You can never have too much compost. Unless you work on a farm or you collect all your neighbours’ kitchen and garden waste, it’s unlikely you will be able to produce anywhere near what you need to grow your crops. So do compost everything you possibly can, but be prepared to supplement it too.
Compost is any plant matter that has decomposed. It is highly rich in nutrients and we use it in organic gardening as a fertile material in which to grow our food. The key to good compost is a balanced ratio of carbonic and nitrogenous material, also known as brown and green material. Carbon-rich brown material includes dead leaves, twigs and cardboard, while nitrogen-rich green materials include, as you would expect, any green parts of the plant, as well fruit and vegetable peelings. Ideally you want your compost to be made up of brown and green materials in roughly equal measure. You can also add coffee grinds and egg shells to your compost, to improve its structure. You can compost any kitchen and garden waste, with the exception of meat and dairy products. Some organisations advise against composting cooked vegetables as they may attract rats, but there is little evidence to support that rats prefer cooked to raw vegetables.
If you are lucky enough to have a large outdoor growing space, you may want to consider building a two or three-stage composter out of wooden pallets. This allows you to turn (aerate) your compost, and move it along as it decomposes. The idea is that new waste goes in one bin, and as it decomposes you move it to the next bin to make room for new waste:
Realistically, most of us haven’t got room for this, and so a large bin on a balcony or outside has to suffice. Make sure you turn, or stir the compost every so often to aerate it and prevent anaerobic respiration. Urine is the best catalyst for decomposition and I regularly send my partner out to the compost bin to help it along. Once the compost has become humus, or that rich dark brown state which isn’t going to decompose any more, you can apply it to your crops, or sow your seeds straight into it.
You can supplement your compost supply by contacting your local council’s environment department, who either sell or give away the compost they collect in those blue and brown bins from people’s houses. In London, the East London Community Recycling Partnership also provides compost, as does Freightliners City Farm, who will sell you 80 litres of their organic compost for £5. Bargain.
If you need to buy compost from the garden centre, choose peat-free compost, which doesn’t contribute to the depletion of peat bogs and impact the wildlife they sustain. More about that here.