A 3-feet-square compost pile is large enough to hold heat, but small enough to admit air. If a large pile is needed, build one that is 5 feet tall by 5 feet wide by any length.
Because microorganisms can only use molecules dissolved in water, moisture content should be 40 percent to 60 percent. The material should feel damp to the touch, with just a drop or two of water if squeezed.
To begin a compost pile, start with a 4- to 6-inch layer of chopped brush or coarse material. This allows air circulation under the pile. Next, add a 3- to 4-inch layer of damp organic material, such as low-carbon grass clippings. The next layer should be 4 to 6 inches of high-carbon organic material, such as dampened leaves or garden waste. Add an inch of garden soil or finished compost, which introduces microorganisms to break down organic matter. Mix the layers before adding more to the pile, to ensure speedy and even composting. Repeat the layering process until the bin is full.
A passive compost pile requires no additional maintenance. However, an active pile means the pile must be turned and water must be added to maintain conditions conducive to composting.
For an active compost pile, loosen materials and overturn them weekly. Sides should be moved to center, and the bottom layers should be moved to the top. Check the moisture content, and add water if necessary.
When the pile cools in temperature, decreasing in size to about one-third of the original volume and becoming dark and crumbly with an earthy odor, it’s ready to use. Don’t add partially decomposed materials; this can reduce the nitrogen available to plants.
Stable compost, which is suitable for most outdoor plantings, can be mixed with peat moss, shredded bark, sand or loamy topsoil. Ten percent compost is minimum, 30 percent is optimum, and 50 percent is maximum for planting shrubs and trees.
Rototilling compost directly into the soil is the most effective treatment. Spread compost no more than one-third the depth of the rototiller. Rototilling several times blends the compost with topsoil and breaks up clumps.
Equipment needed for composting includes a stiff-tined fork, a compost thermometer and a garden hose.
Building a compost pile has many advantages. Besides providing a means to recycle garden leaves and trash, this process amends the soil, which improves its structure and water-holding capacities. It also releases plant nutrients, including nitrogen, and it fertilizes the soil. It is the answer to many gardening dilemmas.