United States
Environmental Protection
Agency
Solid Waste
and Emergency Response
(5306W)
EPA530-F-97-044
October 1997
www.epa.gov
Innovative Uses of Compost
Disease Control for Plants
and Animals
ompost technology is a valuable tool already being used to
increase yields by farmers interested in sustainable agriculture.
Now, professional growers are discovering that compost-
enriched soil can also help suppress diseases and ward off
pests. These beneficial uses of compost can help growers save money,
reduce their use of pesticides, and conserve natural resources. In the poul-
try industry, composting has also become a cost-effective method of mortal-
ity management. It destroys disease organisms and creates a nutrient-rich
product that can be used or sold.
Plant Disease Control
ach year, more than 10 percent of the vegetables planted in the
United States are lost to root rot alone, according to researchers
at the University of Florida's Tropical Research and Education
Center. Additional crop losses are caused by other soilborne
plant pathogens, such as the micro-organisms that cause ashy stem blight
and chili pepper wilt. Compost can help control plant disease and reduce
crop losses. Disease control with compost has been attributed to four possi-
ble mechanisms: (1) successful competition for nutrients by beneficial
micro-organisms; (2) antibiotic production by beneficial micro-organisms;
(3) successful predation against pathogens by beneficial micro-organisms;
and (4) activation of disease-resistant genes in plants by composts.
Scientists have enhanced the natural ability of compost to suppress
diseases by enriching it with specific disease-fighting micro-organisms or
other amendments. This amended or "tailored" compost can then be
applied to crops infected by known diseases. Research has shown that tai-
lored compost significantly reduced or replaced the application of pesti-
cides, fungicides, and nematicides—which could adversely affect water
resources, food safety, and worker safety.
> Printed on paper that contains at least 20 percent postconsumer fiber.
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The use of tailored compost can also be more
cost-effective than chemical soil treatments, such as
methyl bromide. Soil treated with compost retains
irrigation water better, which lowers water costs.
Chemicals also must be applied more often than
compost. In addition, some chemicals have re-entry
requirements that prohibit workers from entering a
field immediately after chemicals have been applied,
reducing worker productivity.
Compost Impedes Pythium
Root Rot
Dr. Harry Hoitink of The Ohio State University,
has conducted compelling research on compost's
effects on plants afflicted with Pythium root rot. As
the photo below illustrates, the application of tai-
lored compost had a dramatically positive effect on
plant growth and impeded the spread of the disease.
Photo courtesy of Dr. Harry Hoitink, University of Ohio
The plant on the right was treated with compost. The plant on
the left was not and suffered the effects of Pythium root rot.
Dr. Hoitink views the disease-suppressive charac-
teristics of compost as a reason to consider widen-
ing compost applications, "Those who believe
composting is not practical for large acreages would
find Brazil interesting. I visited a sugar cane farm of
some 150,000 acres where the bagasse [stalks left
after harvest] was composted and applied back on
the land. Every acre got a treatment once every 5
years with 15 percent increases in yield. Some of
that increase is apparently due to a suppression of
disease organisms."
Compost Combats Chili Wilt
Researchers from New Mexico State University
applied a compost made from municipal wastewater
sludge and yard trimmings to chili crops in a field
known to be infested with Phytophthora root rot, or
chili wilt. Four different quantities of compost were
applied: 10, 20, 30, and 50 tons per acre. Another
section of the field, where no compost was applied,
was used as a control area. Data collected included
damping off disease effects, plant height, chili wilt
infection, and yields.
The study showed that salt content in compost
plays an integral role in suppressing diseases and
increasing crop yields. The 10-ton and 20-ton com-
post applications provided the greatest suppression
of chili wilt and the highest yields. The 50-ton treat-
ment resulted in the poorest yields. The control
acreage and the 30-ton application also produced
poor yields. The losses in the 30- and 50-ton
acreages were attributed to high salt concentrations
in the compost, which weakened the plants and
made them more susceptible to chili wilt. For opti-
mal results, therefore, salt concentrations in compost
should be measured and application rates adjusted
accordingly. Plant salt sensitivity requires a tailored
compost controlled for salt concentration.
Compost Abates Ashy Stem
Blight and Root Rot
University of Florida researchers tested the effects
of Agrisoil (compost made of mixed municipal solid
waste) and Daorganite (a heat-treated biosolids mix),
on test plots in a field in Homestead, Florida. The
Agrisoil compost was applied at rates of 36 tons per
acre and 72 tons per acre, and the Daorganite sludge
was applied at rates of 0.67 tons per acre and 1.33
tons per acre. Sections of the field also were left
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untreated as a control. Six weeks after the materials
were incorporated into the soil, researchers planted
bush beans throughout the field. A second crop,
black-eyed peas, was planted following the bean
harvest, and Agrisoil compost and Daorganite were
applied at the same rates as in the bush bean project.
The field was also fertilized according to accepted
local agricultural practices.
The health and yields of the bush bean crops
were significantly improved by compost. Beans
grown in the Agrisoil compost were larger and
healthier. Yields from the 36 and 72 tons per acre
application areas were both 25 percent higher than
control area yields. Beans grown in the Daorganite
mix showed low yields similar to those grown in the
control areas. In addition, ashy stem blight severely
affected beans grown in both the control and
Daorganite-treated areas, but not the plots with
Agrisoil compost.
The health and yields of the black-eyed pea crops
grown in compost were also significantly improved.
These crops had greener foliage and were larger than
those grown in the control or Daorganite-treated
plots. Yields from the compost-enriched areas were
more than double the control yields in the 72 tons
per acre application sections and also significantly
higher in the 36 tons per acre sections. By compari-
son, yields in the Daorganite-treated areas were only
slightly higher or comparable to those in the control
sections. Rhizoctonia root rot severely affected plants
in the Daorganite-treated and control areas, but the
disease was considerably less prevalent in the com-
post-enriched areas.
In this particular study, yields and disease infec-
tion proved to be directly related in both the bean
and pea crops. Mature Agrisoil compost was more
effective at disease suppression than the Daorganite
heat-treated biosolids mix. Thus, yields were uni-
formly higher in the Agrisoil-treated areas than in the
Daorganite-treated and control areas.
Mortality Composting
More than 7.3 billion chickens, ducks, and
turkeys are raised for commercial sale in the
United States each year, according to U.S.
Department of Agriculture's National Agricultural
Statistics Service. About 37 million birds (18-25
percent) die from disease or other natural causes
before they are marketable. As more poultry is
consumed, these numbers are expected to climb.
Composting is a viable and cost-effective option
for disposing of poultry mortalities as compared to
incineration or burial. Pathogens in poultry carcasses
are destroyed during composting by the high temper-
atures (130-155 degrees Fahrenheit) inherent in the
process.
During composting, various odor control tech-
niques can be used. As a result, this type of com-
post is not only safe for crop application, but it
also can be safely sold by farmers. In fact, selling
excess compost could even be a source of addi-
tional income for farmers. Markets for high-quality
compost include professional growers (such as
horticultural greenhouses and nurseries), home-
owners, turf growers, and crop farmers (such as
corn and wheat farmers). Professional growers
alone purchase $250 million per year in compost
products.
Pest Control
ompost also can eradicate some types of
pests, such as parasitic nematode
(worm) infections, in addition to its use
in controlling disease. Specially formu-
lated (tailored) compost can include chemicals that
actually kill nematodes or prevent their eggs from
hatching. Most types of compost help control para-
sitic nematodes by providing nutrients to the soil,
which encourage the growth of fungi and other
organisms, which, in turn, compete with or destroy
nematodes. Compost also contributes to plants'
basic health, making them less susceptible to pests.
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Compost's ability to halt soil nematode invasion
was identified by the staff of Dr. Herbert Bryan of the
University of Florida. While studying plant response
to different compost applications and irrigation rates,
the staff, who had a background in nematology,
noted the unexpected results while conducting rou-
tine observations. "Where compost was used, even
without a fumigant, there was a significant reduction
in rootknot nematodes," said Dr. Bryan.
Later research by Dr. Tom Obreza, a soil and
water scientist at Southwest Florida Research and
Education Center, turned up similar results. Dr.
Obreza's experiment consisted of growing tomatoes
in composts from several different sources and com-
paring them to control plots treated with the usual
Biopesticides (Tailored Compost)
Biopesticides are becoming effective alternatives
to chemical pesticides. Biopesticides are made by
adding controlled amounts of pest-fighting micro-
organisms to compost, which results in "tailored"
compost with a specific pesticidal capability. Biopesti-
cides must be registered with the U.S. Environmental
Protection Agency (EPA) and undergo the same
level of testing as chemical pesticides to determine
their effectiveness and their safety for public health
and the environment. Although one type of tailored
compost that is inoculated by a patented process is
already registered as a biopesticide with EPA, many
more are expected to follow suit.
&EPA
United States
Environmental Protection Agency
(5306W)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
fertilizers. Dr. Obreza found no disease problems in
any of the plots except one. Dr. Obreza noted, "We
had a little invasion of rootknot nematode in one
corner of the field. The infection was evident in the
plants right up to the compost treated plots and
stopped right there. The difference was as plain as
night and day."
References
Hoitink, H.A.J., and P.C. Fahy. 1986. Basics for the con-
trol of soil-borne plant pathogens with composts.
Annual Review of Phytopathology 24: 93-114.
Hoitink, H.A.J., Y. Inbar, and M. J. Boehrn. 1991.
Compost can suppress soil-borne diseases in container
media. American Nurseryman. September: 91-94.
Hoitink, H.A.J. 1990. Production of disease suppressive
compost and container media, and microorganisms
culture for use therein. U.S. Patent 4,960,348.
Marvil, J., J. Pinochet, and R. Rodriguez-Kabana. 1997.
Agricultural and municipal composts residues for con-
trol of root-knot nematodes in tomato and peppers.
Compost and Utilization 5(1): 6-15.
For More Information
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