Composting - the helpful home guide

Compost is... Plant and animal material naturally broken down by worms and soil bacteria and fungi. It is a natural plant food, soil conditioner and mulch. Why compost? It will enhance your garden. Compost: encourages plant growth improves drainage in heavy clay soil and conserves water in light sandy soil keeps the soil cooler in summer, warmer in winter increases aeration in compacted soil

It saves you money because it: halves rubbish removal costs reduces the need to water the garden reduces the need for artificial fertilisers All you need to do is gather together waste organic materials and mix them in a compost bin or heap. Worms and other critters will do the rest. It saves the environment Reducing rubbish and your reliance on water and artificial fertilisers is a simple way to help the environment. When everything ends up in the landfill we are throwing away precious resources and creating potential problems. Some of these problems are expensive, such as long term monitoring of filled landfills.

Create Your Own Eden

Tasman District and Nelson City Councils have joined the national Create Your Own Eden programme.  This programme provides resources and a website to provide you with all the information you need to know on how to make great compost, improve your soil and produce fantastic fertilisers for your plants, veggies and garden all for free. The site covers traditional composting using a heap or bin, vermiculture or worm farming, and Bokashi.  The Create Your Own Eden website and associated resources is available from here.

Compost Vouchers

Tasman District and Nelson City Councils encourage home composting. They offer a $15 subsidy on the purchase of compost bins and worm farms. Just call into any Council office for a compost bin coupon, before buying your bin from any of the listed retailers.
 

What to compost

Materials you can compost are:

• vegetable and fruit scraps, tea leaves and coffee grounds
• vacuum cleaner dust and untreated wood ash
• old potting mix, leaves, garden and lawn clippings, weeds (if they have not gone to seed)
• sawdust, straw, animal manures, and seaweed.

Materials not to compost are:

• meat, fish, fats or cooking/salad oils (these may create odour and fly problems)
• wood, bones, diseased plant material
• plant foliage with residues of chemical sprays, especially hormone type weedkillers
• oxalis, and other probLem weeds such as live twitch, convolvulus, docks and dandelion.

Siting your bin

You can either buy a bin or make an enclosure yourself. Locate your compost bin in a sheltered area, preferably not in full sun. The compost heap should sit directly on the soil.
 

Download Resources

Garbage Muncher - information on how to build your own compost bin

Hints for use of Plastic Compost Bins - further advice if you have a plastic compost bin
 

Setting up the bin

1. Before positioning the bin, fork over the soil on the site to aid drainage and encourage earthworms into the heap.
2. Start the heap by placing a 10 - 15cm layer of coarse twiggy materials (coarse partly decomposed materials from a previous heap may be used) at the bottom of the bin to ensure good drainage and entry of air.
3. Add:
   • kitchen and garden wastes
   • manure, soil, blood and bone or a compost activator.
4. If the compost heap is regularly turned it will be ready in 3 - 4 months. If the compost is not turned allow 9 -12 months for the heap to mature.

Tips

• Chopping or shredding coarse materials into small pieces before composting speeds up the process.
• Coarse and fine material should be well mixed together.
• Dampen your heap regularly in summer to maintain the consistency of a squeezed out sponge.
• Decomposition is faster in the warm summer months because the rate is dependent on temperature.
• Compost is mature when it has darkened and is a crumbly soil like material. If used too soon it may borrow nitrogen from the soil as it breaks down. This will limit the nitrogen available to growing plants.
• The heap needs to be large enough to maintain heat for microbiological activity. A cubic metre or slightly larger is sufficient size.

Download Resources

If you have any problems with your compost please refer here for some advice.
To improve the mineral content of your compost refer here for some advice.
A poster that explains how to compost.
 

Using compost

Mix into the soil or use it as a mulch on the soil surface. Either way it will result in improved soil stability, increased soil fertility and a boom in the earthworm population.

• Real benefits occur if compost amounts to more than 25 percent of topsoil volume. Compost breaks down in the soil and needs to be replenished regularly. There can never be too much compost.
• Partly decayed or unfinished compost makes the best mulch for suppressing weeds, but it needs to be at least 10cm deep to be effective. Do not use partly decayed compost in the subsoil or at depths greater than 15cm or hydrogen sulphide gas - which is toxic to plant roots - may be released.
• To avoid fungal decay, do not pile compost up against tree trunks or plant stems.
• If you have added lime to your compost do not use it around azaleas, camellias, rhododendrons, pieris, ericas and acid loving natives.
• When planting trees and shrubs do not put compost into the bottom of the hole.
• To avoid disturbing the roots of established trees and shrubs it is best to use compost as a surface mulch rather than dig it in. In time earthworms will drag it down and mix it with the soil without harming plant roots.