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CompostingCompost compositionAeration Moisture Nutrient preservation Disease prevention When is the compost ready? Composting is easyComposting is one of the most important elements of the organic method. Plant residues that are not eaten should be composted along with hay, manure, lawn trimmings and whatever nontoxic organic material you can scramble. All organic materials put on the ground will decompose eventually. The breaking down results from the activities of two different sets of microorganisms. One set is active if air and oxygen is present. The other if there is no air. In the latter case decomposition will be slower. The smell of an anaerobic heap will often be vile due to the formation of foul smelling substances, and the compost (or sludge) that result will be less useful - at least in the short term. When air is present the pace is much quicker. If kitchen waste is added the smell may still be unpleasant, but if you stick to garden waste and manure this will rarely be the case. Composting is not difficult. It is actually hard to stop the process. But if it is done well the process is faster and the resulting compost richer.
The composting process is quicker if a large amount of material is added at once, but it is also possible to build a heap by successive additions. A simple open heap on the ground will work, but I prefer a wooden construction with two compartments, one cubic meter each.
There are five factors to consider producing the best quality compost.
Compost compositionPlant residues consist of primarily (95 percent of the dry weight) oxygen, carbon and hydrogen combined in large organic molecules. Plants use the sun's energy to produce these molecules. By breaking down these organic molecules different organisms can release this energy, as do you and I.
Top AerationWhen the microbial activity in the heap is high the heap will be quite warm. Warm air rises. If you make sure that air can come in under the heap aeration will probably be fairly good. One way is to put some plastic drainpipes in the bottom when the heap is built. Some organic materials tend to form compact layers that do not permit air to circulate freely in the heap. Leaf and lawn trimmings are the worst. These are very good materials for the compost, but be sure to mix them thoroughly with other materials. Some twigs and other coarser materials improves the circulation of air, and are not difficult to remove when the compost is ready. It's also a good idea to turn the compost after a couple of weeks with a garden fork to create new air channels.Top MoistureThe microorganisms live in the thin film of water that covers all moist organic matter. All the chemical processes that lead to decomposition take place in water. Without water there will be no activity at all. The organisms do not drown in water. It's when to much water prevents the circulation of air that they will die. When this happens the anoxic set of microorganisms take over in the oxygen free environment. This is often restricted to pockets within the heap, but is still enough to cause problems. The material should be quite moist, but water should not be dripping from it. Ants and white fungi mycelium are signs that the heap is to dry. If it is primarily fresh and green plant matter that is composted the heap will often be to wet. If this happens the material can be spread on the ground to dry up a little. You can also mix in some hay, drier matter or old compost. Don't use peat. The use of peat leads to severe and unnecessary destruction of the natural habitats where it originates.Top Nutrient preservationDuring the summer the problem is usually that the compost gets to dry. It has to be watered for the process to continue. For the rest of the year compost exposed to rain will be to wet. Water flows through the compost and into the ground taking dissolved nutrients with it. To conserve nutrients the heap should be covered before it gets to wet. Make sure that air can circulate under the cover, especially if the heap is still highly active.Top Disease preventionIt's true that composting will kill many pests and diseases. Heat and competition will both make it difficult for unwanted organisms to survive. However, efficiency is far from 100 percent. It's therefore wise not to put material that is obviously infested or diseased in the compost. Burn it or remove it far from the garden.Top When is the compost ready?When the compost is ready is a difficult question. If the oxygen has temporarily been depleted during the process, the compost may contain substances that are toxic to plants or interfere with seed germination. In this case we may have to wait for several months for these substances to disappear, which they will do with time. I have used compost that was only a couple of months with success. If you want to be sure you should leave the compost to mature for a year.Top
vegetables@frideen.com Last major update 2004-12-10 Copyright© Anders Frideen |
The size can be varied to suit your needs, but the container should never be taller than one meter to ensure good aeration. I make the sides without gaps. If there are gaps between the boards the exterior parts of the compost will dry which is bad because moisture is necessary for the process to proceed. If a compost heap has a well-balanced composition and is large enough to provide good insulation the temperature will rise sharply during the first week. It's a dramatic increase in the number of microorganisms and their activity that produces this effect. The temperature can be as high as 70oC. This is enough to burn your fingers if you put them in (a hot bath is around 40 degrees). It doesn't get any hotter than this because the most heat lowing of the microorganisms are inactivated at this temperature. After the sharp rise, the temperature will fall again. After a month or two it will be close to that of the surroundings. If the material is turned after two to three weeks the temperature will rise again. The highest temperatures do not increase the speed of decomposition. Decomposition is fastest at temperatures around 45oC, but higher temperatures can kill some weed seeds, pests and disease causing organisms.
