense if
we want to enhance soil and water quality."
ARS scientists from Oxford and Stoneville, along with Mississippi State
University scientists, have been looking at Beasley's riparian zones. They
found that because of forest litter, the soils have the potential to rapidly
bind pesticides and break them down.
Left to right: Project coordinator Frank Gwin, farmers T.A. Murtagh and David
Walker, and soil scientist Martin Locke review an aerial map of Mississippi
Delta counties involved in the Management Systems Evaluations Area project.
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Farmers and others can create additional natural barriers using a filter
strip of strong, tall grasses. ARS asked USDA's Natural Resources Conservation
Service to plant filter strips around Beasley and Deep Hollow.
Stoneville ecologist William J. Staddon, who is also in Locke's unit, found
that the vegetative residue in the filter strips enhance microbial life in the
soil, increasing its ability to break down the herbicide metolachlor used in
soybeans and cotton.
The filter strips and other vegetative barriers may even help manmade
erosion controls be more effective. One popular practice is called an overfall
pipe. Farmers build a small ridge around their field and install a pipe to
carry water away from the field without causing erosion.
Boards can be used to partially block the inlet to these overfall pipes
during the winter, creating shallow ponds. The ponds protect the soil from
winter's pelting rain and give sediment a chance to settle out. By releasing
storm water slowly, downstream flooding is reduced.
When the boards are removed in the spring and summer for planting crops,
however, the pipes alone don't trap enough sediment to keep the lakes clear.
"Adding a tall grass barrier in front of the pipe inlet will help keep
soil from leaving the field," says Dabney.
It seems the grasses do their job by slowing the water just enough to allow
the sediment to settle, without flooding the crops.
When farmers hold water on the fields in the winter, the ponds attract
ducks. This can mean extra farm income from hunting. Between the ducks and the
flooding, weeds in the field are reduced, so the farmer needs less herbicides
when the temporary ponds are drained.
"That's the great thing about MSEA," adds Cooper. "We find
things that benefit people and natureit's a winning
combination."By Jill
Lee, and Tara
Weaver-Missick, Agricultural Research Service Information Staff.
This research is part of Water Quality and Management, an ARS National
Program described on the World Wide Web at
http://www.nps.ars.usda.gov/programs/nrsas.htm.
Charles M. Cooper is in
the USDA-ARS Water
Quality/Ecological Processes Research Unit, 598 McElroy Dr., Oxford, MS
38655-2117; phone (601) 232-2935, fax (601) 232-2915.
Martin A. Locke is in the USDA-ARS
Southern Weed
Science Research Unit, P.O. Box 350, Stoneville, MS 38776-0225; phone (601)
686-5272, fax (601) 686-5422.
"Mississippi Delta MSEA" was published in the
June 1999 issue of Agricultural
Research magazine.
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