story to find out more.
Giant reed, which has shown the greatest biomass
production potential for floating platforms on wastewater lagoons, is examined
by technician Bobby Shiver (left) and soil scientist Robert Hubbard just before
harvesting. Click the image for more information about it.
Floating Plant Mats Help Clean Manure Lagoons
August 1, 2006
Studies have shown that its
possible to remove excess nutrients from manure lagoons by growing plants on
floating mats. Agricultural Research Service (ARS) scientists in Tifton, Ga., have been
studying how to most efficiently use this method to extract excess nitrogen and
phosphorus from wastewater so it wont become an environmental problem.
Hubbard, in the ARS
Watershed Research Unit at Tifton; plant pathologist
Wilson and geneticist
Anderson at the ARS
Genetics and Breeding Research Unit in Tifton; and colleagues Larry Newton,
John Ruter and Gary Gascho at the University of
Georgia are trying to determine the feasibility of removing excess
nutrients in this way.
Lagoons are commonly used to store wastewater from confined-feeding dairy
and swine operations. The nutrient-laden water is generally applied to land as
fertilizer. But if its not applied properly, any excess nitrogen and
phosphorus may eventually contaminate drinking water, impair soil quality and
cause dead zones in surface waters.
One research phase has been completed and a second is under way. The first
phase was conducted in small tanks, the mats tested on full-strength
wastewater, half-strength wastewater, or an inorganic solution. Vegetation was
grown atop floating rafts constructed of PVC pipe and chicken wire that was
covered with jute erosion-control matting.
In that phase, cattail grew the best on full-strength wastewater, produced
the most biomass, and removed the most nutrients. Studies showed that
harvesting cattail from the floating rafts could remove an average of 493 grams
of nitrogen and 73 grams of phosphorus per square meter per year.
Now the second phase of research is being conducted at
Southern Select Farms, a
commercial hog farm in Tifton that has a single anaerobic lagoon. A new type of
floating mat, consisting of plastic foam covered with braided coirthe
coarse fibers from the outer shell of coconutswill be tested. It was
designed in cooperation with Maryland and
Charleston Aquatic Nurseries,
located in Jarretsville, Maryland, and Johns Island, South Carolina,
Several different plant species seem to be good candidates, including St.
Augustine grass, coastal Bermudagrass, and giant reed, which have potential as
a source of bioenergy fuel.
more about the research in the August 2006 issue of Agricultural
ARS is the U.S. Department of
Agricultures principal scientific research agency.