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New Proof About Buffers
By
David E. Wilson, Jr.
new Agricultural Research Service report released last month shows
how important forest buffers are to curbing nitrogen and phosphorous
runoff.
n
arm of the US Department of Agriculture, the service took nine years
to complete its groundbreaking work which shows that native plant
buffers retained or removed at least 60 percent of the nitrogen and
65 percent of the phosphorus that entered from adjacent manure/fertilizer
application sites. This is the first time that a study of a restored
riparian buffer has shown that the retention of phosphorus was as
high or higher than nitrogen retention.
 n
their "Designing the Best Possible Conservation Buffers,"Agricultural
Research Service scientists Richard Lowrance and engineer George Vellidis
of the University of Georgia wanted to find out exactly what grass
and forests buffers were capable of.
 he
buffer system used in the long-term study had three zones of grass,
new forest, and old forest. To get a baseline of runoff amount and
content researchers monitored both nutrient levels put on the field
as well as nutrient levels leaving the field prior to buffer planting.
 or
the next nine years, they monitored amounts of water and concentrations
of nutrients in water entering and leaving the riparian wetland. Generally,
young forests have high nutrient uptake rates because the plants within
them are growing more, while mature forests provide forest soils (leaf
litter and shallow roots) which increase biomass on the forest floor.
All these factors are keys to reducing the movement of nutrients to
surface waters.
 ut
when the scientists found they could reduce phosphorous flow by two
thirds, they were shocked. "Most of our management recommendations...
have focused on nitrogen," Lowrance said in a USDA interview in December,
"now we know that a restored riparian forest buffer can be just as
effective for phosphorus removal."
he study was in response to a request made in the late 1980s and early
1990s by USDA's Natural Resources Conservation Service and Forest Service to
recommend riparian buffer specifications. At that time, the general
recommendation was that natural mature buffers should be used, but USDA
needed national specifications based on the best science.
o
compliment this work, another study is now being conducted by soil
scientist Robert Hubbard and animal scientist G.L. Newton of the University
of Georgia to evaluate effectiveness of grass-forest buffers to filter
nutrients from fields. They have so far found that nutrient uptake
for the grasses is limited, with uptake of nitrogen at about 45 percent
and phosphorus at around 20 percent. The research shows that grass
buffers work better when combined with other buffer systems such as
forest.
n
another study headed by Lowrance and Vellidis, herbicides were examined
in a grass-forest buffer system. During this 3-year study, they found
that the grass filter strip buffers were especially effective at reducing
the amounts of two herbicides, atrazine and alachlor, that entered
the shallow groundwater and surface runoff. Atrazine has been pinpointed
as a hormone disrupter and cause of malformations in frogs and salamanders.
In contrast to the results with nitrogen and phosphorus, the grass
filter strip received higher amounts of herbicides and provided a
higher rate of removal.
he crux of their work concludes that a combination of forest and
grass buffers is best for curbing both chemical and nutrient runoff.
Pennsylvania farmers and property owners would do well to utilize
these federal programs and lobby for more state supplements, which
in Maryland, have added thousands of acres of forest buffers to streams
and ditches. In addition to the wildlife habitat that buffers create,
their ability to protect water quality in Pennsylvania streams and
rivers should make them one of the highest priority conservation tools.
"Designing the Best Possible Conservation Buffers" was published
in the December 2003 issue of Agricultural Research magazine. Information
for this article was provided by the USDA'a Agricultural Research
Service.
Contact Dave Wilson
See past topics of In the Flow here!
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