Algae blooms from high concentrations of
phosphorus contribute to depleting a waterway of oxygen, thus killing fish and
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Gypsum Helps Curb Runoff of Soil Phosphorus
By Luis Pons
June 20, 2006
Gypsum was the best performer in an
Agricultural Research Service (ARS) study
examining the ability of soil additives to curb runoff of phosphorus from farm
fields into the nation's waters.
In research led by agronomist
Brauerof the ARS
Bumpers Small Farms Research Center in Booneville, Ark., the soft, widely
distributed mineral was the only one of the three soil amendments tested that
reduced soluble soil phosphorus in a field containing more than 10 times the
amount normally found in soils.
The study was done by Brauer, animal scientist
Aiken of the ARS
Production Research Unit in Lexington, Ky., soil scientist
Pote of the Booneville center, and colleagues. The researchers examined how
well gypsum, alum and ground-up wastepaper kept phosphorus from leaching from
farmland. Testing was done near Kurten, Texas, on land that has received manure
applications from dairy and egg-laying operations for more than 40 years.
Excessive use of manures and other fertilizers can significantly increase
phosphorus amounts in the soil. A valuable crop nutrient, phosphorus can run
off and damage waterways by promoting accelerated growth of algae and plants in
streams and lakes. This can deplete oxygen levels in water bodies and adversely
impact living aquatic resources.
The researchers amended the soil annually for three years. They found that
applying 5,000 pounds of gypsum per acre was most effective in reducing
soil-test values for phosphorus. According to Brauer, reductions in dissolved
reactive phosphorus seemed to be dependent on continual applications of gypsum.
Commonly found in sedimentary environments, gypsum is also a by-product of
Brauer explained that gypsum curtails the amount of phosphorus loss by
promoting the binding together of soil particles, thus reducing phosphorus
carried along with sediment. He added that applying wastepaper product
containing aluminum, the active ingredient in alum, can effectively curb
phosphorus, but the large amounts necessary can be impractical.
This work has been described in the Journal of Environmental Quality.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.