Revision as of 21:30, 31 January 2006

This is the stub of an article on compost. I'm sure there's a lot more can be said - Ceratonia.

Why Compost?

Incorporating compost into your soil improves the soil structure - addition of organic matter improves drainage, water holding capacity and aeration. It also provides valuable nutrients. In short, it makes your plants grow better!

Making your own compost saves money and reduces the amount of waste going to landfill sites. And digging rich, brown, crumbly friable compost out of a heap is a very satisfying part of growing stuff.

How do I make compost?

In essence, you make a big heap of compostable material and wait. The actual decomposition is done by a wide variety of earthworms, fungi, bacteria and other small creatures. The time to produce useable compost could be as short as two months, or as long as two years.

You can shorten the waiting time and improve the quality of the final product by paying attention to the balance of materials in the heap, by ensuring the correct amounts of water and air reach the decomposing material, by raising the temperature of the heap and by regular mixing.

Water is required for composting - very dry matter will take a long time to rot. On the other hand, too much water will stop the heap getting hot and wash away nutrients. Air is also required - this can be a problem if the heap becomes compressed, with no bulky material (eg all grass cuttings). Anaerobic decomposition is the result - the heap gets slimy and smelly.

Mixing simply means that the heap typically has to be turned once or twice. Having multiple compost bins may make this easier.

Shredding the material before it goes on the heap makes a big difference to decomposition times - it gives more surface area to the bacteria, better aeration and better mixing.

What can be composted?

Plant material - fallen leaves, weeds, prunings, grass cuttings, manure, straw and hay, newspaper, cardboard, vegetable and fruit scraps, tea bags etc. Avoid meat, fish, cooked food, dog and cat "manure", glossy paper, ash from coal fires. Some materials (eg tree branches/twigs & other woody plants) may take a long time to decompose and may not be worth composting.

You should also avoid composting diseased plant material. The hot temperature of the heap will kill certain problems, but others (eg clubroot, white rot) may survive. Similarly, it is often sensible to avoid composting weeds with seedheads or perennial weeds such as bindweed or ground elder. Again, a hot heap will sterilise these problems, but a colder heap may not. Eucalyptus leaves should not be composted, as they can be toxic to other plants. Holly leaves take for ever to decompose.

Better results are obtained by ensuring a balamnce between 'brown' (eg fallen leaves) and 'green' material (eg grass cuttings). This relates to the ratio of carbon to nitrogen in the heap.

Compost bins

These can be the green daleks that many councils give away or sell cheaply. Or a wooden bin, made of old pallets. In general, the bigger the heap, the hotter it will get and the better the decomposition process.

How to use compost

Use it as a mulch, or dig it in!

Compost Tea

It's liquid compost. Take your compost, add water, strain and use as a liquid feed

Composting with worms

This is a special method, used to produce wormcasts from food scraps. Very different from normal outdoor composting.