Conditions necessary for good composting

Obviously, the first requirement is something to compost. Then the pile needs air, nitrogen, water, bacteria, and sometimes lime. There are a great many old wives’ tales about what can and cannot be used, but the rule is, in fact, very simple: anything that is entirely organic in origin can be composted, except for a few things that common sense tells you should be left out, such as some diseased material, cooked kitchen scraps, and so on. The list of organic material that can be used is endless—you should never waste anything that will rot. Do not just throw things onto the heap, but mix different materials together to make sure that air can circulate through the heap—even if that means storing some material beside the pile until you have something else to add to it. Grass cuttings, for example, if put on the heap in thick layers, will form an airless mass and turn into slime.

AIR CIRCULATION

Air is of vital importance in the compost heap. Without it the material is worked on by a different group of microorganisms, known as anaerobic bacteria. If allowed to develop, they turn grass cuttings and any other material into a stinking slime that is worse than useless on the garden. The container should have air circulating through it and a good variety of material will create plenty of natural air spaces, so never pack down the contents too much. This can also be improved by mixing the fine material such as grass cuttings and small weeds with larger weeds, shredded newspaper, or straw.

NITROGEN

Because the bacteria in the compost heap require nitrogen as a fuel, you must add a certain amount to the heap. Ideally, use animal manure as your source. I keep hens in a movable henhouse with a run that is moved around the vegetable plot whenever space becomes available. I use the droppings from the henhouse to provide the additional nitrogen for my compost heap. But I am lucky to be able to do this. If animal manure is unavailable, you can buy organic compost fuels, or activators, in most garden stores. Alternatively, dried sewage sludge can often be obtained from the local sewage company—this is ideal not only for the compost heap but also for use as a fertilizer. Kelp (seaweed) meal is excellent and dried blood, the best form of nitrogen fertilizer, makes a very good, if slightly expensive, compost activator.

Whatever you use, you don’t actually need very much—and not as much as the manufacturers would have you believe. A fine dusting every 12in (30cm) of compost is sufficient.

LIME

Adding lime will keep the compost “sweet”—that is, it will help neutralize the acidity. However, adding a good mixture of material will create a sweet heap without the need to add lime. If you have chalky soil, you may feel that it would be better to omit the lime and use very acid compost to adjust the balance, and you can do this. However, the bacteria involved in rotting the compost material actually prefer conditions that are not too acid so, if you do not add lime, the rotting process takes longer. All in all it is best to use it. You should apply a slightly heavier dusting of lime than of the nitrogen activator every 12in (30cm).

WATER

This is an essential ingredient of any compost heap. Generally, there will already be enough in the green material you put on the compost heap. This is certainly the case if you use grass cuttings. However, it is possible, in a hot summer, for the edges to dry out, and then you may need to apply extra water. The same may be true if you have used straw in the heap. Straw makes an excellent aerating material, especially when used with grass cuttings, and it composts well, but you need to wet it first. I have composted straw on its own, but I found that I needed to put the sprinkler on the heap for half an hour at a time to wet it sufficiently. You may need to cover the compost heap with plastic sheeting in the winter, not only to keep the heat in, but also to prevent the compost from getting too wet.

HEAT

Although perhaps not absolutely necessary, there is no doubt that decomposition is much faster when the material is warm. In the summer you’ll have usable compost in only two or three months where, in the winter, the process slows down considerably and the compost will not be usable until the spring. You can cover the heap with black plastic weighted at the edges; this will keep the heat in and prevent it becoming too wet, which can be a problem, particularly in winter. I prefer to place a piece of old carpet over the heap; it does not need weighting down and also “breathes,” allowing more air into the heap.

BACTERIA

Finally, you need the bacteria themselves. This is the easiest job of all. There are millions in just one piece of soil, so there should be plenty in the clumps of earth that cling to the roots of the weeds you put in the heap. Some people recommend that you add layers of soil throughout the heap. In fact, this is completely unnecessary: not only is it hard work, but it also makes the compost less concentrated.