Composting is simply the natural decomposition of organic matter. It is a process that is occurring constantly all around us. Compost is produced through the activity of tiny organisms known as decomposers. Given a favorable environment, they will break down your yard wastes and kitchen scraps into a humus-like material that can serve as an excellent soil amendment for your yard and garden.

Once you have established your compost pile, the decomposters go to work almost immediately. At one time or another, your pile will probably be populated by fungi, bacteria, protozoa, roundworms, flatworms, snails and slugs, various types of insect larvae, millipedes, bettles, mites, centipedes and more. Different organisms prefer different organic materials and temperatures; as the conditions in the pile change, the mix of organisms will change, too, with some organisms becoming dormant, dying, or moving to another, more hospitable, part of the pile.

Probably the most important thing to know about the organisms involved in composting is that the most desirable decomposers require oxygen. If your pile becomes oxygen deficient, these desirable organisms will die, and anaerobic decomposers (those not requiring oxygen) will take over. The anaerobic decomposers will generate odorous products as well as acids and alcohols that can harm plants. You can make sure that your compost remains oxygen rich simply by turning or mixing the pile every week or so, or anytime you notice it becoming odorous.

First, choose a location for your compost bin. Here are a few suggestions: Choose a spot that is flat and well drained. A shady location is preferable; direct sunlight may cause the pile to become too hot and to dry out. Place the bin at least 20 feet away from the nearest house. Make sure the bin is close to a source of water (e.g., within reach of a garden hose). Avoid placing the bin against a tree or wooden building; the compost could cause the wood to decay.

Once your bin is in place, you can begin immediately to fill it with yard wastes and kitchen scraps (see Table 1 for a list of what can and can not be put into the composter). If you have been stockpiling materials such as leaves or garden wastes, you can put them into the composter all at once, or you can put a small quantity (a 4- to 6- inch layer) of the stockpiled material in the composter and add the rest gradually, alternating it with layers of other materials as they become available. Alternating the types of materials you add to the bin will speed up the decomposition process, especially if you alternate high-carbon materials with high-nitrogen materials and mix the contents of the composter occasionally. See Table 2 for a listing of high-carbon (“brown”) and high-nitrogen (“green”) material.

It may be helpful, when first building your compost pile, to mix in a small amount (no more than ½ shovelful) of rich garden soil or finished compost; both are good sources of microorganisms essential to decomposition.

You can choose how much effort to put into maintaining your compost pile. If you are not able or inclined to shred and chop your wastes and to water and turn your pile, your organic matter will still turn into compost – it will simply take longer. Here are some tips for speeding up the process.

• Chop or shred materials before adding them to the composter. Small particles decompose more quickly than large ones. Run over your leaves a couple of times with the lawn mower before adding them to the bin; cut yard trimmings into short pieces; chop up celery stalks.
• Keep the pile moist – about like a well wrung sponge.
• Mix or turn the pile occasionally, especially during warm weather or if you notice that the pile is hot. Mixing will aerate the pile, providing oxygen needed by the more desirable decomposing organisms, and thereby controlling odors. Once every week or two will probably suffice.
• Add nitrogen. Most backyard composters have an over-abundance of carbon, so that the process is limited by the nitrogen available in the pile. Livestock manure (from cows, horses, pigs, chickens, etc.) is rich in nitrogen and can safely be added to your compost pile. Do not add manure from cats, dogs, or other meat eaters.

Finished compost will tend to accumulate at the bottom of your bin. It is ready for use when it is dark brown and crumbly, with an earthy aroma. If you have observed the techniques listed above, you may have usable compost in 2 to 3 months; otherwise, your material may require as much as a year or two to completely decompose.

Compost can be used in a variety of ways to benefit your lawn and garden. Here are some suggestions.

In the garden

• Spread a 3- or 4-inch layer of compost on top of the garden, and work it into the soil before planting(in spring or late fall).
• Apply the compost as a top dressing to shrubs and garden plants; either leave the compost on the surface or work it into the soil (this can be done several times a year).
• Incorporate compost into feed furrows. Place a handful into each transplant hole before transplanting annuals and perennnials; use several handfuls for shrubs and trees.

On the lawn

• When building a new lawn, spread a 2-inch layer of compost over the area and work it into the soil to a depth of 6 inches.
• On an existing lawn, use compost as a top dressing by applying it in a uniform layer about 1/4 inch thick. You can use a fertilizer spreader or broadcast the compost by hand, followed by light raking. The best time to top dress is in the fall. (Note: Only compost that has been sifted through a fine screen should be used in this manner. A simple screen can be made using a wooden frame and 3/8- or 1/2-inch hardware cloth.)

In potting mix

• You can make your own potting mix by combining fine-textured compost with sand, bark, and vermiculite or perlite.