Good composting can be
likened to good cooking, and the same four basics apply :-
- Use only good quality
- Prepare your ingredients
- Follow the recipe
- Decide on the cooking method
Most of your garden waste is good for composting with. The
exception would be oxalis, and other invasive, root propagating
weeds. Don't necessarily exclude other weeds such as Kikuyu grass,
Gorse, Wandering Jew etc as they are an excellent (and prolific)
source of composting material. With these noxious weeds special
care needs to be taken with adequate shredding and a composting
system that has a high heat build up. Never include meat, fat, or
bones in your compost but fresh kitchen scraps are excellent.
Trying to compost without a shredder is like a chef without a mix-master.
Inadequate preparation would be the most common cause of failure
in composting. Here are some guides in your search for a suitable
shredder for you -
Disregard performance figures given
by manufacturers - in our experience, if used continuously to the
sizes stated, the shredder will not last.
Most electric shredders take a maximum of 25mm and petrol powered
35 to 45mm. 90% of your garden waste volume comes from material
smaller than 19mm.
Cheap electric shredders ($399ish),
for other than very small gardens, are a waste of money. You need
to spend $600 or more. Germans produce the best designed and
Petrol shredders that have the
cutting blade mounted directly on the engine crankshaft have a
habit of breaking shafts (despite claims of toughened crankshafts
that the engine manufacturers haven't heard of). Some have an
extra support bearing that makes them tolerable but belt drive is
The best composting material comes
from a flail and screen shredder - different screens accommodate
wet and difficult materials. Australian and NZ manufactured petrol
shredders are the best in the $1000 to $2000 price bracket.
Different shredders are better for
different kinds of garden - to get the right one for your garden,
buy from a shredder specialist who knows his product and is
prepared to demonstrate.
You don't put a bag of flour and a pint of milk in the oven and
hope to get scones! Read the section on recipes.
Different systems suit different gardens - let us guide you. The
850 watt microwave of composting systems is the Suttons 400
Compostumbler. Providing that you have sufficient lawn clippings
and shredded garden waste to feed it - it will produce three
contractors barrows of very rich melior compost every two weeks.
At Gardening Aids Limited we have
the garden machinery and garden tools to change your garden chores
into a pleasure.
Gardening Aids Limited
Composting vegetation can be
likened to cooking food. In composting we are making nutrition for
our plants, just as we are supplying nutrients to our bodies with
our cooked food. The ultimate nutritional value of compost, just
like our food, is dependant on the correct recipe in the first
place, "cooked in the most efficient way, in the shortest
possible time. Secondary considerations are ease of operation,
hygiene, quantity and type of material able to be processed. One
method of composting alone does not necessarily suit all people.
The choice of method has to take into consideration the volume,
type of material, and ultimate use of compost. Composting benefits
from attention to the recipe and the preparation of material.
nutritional value of compost is dependant on the material
in it and the speed with which it reaches maturity.
Successful composting is
dependant upon these four points:-
correct balance of ingredients
preparation of material (wood
and large leaf material should be shredded)
the moisture content ( should be
damp not sodden)
Traditionally, composting was done
by the Indore or Berkley method which was both back breaking and
time consuming. Today there are several types of bins to choose
from and at Gardening Aids Ltd we are able to offer you a full
range to cover your expectations.
Its important to remember when choosing your method of composting
that a good technique ensures minimal losses of nutrients and
hence their maximum return to the soil. Composting is just a
method of speeding up the natural process so that we can
capitalise on the nutrients for our gardens.
The Ratios In
Compost of high fertiliser value can only come from high
quality” rubbish. The most important aspect here is the carbon
nitrogen (c/n) ratio of the organic materials used.
Micro-organisms need both carbon and nitrogen to make protein. As
they use about 30 parts by weight of carbon for each part of
nitrogen used, we need to supply them with materials having a c/n
ratio of about 30. Microbial activity is reduced at higher c/n
ratios (low nitrogen supply) and valuable nitrogen may be lost as
ammonia gas if the c/n ratio is lower than about 30. In practise,
it has been found that the average c/n ratio of the materials in a
compost heap should be slightly less than this - in the range 25
to 30 - for the heap to work”. The table will help you achieve
somewhere near the optimum c/n ratio. Further mixtures may be
formulated according to the materials available. Provided the c/n
ratio is right, it is not essential that animal manures are
included. Micro-organisms also need abundant supplies of the other
nutrient elements, with phosphorous being particularly important.
A carbon/phosphorous (c/p) ratio in the range 75 to 150 is needed.
Leaves, (especially gum leaves), woody plant residues, and
sometimes even lawn clippings ,have c/p ratios above 150. In these
situations it is desirable to add more phosphorous to most compost
heaps so as to ensure rapid decomposition. Superphosphate can be
used, but if a more natural source of phosphorous is preferred,
use bone meal or rock phosphate. Use only light sprinklings as
more than about 2% by weight can inhibit decomposition. The other
nutrients needed by micro-organisms are usually present in
sufficient amounts if a wide range of organic materials is used.
The moisture content of a compost heap is very important.
Below about 40% moisture (40g water in 100g moist materials; ie.
40g water + 60g dry matter), organic matter will not decompose
rapidly. Over about 60% moisture not enough air can get into the
heap and it tends to become anaerobic (no oxygen). It is best,
therefore, to aim at 50 to 55% moisture. This is likened to the
moisture of a squeezed sponge.
To Lime or Not
Initially the pH of a compost heap is slightly acidic because
the cell sap of plants is acidic. Then the heap becomes even more
acidic, due to acids such as acetic, sulphuric, nitric, etc.,
produced by bacteria. During the thermophilic stage it becomes
alkaline through ammonia formation, and finally, near neutral, as
the ammonia is absorbed by the acids to form ammonium sulphate,
ammonium nitrate, etc. The addition of lime to compost inhibits
the absorption of ammonia and can lead to serious nitrogen loss.
In a well ventilated compost system, ie. a Compostumbler, no lime
is required. In the plastic bin type, because of its inherent
tendency to become anaerobic, and therefore excessively acidic,
lime must be added.
Published recipes state that alternate layers of high nitrogen
and low nitrogen materials should be built up on top of one
another into a heap about 1.5mtr high. Local experience suggests
that it does not matter much whether the materials are layered or
mixed up before hand, so long as the C/N ratio is near the optimum
of 25 to 30. To work, the heap needs to be at least one or two
cubic metres in volume. Frequent turning for adequate aeration is
the secret for successful composting. Providing the heap is turned
every two to three days, it should be ready for use in three to
four weeks. Because of the size required, this method is not
really suitable for suburban gardens.
This method involves
minimum effort, but it takes a long time to produce a usable
product. Alternate layers of low nitrogen and high nitrogen
materials are heaped on top of one another to a height of about
1.5mtr. The heap should be about 2mtr square at the bottom,
tapering to about 1.5mtr if it is free standing. The heap is
covered with a 5cm layer of compacted soil to deter flies and to
prevent the escape of foul odours. If the heap is turned, the
first turning should be eight to ten days after making, then after
a further thirty or forty days. The process of decomposition takes
a year if the heap is never turned.
The previous methods are
more suitable for semi-commercial or rural situations. Most urban
gardens would use some form of compost bin, the most common being
the three bin method made of wood or other material where
materials are laid down similarly to the Berkeley method but
turned from one bin to the next in rotation. There are a large
number of proprietary plastic compost bins available, which would,
with care produce compost. However, the danger with this kind of
bin, is that the heap” will revert to an aerobic decomposition,
with its associated smells and low nutritional value of the end
product. The most successful of all compost bins is the Sutton's
Compostumbler which can produce high nutrient compost within 14
days. No flies, no smell, no mice or rats, and little effort.
Do You Really Need Them?
Some hundreds of species of
micro-organisms, mostly bacteria, fungi and actinomycetes
(branching bacteria), are involved in decomposing organic
materials. Most organic materials have a native population of
micro- organisms and others are added to a compost heap in the
garden soil often mixed into or layered amongst the organic
materials. These micro-organisms start their work of decomposition
as soon as moisture and oxygen concentrations are favourable. Many
research studies have shown that special preparations of fungi,
bacteria or enzymes” are not needed for rapid decomposition;
there are plenty of organisms in the materials commonly used to
make compost. Only where sawdust (or other relatively sterile
materials) form a high proportion of the heap is inoculation not a
waste of money. The claimed advantages of some commercial
preparations are often due to the extra nitrogen and other
nutrients they supply rather than to the micro-organisms they
contain. These nutrients can be bought much more cheaply in
fertilisers. If in doubt, add a small amount of mature compost to
each new heap.
Grinding or chopping up the
organic material speeds decomposition by increasing the surface
area available to micro-organisms. There are available, today, a
wide range of inexpensive garden shredders, either petrol or
electric powered, to suit your needs. These shredders will turn
your garden waste and prunings into an easily compostable mulch.
Your lawnmower will supply
you with a continuous supply of moist bulk material for your
compost. Lawn clippings are especially valuable, when mixed with
either peat or untreated sawdust, in tumbler type composters. To
keep work to a minimum choose a lawnmower that has a catcher.
Hover or side delivery mowers can create a lot of unnecessary work
if you are intending to compost. Mulch mowers are very little
benefit too if you are wanting to use the clippings. Should you be
contemplating a ride on type mower be sure to choose a machine
that has already got the chute-catcher attached to it as generally
these machines are more efficient.
Blowers / Vacuum
The outdoor vac is designed
to capture all those elusive autumn leaves from gardens beds,
under shrubbery, and those awkward corners. Naturally they are
great for lawns, driveways and gutters. Blower vacs come in many
shapes and form. There are hand held machines as well as
on-the-ground-push type. Both are available in electric as well as
the freedom loving petrol variety. Apart from their comfort and
mobility check out their ability to shred. Some vacs are so
efficient at shredding you can simply empty your vac bag straight
into your compost.
There are many labour saving products available on the market
today to increase your productivity and reduce stress. Check out
the Gubba range of product from the handy carry bags to garden