Perhaps the most practical method of enriching soil is by amending it with compost. Production of compost is more work than acquisition of the other amendments discussed last week. However, it is an efficient use of garden and kitchen waste.

Compost piles about four to six feet tall retain much of the heat generated by decay, which accelerates continued decay. Decomposition is slower in small piles in which much of the heat dissipates. Very large piles may rot rather than decay in areas with inadequate air circulation. Bins may be used to contain compost and to direct heat upward more efficiently and evenly. It is important that organic matter is collected into a pile or bin rather than mixed directly into the soil. Otherwise, nitrogen which is necessary for decay will not be available to plants.

When a compost pile is initially constructed, it should contain various types of organic matter which are each added in layers on top of previous layers. Too much of one type of material will likely pack together, forming denser clumps which decay slower and smell bad. Grass clippings seem to form clumps unless  spread in very thin layers. Thicker layers of grass are possible if the grass is first spread out to dry on another larger surface, or mixed with coarser material. Although most material is collected from around the home, some prefer to also add horse or steer manure if it is available. A small quantity of top soil added to the upper layers may also be helpful.

Coarse material should be chopped or ground to maximize surface area for decay organisms to work on. Most foliar litter decays quickly; but larger stems may not. Compost grinders are useful for those who produce large quantities of compost. Some prefer to bury larger branches within the compost pile. The leaves decay and the stems may be removed as the compost is turned or used. (It is like making chicken soup and removing the bones when it is done.) Coarse material which is not chopped or ground will eventually decay; it will simply require more time. Of course, some material decays slower than others. For example, leaves of southern magnolia have a thick, waxy cuticle and consequently decay much slower than the delicate leaves of silver maples.

Compost piles should be kept moist, but not wet. Too much water in the pile inhibits air circulation. During the rainy season, it is helpful to cover compost at least part of the time. If it becomes too wet, it may be “fluffed” with a pitch fork during better weather.

Although most organic garden and kitchen waste is suitable for a compost pile, certain “ingredients” should be avoided. Meat scraps, bone or fat from the kitchen may literally smell like something died in the garden, and attract cats, dogs, rats, possums and who knows what else! Seeds or pits, such as those found in cherries, apricots, peaches and avocados should also be discarded so that they do not grow into trees in strange places in the garden. Similarly, garden waste which contains weed seeds or spores from fungal diseases (such as rust or powdery mildew) should also be discarded.

Although manure must be aged prior to incorporation into garden soil, it is best added to compost fresh, so that the bacteria responsible for decay may enjoy the extra nitrogen. If manure is not available, extra nitrogen may be added as blood meal or high nitrogen, slow-release fertilizer.

It may take some time to collect enough organic matter to assemble a complete compost pile; but once it is established, it should be “turned” every few weeks. Turning involves separating the top material into a new pile onto which the lower material is layered. This process places the less decomposed material in the center of the pile where decay is more active, as well as aerates the compost. After about three months, the compost should be rather loose and sufficiently decomposed, so that individual plant parts can not be identified. At this stage, it is suitable for incorporation into garden soil.