BEGINNERS' GUIDE TO
Compost and Worms
“If it has lived, it can live again”
Very Edible Gardens PTY LTD
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Benefits of compost
Compost. What else can turn the dead back into living, thriving
plants? What else turns rubbish into the gardeners' 'black
Compost is a natural soil improver made from broken-down
organic matter, and it contains three things of vital importance
• humus (that's the dark spongy material that makes good
soil the colour of chocolate)
• recycled nutrients
• billions of microscopic lifeforms which create a healthy
Healthy soil creates healthy plants, which creates healthy humans. And to this end, composting is
our most important tool. It really is the cornerstone of organic gardening. Some of the benefits of
• In clay soils, it improves drainage and nutrient availability.
• In sandy soils, it improves water and nutrient holding capacity.
• In both acidic and alkaline soils, it helps neutralise pH!
• Many toxins are broken down in the composting process, while others such as heavy
metals in city soils become locked up and less available to plants when compost is added.
Since up to two thirds of household waste is compostable, it's a great way to divert waste that
otherwise creates methane in landfill.
Not any pile of rotting vegetables is really compost. Compost should smell great, like a rainforest,
and that's how you'll get the best product for your garden too. To get there, there are some simple
rules to follow.
Both your soil and your compost pile are literally alive with worms, bugs and microbes. (And yes,
that's a good thing, without them there would be no compost.) Like us, they need the basics: food,
water, air, and shelter. We'll explain how to make great compost using these principles.
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Types of compost
There are many different ways to make good compost, and these include:
If you pile organic left-overs and garden clippings into a really big pile – at least one cubic metre –
the pile will usually generate enough heat to kill weed seeds and most diseases in the middle.
Hot composts are “batch processes” – that is, you need to gather all your ingredients at the
beginning and kick start the process all at once. You do need to turn hot composts to make sure
the cooler outside of the pile is cycled at least once, through the hot hot centre. Hot composts need
to get to 55°C for about three days to kill weed seeds and pathogens, but usually they will get even
hotter – hot enough to cook an egg! Hot composting is the fastest way of making compost – in as
little as three weeks. You might build a hot compost if you are kick starting a new garden, or if
you have a big block of land with lots of weeds on it that you can harvest all at once. It's often
possible to get lawn mowing companies to deliver clippings to you for free which can be a good
excuse to create a hot compost. Hot composts are often one for the real enthusiasts, so we'll focus
on the other strategies and you can search the internet for the 'Berkley Method' of hot composting
if you'd like to learn more.
Usually what we're talking about here is compost in plastic bins. Most
of us home composters place our kitchen scraps, and sometimes garden
weeds and prunings, a little bit at a time, into a medium-sized compost
bin. Although it warms up a bit, the compost never gets particularly hot
this way, so we'll call this method the cold composting method.
Although it doesn't kill weed seeds (so you need to do your weeding
before the weeds produce seed) you don't need to start it all at once,
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which is more practical for daily needs. This is a perfectly fine and decent way of making
compost, however you do need to follow our advice below to make a good product. You'll also
need (at least) two bins so that one rests, once the other is filling.
One of the things we love to do in our gardens is harness the power of
the chook to do the garden chores for us. One way of harnessing this
power is to make compost, and in the process we can offer them a
better life. We do this in what we call a strawyard. Chickens love to
scratch and eat food scraps and bugs. If you put chickens on top of a
thick layer of straw and throw in food scraps, they'll turn and mix the
compost looking for bugs, while the straw absorbs the smell of the
chook poo. We don't cover this method in this course, but there's some
info on the www.VeryEdibleGardens.com website (in the iVEG section) or you can come along to
one of our Power of Chook workshops.
Compost worms are well suited for most kitchen scraps, but not woody garden materials. They
produce a wonderful compost and we'll deal with worms in a separate section below.
So now, lets talk about food, water, air and shelter.
Food: A Balanced Diet
You don't need a food pyramid to figure out what your compost needs, you just need to know
about two basic categories:
• carbon-rich, and
• nitrogen-rich materials.
Your compost needs a good balance of each, so we talk about carbon-to-nitrogen ratios. That may
sound complex, but it's not really. In fact it's very intuitive! Of course in both cases we're talking
about things that were once alive – anything made of organic materials.
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In general, carbon-rich materials tend to be brownish, often dry, and don't rot easily. How do you
know something is high carbon? Imagine it in a bucket, covering it with water, and coming back
two weeks later. If it hasn't broken down much and hasn't begun to stink much, it's high in carbon.
Sawdust and newspaper are examples of materials that are very carbon-rich.
High nitrogen materials tend to rot – and stink – readily. Any green foliage is relatively high in
nitrogen. If you were to repeat the bucket experiment with them you would discover that they do
stink when left in water for a couple of weeks. Try it with fish guts and you'd discover that they
are very nitrogen-rich.
High-carbon materials take a long time to break down and don't
produce strong smells
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High carbon materials absorb odours, and prevent the loss of nutrients, and slow the breakdown
process. Mixing high-carbon and high-nitrogen materials gives you the right balance.
Using around 2 parts Carbon-rich materials to 1 part Nitrogen-rich material (by volume) from the
table below will be about right. For example, you could mix two buckets of loose straw to one
bucket of kitchen scraps. Or two buckets of autumn leaves to one cup of chicken manure.
Carbon-rich materials (1 part = 1 bucket)
Wood shavings and sawdust
(Woodchips are carbon-rich but usually too
chunky to be of use)
Nitrogen-rich materials (1 part = 1 bucket)
Green lawn clippings & weeds
Manure (eg. cow, horse, sheep)
Wool, feathers, hair
Extremely nitrogen-rich (1 part = 1 cup)
Blood and bone
It's useful therefore to have a pile of straw or autumn leaves, or a bin containing water and ripped
High-nitrogen materials rot quickly and produce foul smells if not
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cardboard, next to your compost pile, and add some carbon every time you add green weeds and
kitchen scraps. If this sounds all too much, don't worry too much about ratios – if your main
input is kitchen waste, just adding any amount of carbon at all will improve things.
The smaller the size of the ingredients the better they'll mix, and the faster your pile will break
down. We use a sharp spade to bruise and cut weeds before putting them in the compost.
Build your compost in layers, always finishing with a layer of carbon to absorb smells.
What should I and shouldn't I put in the compost?
Large amounts of citrus or onions aren't good for worms and can slow down other
Excessive amounts of meat or dairy: don't add any of these unless you have a healthy,
quickly breaking-down system, and bury them deep inside the pile to avoid flies.
Dog and cat poo can be worm composted or hot composted, but kept in separate systems
and shouldn't be used on vegie beds. Some parasites can survive worm composting,
although hot composting should kill everything.
Some plant diseases and weed seeds may survive cold composting so avoid diseased plant
matter and weeds gone to seed.
Eucalyptus leaves and pine needles should be stored separately for a few months until they
lose their strong smell.
Wood ash? A bit is ok, it is rich in nutrients, but if left in the rain becomes very alkaline.
Never burn treated pine or use its ash in the compost!
Some twigs and branches can be great to help aerate the pile.
Coffee grounds and tea bags are excellent ingredients – go for it!
Cardboard, newspapers, pizza boxes – for sure! Just wet and rip them up first, and avoid
the glue in cardboard boxes. Newspaper ink is made from soy and is compostable.
Glossy coloured magazine paper is a bit suspect, even though the shine itself is simply a
clay coating, the inks may be more toxic. Probably best to avoid it.
Eggshells, avocado seeds, mango seeds and some other things all take a long time to break
down, but will eventually. Crush eggshells.
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Some plants are so called 'dynamic accumulators' – they concentrate nutrients from the soil and
help 'activate' and speed up the compost process. They aren't essential, but it can help to add the
leaves of yarrow, tansy, comfrey, nettles or chamomile to your compost pile.
It is important to keep the pile moist. Soak cardboard or straw before adding and/or water each
layer. But don't saturate the pile. It should be 50% moisture – you know it's right moisture level
when you squeeze a handful between your fingers and a drop or two comes out between your
fingers, but no more.
You can aerate your compost by either:
(a) For hot composts: turning it from one place to another, and moving
what was on the outside to the inside of the pile. A pitchfork is the
best tool for doing this with.
(b) For compost bins ('cold' compost): Some of the plastic compost bins
have no aeration. If yours is like this, you need to drill lots of holes
into it! Make the holes small enough that flies don't get in. Around
60 or 100 holes would be a good number. A truly useful tool for
mixing and aerating your compost is a compost screw.
Turning mixes the ingredients, aerates and speeds up the composting process. If you turn twice a
week, you will have beautiful rich compost in 3 weeks to 2 months for a hot compost, or more like
3-5 months for a cold compost, depending on the weather and your ingredients.
If your compost is not in a plastic bin, keep your compost pile out of direct summer sun and hot
winds so it doesn't dry out. You will want to protect it from too much winter rain so it doesn't get
soggy. You can put your compost pile under the canopy of a tree, or if it's not in a compost bin,
you can use a tarpaulin – just make sure some air can get underneath.
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Is your compost too stinky? It may be too wet, or too nitrogenous. If it looks too wet and is
stinky, mix in dry carbon-rich material, aerating well. If it doesn't look too wet, mix in soaked
carbon-rich material. Make sure it is well aerated. Consider mixing in some twigs, and drill holes
in plastic bins if you haven't already.
Is your compost not breaking down quickly? It may be too dry or too carbonous. Mix in
nitrogen-rich material, and water if it looks dry.
Mice or rats? If you have problems with mice or rats getting into the compost, you may need to
bury the base of your compost bin in the ground, or put bird net wire underneath the bin.
Worms produce perhaps the very best and richest compost for the vegie garden, and worms are
especially suited to dealing with kitchen scraps. Worms speed up the composting process,
introduce excellent microbiology for your soil, and aerate and mix the compost ingredients for
you. Like other forms of compost we need to consider a balanced diet, water, air and shelter.
Compost worms are not the same as garden earthworms – they live closer to the surface, prefer
wetter conditions and eat ‘raw’ organic material. Compost worms will only survive in your
garden if there's lots and lots of organic material for them.
How many worms should I start with? We recommend that you start with 1,000 multiplied by the
number of people in your house. A well maintained worm farm will increase its population to a
comfortable amount for the space and food provided. Worms can double in numbers every two
months or so, and may breed up to as many as 20,000 in
one of the small commercial worm farms.
Can-O-Worms worm farms are a great house for a
thriving worm farm, except they MUST be kept in a
cool spot on hot days such as a garage or worms will
die. They come with instructions on how to use the
multi-tray system, which is very efficient and allows
you to harvest the compost while leaving the worms
behind. Extra tips: If some stubborn worms won't leave
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the bottom tray come harvest time, put that tray on top and keep the lid off for several hours
during the day. The light will encourage the remaining worms down into the active tray. If worms
congregate in the bottom of the bin (the worm-juice collecting part) you can drill a few small holes
in that area. The light discourages them from coming down there and helps aerate the worm
liquid so it doesn't begin to stink.
Polystyrene box: If you’re budget conscious, you can
make your own worm farm with three stackable
polystyrene boxes that have holes in the bottom. This
will need to be standing on a large tray to catch the
worm juice, and should be covered with a wet hessian
bag or a waterproof cover if your farm is exposed to
rain. The insulating properties mean that these survive
hot weather better, but they don't keep out mice or flies.
Other systems: Worm farms don't need to have the
multiple box system. You can make or buy worm farms
made from recycled plastic, wheelie bins or wood which
you fill from the top, and harvest from the bottom. You can also keep worms in a bathtub as long
as there is good drainage. The more surface area, the more you can feed them.
To start your worm farm, add the following:
1. A few cm layer of coconut fibre, dry grass clippings, wet straw or wet cardboard
2. Your worms mixed with a good amount of compost (which they should come with)
3. Worm food (see below)
4. Cover with a thick layer of damp newspaper, a wet doormat or hessian
Where should I put my worm farm?
A well maintained worm farm will not smell or attract pests, and worms need a sheltered, shady
spot that isn’t too light or hot. It’s best to place it near your kitchen for easy access. (Eg. in the
laundry, the shed, on a balcony, or under a tree). Protect them from any direct summer sun, but
sun will help in the winter.
Food for worms
Worms like fruit and vegetable kitchen scraps (and the older and softer the better), soft weeds, tea
bags. They love pumpkin, coffee grounds, manures and wet cardboard! Go on, give your worms a
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treat. Add wet shredded cardboard or wet straw each time that you feed the worms to keep the
worm farm smelling sweet, (adjusting the old C:N ratio). To increase the fertility of your worm
castings, it is important to give your worms a varied diet.
Worms don't like citrus, onion, or too much oil, meat or dairy. Too much bread can go mouldy and
they don't eat it. They don't have teeth, so they can't handle anything woody.
Feed your worms only so much as they can eat. They should turn whatever you put in into
compost within a week or two, otherwise it's too much food. Start slowly and add more as their
numbers build up.
The final product should look dark and rich (about like 70% cocoa chocolate). You can use it when
there are still some not-quite completely broken down bits and it's not completely uniform, but it
should be almost entirely the dark colour.
Sour smell and lots of tiny vinegar flies: add wet shredded newspaper or straw. Bury new food
under existing castings.
Ants: something sweet is in the compost, or is too dry. Remove sweets, or add water.
It’s normal to have slaters, mites and a few vinegar flies and other creatures in the worm farm.
Other creatures in the worm farm: The tiny white creatures called springtails, tiny brown mites,
slaters, earwigs and other creatures can all help with the breakdown process. Don't worry about
Good books: Organic Growing with Worms by David Murphy (available through VEG)
Using the compost!
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When starting a new garden in bad soil you might gently mix your
compost into the top 15cm of soil. After that, it's good to simply
place it on top, but under a layer of mulch. Compost creates fluffy,
living, humus-rich soil. You must keep it moist, out of direct
sunlight and hot winds. Mulch provides shelter, holds moisture and
is itself food for the soil as it breaks down. Don't step on it, or use
artificial chemicals. Use straw mulches for veggies, wood chips for
trees and shrubs.
Organise your garden beds so that you don't need to walk on them to harvest your veggies. And
you will have turned waste into healthy living soil, healthy plants and healthy you!