All About Compost
What is Compost?
Compost is decomposed organic material; almost exclusively vegetable matter. Good compost is suitable for use in your garden soils to return nutrients to the soil and improve soil condition by providing humus, moisture retention and beneficial micro-organisms.
Well decomposed compost will be brown, sweet-smelling and friable (breaks up easily). Don’t use it if it is green, slimy*, foul-smelling or does not break up easily.
*In wet conditions, the compost may become waterlogged and slimy. See below regarding the best conditions for your compost heap.
Where to Compost
You can compost by creating a pile in a corner of the garden. This is simple; all you need is the space somewhere where water will drain well - Do not use a place where puddles form. The minimum size will be 1 m3 (1 m x 1 m x 1 m). A simple pile leaves much of the exterior of the pile (top and sides) exposed to the elements. In dry weather, the exterior will dry out and the micro-organisms that breakdown the organic matter will not thrive. In cold weather, the exterior will not have enough heat to keep the micro-organisms actively breaking down the organic matter. Exposed piles need to be turned and mixed regularly. It is best to have two such piles so that you can be adding ‘stuff’ to one while the other is finishing composting completely - if you only have one compost heap the most recent additions to the heap will not have composted fully while other parts are ready.
The more you can enclose a pile, more of the whole pile will have good conditions for the micro-organisms and you will get even decomposition. There are many simple designs for compost bins and there are ready to use bins in hardware stores. Most cover at least three sides of the pile; three sides will reduce the exposure to elements by more than 50%. You can also cover the top, but be sure that some moisture and air is able to circulate into and around the top of the heap. Choose a bin design and size that suits your garden and the amount of vegetable matter you will compost from your kitchen and your garden.
The temperature of the compost pile is an indication of the micro-organism activity of the decomposition. The easy way to check the temperature inside the heap is by feeling it with your hand. If it is warm or hot, decomposition is as it should be, but if it is the same temperature as the surrounding air activity has slowed down and you need to add more materials that are high in nitrogen to the bin; green stuff. E.g. leaves, grass clippings.
See the article about Keeping Your Compost Cosy In Winter.
Dos and Don’ts of Composting
- Do find a suitable place to site your compost pile/s.
Don’t site your compost in a place that puddles form regularly.
- Do give your compost protection from the worst of the elements.
Don’t restrict access to the compost for turning.
- Do cover the compost with something that insulates the pile.
Don’t cover your compost with polythene or other covers that would stop air and moisture.
- Do use non-diseased plant matter from the garden.
Don’t use diseased plant matter from the garden.
- Do use weeds from the garden before they have produced seeds, but avoid roots of weeds that may re-sprout from root fragments.
Don’t use weeds that have seeded.
- Do shred heavy materials such as branches and twigs.
Don’t use large pieces of woody material in the heap; these take too long to break down (compost them separately).
- Do turn your pile regularly (every 1-2 weeks) to get oxygen into the pile.
Don’t leave your pile more than a month without turning; compaction will reduce air and cause slow anaerobic decomposition and bad smells.
- Do move material from the outside to the inside and from the top to the bottom.
Don’t just turn the surface layers.
- Do compost lawn clippings in several thin layers with other materials between the layers.
Don’t add a thick layer of lawn clippings or autumn leaves.
- Do check the moisture of your compost pile; if it's dry add green stuff (e.g. leaves) if its wet and slimy add dry brown stuff (e.g. wood shavings, hay).
Don’t let your pile get very wet or very dry; it should be moist and steamy in the middle.
- Do keep your pile insulated in cold weather.
Don’t let the compost get cold.
- Do worry about rats burrowing in the compost pile.
Don't worry about earthworms and insects in the pile.
- Kitchen vegetable scraps (add only small amounts of citrus fruit)
- Autumn leaves
- Lawn clippings
- Weeds (without seeds)
- The dung of herbivores (horses, rabbits, etc.)
- Wood ash (limit to a sprinkling) See Using Wood Ash in Your Compost
- Wood shavings
- Shredded cardboard
- Tea leaves/bags
- Coffee grounds
- Cooked food
- Oils and fats (a little vegetable oil is OK)
- The dung of meat-eating animals (dogs, cats, etc.)
- Coal/charcoal ash
- Inorganic materials (plastics, metals, etc.)
Other Composting Tips
- Small stuff breaks down faster, so chop stuff up if it is more than 10 cm.
- Check the moisture level of your compost; if it is dry add green stuff or wet it, if it is wet mix in dry brown stuff.
- Don’t use your compost in the garden until it has been composting for at least 6 months. Compost that has not fully decomposed can take nitrogen from the soil and reduce the nutrients available to plants.
- You can speed up slow composting by adding LawnPro D-Thatch as a compost booster.
- Sift the compost through a coarse mesh screen or use your hands or fork to remove any larger lumps.
- Compost can be dug into the top layer of soil or can be added to the surface as a mulch that will continue to breakdown and release nutrients into the soil below. See 'Top Dress or Dig In'.