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Larry Bass,
T.E. Bilderback
Gardeners have
used compost for centuries. When materials such as leaves and grass
clippings are composted, a microbial process converts plant wastes
to a more usable organic amendment. Grass clippings and leaves can
be hauled to municipal or county composting facilities as one means
of disposal. However, many homeowners may find it more convenient
and economical to compost these materials in their own backyards.
In either case, the finished compost can be used as a soil amendment
or mulch to improve most soils for gardens, landscape beds, lawn
preparation or even as 15% of a potting medium. This leaflet has
been written to provide guidelines on how to build and maintain
a compost pile. decomposition of organic material in the compost
pile is dependent on maintaining microbial activity. Any factor
which slows or halts microbial growth will also impede the composting
process. Efficient decomposition will occur if the following factors
are used to fullest advantage.
AERATION:
Oxygen is required
for microbes to efficiently decompose the organic wastes. Some decomposition
will occur in the absence of oxygen (anaerobic conditions); however,
the process is slow and foul odors may develop. Because of the odor
problem, composting without oxygen is not recommended in a residential
setting unless the process is conducted in a fully closed system.
Turning the pile once or twice a month will provide the necessary
oxygen and significantly hasten the composting process. A pile that
is not mixed may take three to four times longer before it can be
used. A well mixed compost pile will also reach higher temperatures
which will help destroy weed seeds and pathogens.
MOISTURE:
Adequate moisture
is essential for microbial activity. A dry compost pile will not
decompose efficiently. If rainfall is limited, it will be necessary
to water the pile periodically to maintain a steady decomposition
rate. Enough water should be added to completely moisten the pile,
but overwatering should be avoided. Excess water can lead to anaerobic
conditions. Water the pile so that it is damp, but does not remain
soggy. The compost will be within the right moisture range if a
few drops of water can be squeezed from a handful of material. If
no water can be squeezed out, the material is too dry. If water
gushes from your hand, it is too wet.
PARTICLE
SIZE:
The smaller
the size of organic wastes, the faster the compost will be ready
for use. Smaller particles have much more surface area that can
be attacked by microbes. A shredder can be used before putting material
in the pile, and is essential if brush or sticks are to be composted.
A low cost method of reducing the size of fallen tree leaves is
to mow the lawn before raking or run the lawn mower over leaf piles
after raking. Raked piles should be checked to insure that they
do not contain sticks or rocks which could cause injury during operation
of the mower. If the mower has an appropriate bag attachment, the
shredded leaves can be collected directly. In dition to speeding
up the composting process, shredding will initially reduce the volume
of the compost pile.
FERTILIZER
AND LIME:
Microbial activity
is affected by the carbon to nitrogen ratio of the organic waste.
Because micocrobes require a certain amount of nitrogen for their
own metabolism and growth, a shortage of nitrogen will slow down
the composting process considerably. Materials high in carbon relative
to nitrogen such as straw or sawdust will decompose very slowly
unless nitrogen fertilizer is added. Tree leaves are higher in nitrogen
than straw or sawdust but decomposition of leaves would still benefit
from an addition of nitrogen fertilizer or components high in nitrogen.
Grass clippings are generally high in nitrogen and when mixed properly
with leaves will enhance decomposition. Poultry litter, manure or
blood meal can be used as organic sources of nitrogen. Otherwise,
a fertilizer with a high nitrogen analysis (10-30%) should be used.
Other nutrients such as phosphorus and potassium are usually present
in adequate amounts for decomposition.
During the initial
states of decomposition organic acids are produced, creasing the
pH. In the past, small amounts of lime have been suggested for maintaining
and enhancing microbial activity at this time. However, high rates
of lime will convert ammonium nitrogen to ammonia gas which will
lead to the loss of nitrogen from the pile. Research indicated that
lime additions may hasten decomposition; however, the loss of nitrogen
from the pile often offsets the benefits of lime. In general, lime
is not necessary for degradation of most yard wastes. The pH of
finished compost is usually alkaline (pH = 7.1-7.5) without the
addition of lime. If large quantities of pine needles, pine bark,
or vegetable and fruit wastes are composted, additional lime may
be necessary.
Many organic
materials are suitable for composting. Yard wastes, such as leaves,
grass clippings, straw, and non woody plant trimmings composted.
Leaves are the dominant organic waste in most backyard compost piles.
Grass clippings can be composted; however, with proper lawn management,
clippings do not need to be removed from the lawn If clippings are
used, it is advisable to mix them with other yard wastes, otherwise
the grass clippings may compact and restrict airflow. Branches and
twigs greater than 1/4 inch in diameter should be put through a
shredder/chipper. Kitchen wastes such as vegetable scraps, coffee
grounds, and eggshells may also be added.
Sawdust may
be added in moderate amounts if additional nitrogen is applied.
Approximately 1 lb. of actual nitrogen (6 cups of ammonium nitrate)
is required for 100 lbs. of dry sawdust. Wood ashes act as a lime
source and if used should only be added in small amounts (no more
than 1 cup per bushel or 10 pounds per ton of compost). Ordinary
black and white newspaper can be composted; however, the nitrogen
content is low and will consequently slow down the rate of decomposition.
If paper is composted, it should not be more than 10% of the total
weight of the material in the compost pile.
Examples of
other organic materials that can be used to add nutrients to the
pile include: blood meal, bone meal, livestock manure, non-woody
clippings, vegetable and flower garden refuse, hay, straw and lake
plants. Livestock manure and poultry litter are nitrogen sources
for composting. Approximately 100 pounds of poultry litter will
provide 1.8 pounds of nitrogen.
Some materials
may pose a health hazard or create a nuisance and therefore should
not be used to make compost. Adding human or pet feces cannot be
recommended because they may transmit diseases. Meat, bones, grease,
whole eggs, and dairy products should not be added because they
can attract rodents to the site. Most plant disease organisms and
weed seeds are destroyed during the composting process when temperatures
in the center of the pile reach 150-160 F.
Although plants
that have been treated with herbicides or pesticides should be avoided
for composting, small amounts of herbicide-treated plants (e.g.,
grass clippings) may be mixed in the pile as long as one is careful
to allow thorough decomposition. Ideally, clippings from lawns recently
treated with herbicides should be left on the lawn to decompose.
Use of plastic
garbage bags is perhaps the simplest way to make compost. The bags
are easy to handle, and require minimal maintenance. To make compost
using this method, 30-40 gallon plastic bags should be alternatively
filled with plant wastes, fertilizer and lime. About one tablespoon
of a garden fertilizer with a high nitrogen content should be used
per bag. Lime (one cup per bag) helps counteract the extra acidity
caused by anaerobic composting. After filling, add about a quart
of water. Close tightly. Set aside for six months to a year. Bags
can be set in a basement or heated garage for better decomposition
during winter months. Using garbage bags requires no turning or
additional water after closing. The main advantage of composting
in garbage bags is that it requires little maintenance; however,
because oxygen is limited, the process is slow.
The barrel or
drum composter generates compost is a relatively short period of
time and provides an easy mechanism for turning. This method requires
a barrel of at least 55 gallons with a secure lid. Be sure that
the barrel was not used to store toxic chemicals. Drill 6-9 rows
of 1/2 inch holes over the length of the barrel to allow for air
circulation and drainage of excess moisture. Place the barrel upright
on blocks to allow bottom air circulation. Fill the barrel 3/4 full
with organic waste material and add about 1/4 cup of high (approximately
30%N) nitrogen containing fertilizer. Apply water until compost
is moist but not soggy.
Every few days,
turn the drum on its side and roll it around the yard to mix and
aerate the compost. The lid can be removed after turning to allow
for air penetration. Ideally, the compost should be ready in two
to four months. The barrel composter is an excellent choice for
the city dweller with a relatively small yard.
For larger quantities
of organic waste, bin type structures are the most practical. As
an example, a circular bin can be made by using a length of small
spaced woven wire fencing and holding it together with chain snaps.
The bin should be about three to five feet in diameter and at least
four feet high. A stake may be driven in the middle of the bin before
adding material to help maintain the shape of the pile and to facilitate
adding water. With this design, it is easiest to turn the composting
material by simply unsnapping the wire, moving the wire cylinder
a few feet, and turning the compost back into it.
A very efficient
and durable structure for fast composting is a three-chambered bin.
It holds a considerable amount of compost, and allows good air circulation.
The three chambered bin works on an assembly line idea, having three
batches of compost in varying stages of decomposition. The compost
material is started in the first bin and allowed to heat up for
three to five days. Next, it is turned into the middle bin for another
4-7 days, while a new batch of material is started in the first
bin. Finally, the material in the middle bin is turned into the
last bin as finished or nearly finished compost.
To make a three-chambered
bin, it is best to use rot resistant wood such as redwood, salt
treated wood or wood treated with an environmentally safe preservative
or a combination of treated wood and metal posts. Unless the wood
is treated or rot resistant, it will decompose within a few years.
Each bin should be at least three to five feet in each dimension
to contain enough volume to compost properly. Using removable slats
in the front offers complete access to the contents for turning.
The compost
pile should be located close to where it will be used and where
it will not interfere with activities in the yard or offend neighbors.
From the aesthetic point of view, it is best to compost in a location
screened from view of both your property and neighbor's operty.
Examples of good locations for the pile include: near the garden
or between the garage and house. Do not locate the compost pile
near a well or on a slope that drains to surface water such as a
stream or a pond. T pile will do best where it is protected from
drying winds and in partial sunlight to help heat the pile. The
more wind and sun the pile is exposed to, the more water it will
need. Locating the pile too close to trees may also create problems
as roots may grow into the bottom of the pile and make turning and
handling the compost difficult.
Organic wastes,
such as leaves, grass, and plant trimmings are put down in a layer
eight to ten inches deep. Coarser materials will decompose faster
if placed in the bottom layer. This layer should be watered until
moist, but not soggy. A nitrogen source should be placed on top
of this layer. Use one to two inches of livestock manure, or a nitrogen
fertilizer such as ammonium nitrate or ammonium sulfate at a rate
of one third of a cup for every twenty five square feet of surface
area. If these nitrogen sources are not available, one cup of 10-10-10
fertilizer per 25 square feet of surface area will also suffice.
Do not use fertilizer that contains herbicide or pesticide.
About a one
inch layer of soil or completed compost can be applied on top of
the fertilizer layer. One purpose of adding soil is to ensure that
the pile is inoculated with decomposing microbes. The use of soil
in a compost pile should be considered optional. In most cases,
organic yards wastes such as grass clippings or leaves contain enough
microorganisms on the surface to effect decomposition. Studies have
shown that there is no advantage in purchasing a compost starter
or inoculum. One way to insure that activator microbes are present
in the new compost is to mix in some old compost as the pile is
prepared.
Most compost
piles should initially be prepared in layers. This will facilitate
decomposition by insuring proper mixing. Each pile ideally should
be about 5 feet high. If only tree leaves are to be composted, layering
may not be necessary. Fallen leaves can be added as they are collected.
Leaves should be moistened if they are dry and since dead leaves
lack adequate nitrogen for rapid decomposition, addition of a high-nitrogen
fertilizer (10- 30% analysis) should be added to speed up breakdown.
Approximately 5 ounces (about 1/2 cup) of 10% nitrogen fertilizer
should be added for each 20 gallons of hand compressed leaves.
To prevent odors
and hasten decomposition, the pile must be turned occasionally.
Turning also exposes seeds, insect larvae, and pathogens to lethal
temperatures inside the pile. Odors may arise either from the addition
of excessive amounts of wet plant materials like fruits or grass
clippings, or from overwatering. A properly mixed and adequately
turned compost heap will not have objectionable odors. An actively
decomposing pile will reach temperatures of 130-160 F in the middle.
Reasons for
the pile not heating up may be due to: too small a pile, not enough
nitrogen, lack of oxygen, too much or not enough moisture. The pile
should be turned when the temperature in the center begins to cool.
This will introduce oxygen and undecomposed material into the center
and subsequently regenerate heating. The composting process is essentially
comple when mixing no longer produces heat in the pile.
Generally, a
well managed compost pile with shredded material under warm conditions
will be ready in about 2-4 months. A pile left unattended and material
not shredded may take over a year to decompose. Piles prepared in
the late fall will not be ready for use the following spring. When
the compost is finished, the pile will be about half its original
size and have an earthy smell to it.
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information contained on this web page is derived from industry
sources which are considered reliable. Information is subject to
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Copyright ©1995
- 1999 Barrington Multi Media., all rights reserved.
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