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It's been understood since ancient times that what comes from the earth should be returned to the earth. And the best way of returning the earth's richest (with interest) is to build a compost heap. Composting everyday plant debris and kitchen scraps results in rich humus, the decomposed organic matter, that's essential for good garden soil. Humus helps soil hold water, allows for air flow, controls erosion, and creates a home for the bacteria that protect plants against disease, capture airborne nitrogen, lure soil-enriching earthworms, and ferry minerals from the subsoil.

Composting is an ideal way to dispose of organic household refuse such as lawn clippings, leaves, and many kitchen scraps. After six months to a year of composting, you'll be rewarded with pungent, coffee-dark, crumbly humus that helps plants thrive.

The best compost combines 2 to 3 parts "brown," or carbon-rich materials, with 1 part "green," or nitrogen-rich materials. Never add materials treated with poisons or pesticides that will contaminate the compost. Most gardeners keep two piles, one started about 6 months after the first. This way, they can use the compost from the first pile as the other is decomposing.

Materials
Compost bin, commercial or homemade, with at least a 1-cubic-yard capacity
Brown (carbon-rich) materials, such as dried leaves and pine needles, sawdust, shredded newspaper, straw, small twigs, and wood chips
Green (nitrogen-rich) materials, such as grass clippings (free of pesticides), kitchen scraps and vegetable trimmings, and soft prunings or cuttings. Also good: coffee grounds and filters, eggshells, and deadheaded flowers
Garden fork
Compost thermometer (optional)
Compost bioactivator (optional)

Technique
1. Situate the compost pile in a partly shady area near a water source such as a garden hose. Choose a spot away from the garden and a few feet away from buildings.

2. Begin the compost with a 6- to 12-inch layer of brown material such as twigs or small branches to help air circulation. Build the pile over time by alternating 6- to 12-inch layers of green and brown material. Bury kitchen scraps beneath a layer of brown material to avoid attracting pests and producing odors. Add compost bioactivator, following label directions, and continue layering until bin is full or pile is 3 feet high.

3. Once layered, dampen the pile with water. Turning the pile with a garden fork, mixing the green and brown materials, will speed decomposition by improving air circulation and will reduce odors, but turning isn't essential.

4. Try to add equal amounts of green and brown materials to the pile periodically. And maintain a moisture level similar to that of a wrung-out sponge. Average rainfall will usually suffice -- if the compost becomes too dry, add water; if it becomes too wet, add dry materials like leaves or shredded newspaper.

5. Periodically measure compost's temperature: Healthy decomposition causes compost to literally heat up to between 130 degrees and 150 degrees. Once it begins cooling, turn the pile.

6. If you've turned the pile regularly, whenever new material is added, in about 3 months, the compost will resemble rich, crumbly potting soil, ready to use. Unturned piles take 6 months to a year.

First Published: September 1996