As Barbara Pleasant, author of "The Complete Compost Gardening Guide," put it, "Dead plants already know how to rot." The tendency to over-think composting leads to lost money, lost time and extra headaches when, in reality, compost is a natural process that has been happening without human help for millions of years. Effective composting involves replicating the conditions that best harness the power of nature.
What Goes In
At its most basic, compost is made from a mixture of ingredients that include nitrogen and ingredients that include carbon. Nitrogen-rich ingredients are called "greens" and tend to be moist. Grass clippings, egg shells and kitchen scraps all count as greens. Carbon-rich ingredients are called "browns" and include dry ingredients like dead leaves and paper shreds.
"Rodale's Ultimate Encyclopedia of Organic Gardening" recommends including two parts brown for every part green. Pleasant agrees that this is the optimal ratio but adds that most home gardeners don't have to worry that much about proportion. Precise proportions are meant to control pollutants in industrial composting operations. For the small-scale gardener, this isn't an issue.
Compost is produced by bacteria that live in the soil. These bacteria feed on carbon and use nitrogen to aid in reproduction, producing fertile soil as they munch away on old peels and lawn clippings. When starting a compost pile, add a handful of finished compost or rich soil to ensure that the bacteria you need are present.
Water and Air
Bacteria are living organisms and also require water and air to survive. In order for them to get to work making compost, you need to ensure that they have an adequate supply of both. When you add your first handful of helpful bacteria, wet down the pile to help them get started. Pleasant points out that compost heaps generally shrink with time and aerate themselves, so she doesn't insist that compost must be turned regularly in order to work. She does, however, say that turning your compost ensures that there aren't any dry spots in need of better mixing. Some compost units, called tumblers, allow you to turn your compost with a crank. If you are using a bin or an uncovered pile, occasionally mixing ingredients with a garden fork does the trick.
Producing usable compost fast--in less than eight weeks--requires a method called hot composting, so called because the compost reaches temperatures up to 160 degrees Fahrenheit. During hot composting, optimal conditions and frequent aeration via turning keep the helpful bacteria working at their peak, making more compost in less time. According to "Rodale's Ultimate Encyclopedia of Organic Gardening," hot composting can produce six or more batches of compost per year, even in cooler climates. If your garden soil is in need of a nutritional boost, hot composting may be a good option for you.
Hot composting has disadvantages. The hot temperatures could kill helpful microorganisms that prevent plant diseases. Also, because the bacteria are reproducing so quickly, hot compost is less nitrogen-rich and, therefore, less nutritive for soils that need a nitrogen addition.
Some materials are best avoided in your compost pile. Fats, bones and meat scraps will eventually compost, but they decompose slowly and, in the meantime, attract rodents and scavengers. Watch out also for herbicide-contaminated ingredients. As tempting as it might be to use grass clippings and leaves from your neighbor's yard, unless you're positive that they haven't been sprayed with weed killers or other herbicides, don't use them. Be cautious also of animal manures from unknown sources. Herbicides found in the animal's feed can persist in compost for years, stopping or stunting the growth of your plants.