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One of the great things about growing your own food at home, is that you can recycle much of your own food waste and other organic waste (like weeds, grass clippings etc) and turn them back into fertiliser for your garden. Two of the best ways to do this at a domestic scale is composting and worm farming. 


Composting is a key aspect of successful organic veggie gardening. It turns bulk organic materials back into a usable soil ingredient. In a forest, bird and animal manures mix with leaves and twigs on the 'micro organism rich' forest floor. Broken branches and dead creatures are broken down relatively quickly in such a rich living system. Applying compost to your soil is replicating this natural process.


Adding compost back into your garden is required for maintaining good nutrient levels in the soil, and it also improves the structure of the soil layer, increasing both drainage and moisture retention. Not to mention that composting makes the most of every scrap of left over 'waste' materials from your garden and kitchen.



Before you begin making compost, you need to find a good spot and set up one or more compost bins. There are a few different options, such as a two or three bin system made from wooden planks (or if you can find some old untreated forklift pallets, nail 4 of them together in a square for a quick compost bin), a store bought black plastic bin, etc. 

If you prefer, you can simply make a compost heap that is not contained. This is better suited to larger volumes of material (greater than one cubic meter) such as if you have done a lot of yard work and have lots of hedge trimmings, grass clippings etc. 



It's all about ratios... 


One of the most important ratios to get right, the balance of carbon to nitrogen dictates whether your compost will turn into rich black earth, a stinky slimy mess, or just sit there looking at you. Basically carbon provides the bulk matter for humus (the good black stuff that we are aiming to make when we compost) and nitrogen provides the fuel for the bacteria and microorganisms that do all the work. Not enough nitrogen in the mix and no matter how long you leave your heap it will still be full of untouched dry material. Too much nitrogen on the other hand leaves your compost looking and smelling like something evil...


BROWNS - carbon rich, dry
Browns are those that you could burn if left to dry out, they also help air flow and drainage of moisture.
Always start with a double layer of coarse browns for aeration and always build it directly on the ground.

  • torn up newspaper/cardboard, unbleached and unglossy paper

  • egg cartons

  • tree prunings

  • dry leaves

  • bark, untreated sawdust

  • wood ash

  • twigs and sticks

  • straw

  • cotton and wool rags (must be 100% natural)

  • hair

GREENS - nitrogen rich
Greens are materials that go soggy and smell if there is too much of it in one place.

  • fresh grass clippings

  • garden weeds without seeds

  • Fruit and vegetable scraps

  • seaweed

  • tea leaves and bags

  • coffee grounds

  • animal manure (grass eaters only)

Don't include:

  • meat or fish

  • dairy products

  • fats

  • oils

  • anything toxic (e.g. sprayed weeds)

  • anything artificial like plastic or acrylic

  • invasive weeds like couch grass and convolvulus (unless very dead)

  • weed seeds

  • dog and cat poo

  • Coal ashes

Opinions differ on the exact ratios to use, but in general a larger amount of Carbon to Nitrogen (the C:N ratio), say 1:1 (half carbon half nitrogen materials) will make a richer, faster composting heap, whereas a higher ratio, say 5:1 (5 parts carbon to 1 part nitrogen) will produce a more bulked up, slower composting heap good for applying as a mulch.

When finished it will be 30% of its original volume and will resemble dark crumbly soil. To get the maximum benefit from compost as a source of plant nutrients it should be applied to the soil surface in the spring. Do not dig-in your compost. Apply it as a surface mulch at the rate of 1 bucketful per square metre. Spread it on top of the soil and lightly fork it into the top couple of centimetres.

Healthy soil = Healthy Food = Healthy People



Starting a worm farm is easy - and it is a great way to turn vegetable scraps, coffee grounds etc into fertiliser for your garden. 

One thing I really like about worm farming is that you can keep it quite well contained, meaning that rats do not get in to eat the food like they can in a compost heap. Personally, I run all of my vegetable based food scraps through a worm farm, and I put my more bulk materials (such as garden trimmings and other non-food items that don't attract rats) into a compost heap. 


The process is fairly simple. Tiger worms (also known as red wrigglers, the type of worms used in worm farming) eat fresh organic matter. In nature, they live in the top soil level, eating freshly fallen leaves and fruits and helping in the process of turning them into soil.

Worm farming is simply about replicating this natural process. Basically you set up a worm farm, source some worms, and begin feeding them your vege scraps etc. The worms naturally move into the areas of fresher material when they're done eating the first stuff. Through time, the worms will turn this food into a rich form of compost called worm castings, which is a great soil amendment. Additionally, worm farms produce a rich liquid which can be diluted and used as a liquid fertiliser. 


There are two main types of worm farm you will see in kiwi gardens. 


This system is perfect for those with limited space, or if you want to keep your worm farm nicely contained. The basic idea is that you have two to three bins which can stack on top of each other.


You start with the first bin, and when that is full of scraps, place the second bin on top of that, directly on top of the scraps. The worms naturally begin to crawl up through the drainage holes and into the fresh material. When the second bin is full, you can add a third. 

By the time the third (top) bin is full, the bottom bin should be finished composting. You can empty the worm castings onto the garden, and then continue the process, placing the newly emptied bin on top.

Stacked bin systems usually also have a collection tray underneath, to collect the worm juice ('worm tea') that leaks out. This can be used diluted down 10 to 1 as a liquid fertiliser. See this illustration for an example of a cheap and easy to make three bin system. If you have further questions about worm farming, join up to the Worm Farming NZ facebook group for plenty of helpful advice. 


Another system you'll see frequently used around the place is bathtub worm farms. People also improvise similar systems out of other types of containers, but the core idea is the same. This larger tub system is suitable for people with larger properties, or larger volumes of organic waste to get through. 

Basically a bathtub worm farm works similarly to a stacked bin system. However instead of rotating bins, you simply slowly move around the area where you are placing your fresh worm food. For example, starting at one end of the bathtub, making a stack of food, and then slowly making your way up to the other end of the bath tub. By the time you reach the other end, the first scraps that were put in should be fully processed and ready for use on the garden and then start adding fresh scraps from that end again. 

Usually people will place the bathtub on a stand (such as cinder blocks or blocks of wood - just make sure it is sturdy) and leave the drain hole of the bathtub open with a container placed underneath to collect the worm tea. 

For this type of system, a cover is needed over top of the scraps to keep the farm damp and dark. People often use old carpet, but if you are to do so, I would recommend making sure that it is a pure wool and other natural materials carpet, not synthetic fibres. Old coffee sacks can also be used for this purpose. Some people make a plywood lid that fits over the whole bath. 


Most garden centres have containers of live tiger worms for sale. However, they are quite pricey, and tiger worms are usually pretty easy to find yourself! If you or a friend or neighbour has a well established compost bin, or an old pile of grass clippings in the corner of the yard, chances are tiger worms will have already taken up residency. Or, if you know anyone with a worm farm already, they'll probably spare you a few worms to get started.


Simply grab a few handfuls of them and transfer them into your new worm farm. Make sure they are tiger worms and not earthworms. Tiger worms have distinctive darker red rings all down their body. Whereas earth worms are a lighter pink colour with no obvious rings. Earth worms live in soil whereas tiger worms live in decaying organic matter. 


There are a few basic rules that you need to follow to keep your worms happy and healthy. Most importantly, they need: 

  • The right kinds of food 
    Tiger worms love fresh organic matter. The kinds of things I tend to feed them is mostly vege scraps, coffee grounds, tea bags, grass clippings, and weeds. Shredded paper, egg cartons or straw are also fine, and can help balance things out if it gets too gluggy (same as a compost heap). Worms eat using a gizzard which requires some grit to function well, so the odd sprinkling of sand does not go astray either. Pretty much any plant matter is fine - things to AVOID include excessive amounts of citrus, onions, fats and oils, salted or spiced foods

  • Moisture
    Worms like moisture, but not too much or they'll drown. If you notice your worm farm seems a bit dry, don't hesitate to give them a sprinkle with a watering can or gently pour a litre or two of water into the worm farm now and then. 

  • Balanced pH
    Just like a compost heap, the process of decay in a worm farm can sometimes turn slightly acidic. A light dusting of garden lime on top of freshly added scraps now and then helps keep the pH in check and gives the worms some calcium. 

  • Avoid extreme temperatures (below zeroish or above 30ish)
    Worms are generally pretty resilient, but they don't enjoy getting absolutely cooked or frozen solid. If you live in a particularly cold climate, some degree of insulation might be required in the winter during hard frosts. In Coastal Otago, my worms do fine without insulation, however I have them next to the house under the eaves so they are protected from hard frost. 
    In summer, avoid having your worm farm exposed to direct sunlight or in a really hot area for too many hours a day. 
    Under a tree is a great place for a worm farm. Shaded in summer, and protected from direct frost in winter! 

Good luck and happy worm farming! 

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