Stopping Erosion with Gypsum and
To evaluate the effect of PAM on soil erosion, (left to right) Purdue
University Ph.D. Candidate Eusebio Ventura collects runoff water to measure
sediment while graduate student Belle Wallace, ARS soil scientist Darrel
Norton, farmer Ralph Woodward, and graduate student Katerina Dontsova observe
and assist with trials.
In the late 1700s, Benjamin Franklin, whose interest in scientific
experiments is now legend, demonstrated the value of a natural geological
substance called gypsum, used in making plaster, as a soil amendment.
On a prominent hillside, Franklin applied gypsum in a word pattern that
read, "This land has been plastered." The increased grass growth in
the area on which the gypsum had been applied served as an effective
demonstration of its value as a fertilizer.
Two hundred years later, gypsum is again being studiedthis time as a
way of controlling erosion by increasing water infiltration.
"New technologies to improve air quality have produced more and more
gypsum byproducts with potential for beneficial use in agriculture," says
ARS soil scientist L. Darrell Norton. He is at the
National Soil Erosion Research
Laboratory (NSERL) in West Lafayette, Indiana. "The removal of sulfur
from flue gases in coal-fired power plants has resulted in immense stockpiles
of these byproducts that can supply sulfur to crops and may also serve as a
"Each year, power plants produce about 100 million tons of gypsiferous
material, high in calcium and sulfur, as a byproduct of capturing sulfur
dioxide emissions," says W. Doral Kemper, who formerly led the ARS
national program in soil management research. "That's enough to apply a
ton per acre to a quarter of U.S. farmland."
Norton and Kemper believe that recycling these low-cost byproducts of
industry to control erosion and increase yield is a win-win situation. They say
gypsum can be used on many soils nationwide to improve water infiltration and
help plant growth.
The two believe the increased yields are explained by studies conducted by
ARS soil scientists K. Dale Ritchey at Beaver, West Virginia, and Ronald F.
Korcak at Beltsville, Maryland, and their coworkers. These studies have shown
that calcium from gypsum applied to acidic soils gets down into the subsoil
where it is needed, so crop roots can grow deeper and access more water.
Norton says, "Using gypsiferous byproducts would give farmers a
low-cost remedy for acid, sodic, and erosion-prone soils."
Several years ago, ARS scientists at the NSERL worked with world-renowned
soil scientist Isaac Shainberg, who is now director of the Volcani Institute in
Israel. They wanted to determine how electrolytes, which are natural electrical
conductors in rainfall and runoff water, could affect estimates of soil
erodibility. During Shainberg's visit, the idea of using gypsum and other soil
amendments to control soil erosion by water from agricultural fields was also
Soil scientists Darrell Norton (left) and Ralph Woodward, a cooperating corn
farmer, assess the effect of field application of gypsum on plant root growth.
"We suspected that gypsum could reduce surface sealing and improve
water entry and reduce erosion," says Norton. "In lab studies, we
found the powdered waste product releases electrolytes that keep clay particles
clumped together, reducing crusting."
About the same time, Shainberg became interested in another white
powderPAM, short for polyacrylamidea material used in water
treatment plants as a flocculent to clean up the water by precipitating small
"According to the literature, you could stabilize a soil with PAM, but
it was very expensive for practical use when mixed in the entire plowed
layer," says Norton. A series of lab studies conducted by Shainberg and
ARS scientists on some small flumes confirmed that as little as 5 to 10 parts
per million of PAM mixed with water almost eliminated rill erosionthe
tiny gullies caused by water moving over the soil.
At the NSERL, Norton and Shainberg, working with three ARS
colleaguessoil microbiologist Diane E. Stott, agricultural engineer John
M. Laflen, and soil scientist Joe M. Bradfordstudied how adding PAM both
to simulated rainfall water and to the soil surface affected erosion. They soon
came to recognize that if the soil surface could be stabilized down to just a
very small depth, erosion might be greatly reduced.
"Most important," says Norton, "was the finding that PAM
didn't have to be mixed into the soil. Only the surface layerless than
the top one-sixteenth inch or less of soilhas to be treated, to let water
into the soil." NSERL agricultural engineer Dennis C. Flanagan, working
with Norton and Shainberg, conducted field tests to examine how effective both
gypsum and PAM could be at controlling soil loss on a steep and erodible silt
loam soil. They tested surface applications of 2.2 tons per acre of gypsiferous
byproduct from the Purdue University power plant in West Lafayette, Indiana, as
well as a liquid solution of 18 pounds per acre of PAM sprayed on the soil and
allowed to dry.
They found that the byproduct improved infiltration and could potentially
reduce runoff and erosion problems on similar U.S. soils. The PAM surface
treatment was very effective at controlling rill erosion, even for water
inflows up to 16 gallons per minute per rill.
Samples of runoff water examined by soil scientist Darrell Norton were
collected from an experimental plot in farmer Ralph Wood's gypsum-treated
cornfield in Carlisle, Indiana.
"PAM is a polymer produced from petrochemicals," says Stott.
Efforts are under way with ARS researchers at the
National Center for Agricultural
Utilization Research in Peoria, Illinois, to develop a cheaper,
Stott and ARS soil scientist Rodrick D. Lentz at
, have tested many
commercial synthetic PAM forms to pinpoint desirable characteristics. So far,
they've found some types of PAM materials work better than others to reduce
crusting, increase water infiltration, and promote seedling emergence.
lab experiments in 1992 showed that gypsum byproducts tested on three soils,
using simulated rainfall, produced some valuable results. A byproduct of almost
pure gypsum from a special coal-burning technique in power plants increased
water infiltration and reduced soil loss by about one-fourth. A type of gypsum
left over from fertilizer manufacturing did almost as well in reducing soil
loss between rows.
Other related work at NSERL includes the blending of several byproducts like
fly ash and organic-rich industrial sludge. This appears very promising, says
Norton, in producing a high-organic-matter, high-nitrogen, and high-phosphorus,
soil-like material that is environmentally friendly.
Adding a tracer dye enables graduate student Katerina Dontsova to measure the
velocity of water flowing across an experimental plot.
This work has been done cooperatively with Purdue researchers and has
received funding from several Indiana sourcesthe Eli Lilly Company,
Lafayette; Purdue University power plant, West Lafayette; Amax Coal Company,
Brazil; and the Indiana Department of Commerce, Indianapolis.
Now that Norton and NSERL scientists have documented some of the chemical,
physical, and biological processes that occur on soils that have gypsum
applied, they are currently studying the effects on crop yields.
Cooperating farmers report encouraging results. In one of over 50,000 acres
of field tests, Ken Curtis of Prairie City, Illinois, used high-purity gypsum,
a scrubber byproduct from a coal-fired unit of City Water, Light, and Power of
Springfield, Illinois. He applied 3 tons of gypsum per acre to a 20-acre field
of no-till soybeans, randomly applying various amounts.
"Treated soybeans yielded 63 bushels per acre4 bushels more than
the nongypsum control. I didn't expect that much response so quickly,"
Norton plans to expand the test acreage to further assess benefits of gypsum
on wheat, corn, and soybeans in several eastern states. By Hank
Darrell Norton is at the USDA-ARS National Soil Erosion Research
Laboratory, 1196 Soil Bldg., Purdue University, West Lafayette, IN; phone: