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University
of Rhode Island GreenShare Factsheets
Organic
Lawn Care
In the literal sense, organic is
defined as any compound containing carbon and, thus, includes
both natural as well
as synthetic sources. In the more familiar sense, organic implies
compounds which occur naturally. Rising concern for the environment
has led to an increase in the organic approach to lawn care.
In lawn care, organic care programs are based on maintenance
of a vigorous turf in an effort to minimize the need for major
inputs. In organic lawn care, the inputs that are necessary
tend to be " natural" as opposed to the synthetic ones used
in conventional programs. Consumer demand for "organic lawn
care" has resulted in the Ecological Landscape Association's
development of a program for standardization of organic lawn
care. The goal of organic lawn care is to use ecological options,
including such concepts as IPM and "least toxic pest management."
The underlying basis of organic lawn care practices is
the management of a soil in which the biotic character is preserved.
Organic matter provides nutrients, moisture retention, texture,
and an environment to sustain high populations of microorganisms.
Fertile soil is essential for a healthy lawn. A soil
test is a fundamental first step to any organic or conventional
lawn care program. The two programs differ mostly in the forms
in which nutrients are added.
Sources of nitrogen in organic
fertilizers include bone meal, dried blood, vegetable and
feather meals, manures and
sludge, and may range from 3-10% by weight. In this form, most
of the nitrogen is bound to complex organic molecules and is
inaccessible to plants until it is slowly released, over time,
by the natural activity of soil microorganisms. Organic nitrogen
sources permitted include such materials as composted manures,
cover crops, and green manures. In contrast to fertilizers
which release nitrogen immediately and produce a rapid "green-up," response
of grass to organic fertilizers may take months to years. In
addition, nutrient availability may be limited during cold
periods when microorganism activity is minimal. The typical
slow response time and high cost associated with the use of
organic products has led to an increase in the sales of fertilizers
which contain mixtures of natural/synthetic and natural/inorganic
nutrient sources. While use of these products reduces green-up
time and cost, they are not in compliance with "natural organic" standards.
Natural organic fertilizers, as
well as composts and manures, are excellent providers of
other essential nutrients.
Sources of phosphate include bone meal (derived from vertebrate
skeletons) and rock phosphate. The first may contain an odor
and may be difficult to spread. The latter is effective only
if acid treated to break down particles to a more available
form, a practice not accepted by organic certifying groups.
Low levels of potassium are found in most composts. Potassium
may also be provided by wood ash or as potassium sulfate. In
addition, humates, or "biostimulants," are sold to provide
nutrients for turf. Given a proper pH (approximately 6.5),
other nutrients are also available in most sources of composts
or can be supplemented in their "natural" form.
Maintenance of a vigorous lawn depends upon cultural
practices to increase the diversity and health of beneficial
organisms in all levels of the soil. The ecological lawn seed
mix should thus be comprised of a variety of grass species
and cultivars in order to take advantage of the disease-resistance
qualities of each and to reduce susceptibility to damage by
pests specific to any one.
Endophyte-infected grass mixtures, which
are combinations of specific cultivars of tall fescue, perennial
ryegrass and
fine fescues, are currently being marketed for sustainable,
organic lawn care situations. The beneficial symbiotic relationship
between the plant and a fungus that lives inside of it results
in grasses which tend to be more vigorous than endophyte-free
varieties under a range of cultural conditions and when under
abiotic stresses such as drought, heat, and low nutrients.
Also, endophyte-infected grasses have resistance to foliar
feeding insects such as chinch bugs, billbugs and sod webworms.
For more information, see GreenShare
factsheet on endophyte-enhanced grasses.
The IPM strategy for organic lawn
care is prevention. The aim is to use plant selection, establishment
and maintenance
practices to promote, conserve and enhance natural pest controls.
A healthy, well-rooted turf can compete with many species of
weeds. Mowing high is another organic strategy aimed at shading
out particularly troublesome annual weeds as crabgrass, which
require light to germinate. The presence of weeds is used as
an indicator of other cultural problems, such as nutrient deficiencies
or compaction, which may then be corrected. In addition, organic
lawn care endorses the need for education aimed at acceptance
of a certain level of "weeds."
Disease management also focuses on providing
optimal conditions to maintain the health of the grass and
soil. Good drainage
and proper soil pH contribute to the conservation of organisms
antagonistic to pathogens. Practices such as establishment
of disease-resistant grasses, increasing air circulation and
avoiding watering at times when the grass will remain wet may
all be used in attempts to prevent disease. Natural and/or
organic supplements may also be used to change an environment
which favors the disease organism. Certain composts are disease-suppressive,
although the particular organisms involved have yet to be identified.
Some specific natural organic fertilizers have also been found
to suppress specific diseases such as dollar
spot, brown patch and red
thread.
An organic approach to pest management
for insects focuses on "least toxic control strategies." Avoidance of broad spectrum
pesticides which affect "nontarget" organisms results in the
maintenance of natural pests. Biological controls such as predators
and parasites can also be used in addition to natural organic
sprays and dusts. As mentioned previously, endophyte-infected
grasses are resistant to a number of surface-feeding insects.
Entomophagous ("insect-eating") nematodes such as Steinernema
carpocapsae parasitize the larvae of sod webworms and cutworms.
Bacteria such as B.t. (Bacillus thuringiensis) can be
used against the sod webworm and
the cutworm as well. Botanical
insecticides as rotenone and pyrethrum are also allowed
as part of an organic pest control program. Emphasis on scouting
and spot treatment reduces costs and overuse of even these
more ecologically sound methods of organic pest control.
Adapted from the Unniversity
of Massachusetts Extension, 1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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