There seems to be almost as many ways of making compost as there are gardeners. Jeanie Darlington gave us her recipe for a compost pile in MOTHER EARTH NEWS Issue No. 3 and briefly described a method of composting in the ground in No. Four. Still, we find that some folks (new to organic gardening) continue to worry about the seemingly magical transformation of garbage into rich, black soil. So here, one more time (A HEAP Of Help For The Gardener), is a more-or-less standard set of directions for making compost. Then—just in case you start worrying about what to put in and what to put out of your compost, how long to let the pile set before turning it, whether or not to add "activators", etc.—we'll direct your attention to the other two articles on composting in this issue Creating Compost Potting Soil from Garbage and How the Compost Pile Turned into a Thriving Rock Garden. Get the idea? Dump your garbage together and stand back. It's almost impossible to fail!
How to Compost
The compost pile or "heap"—a mixture of decayed vegetable matter sometimes combined with manure—is an invaluable, yet inexpensive, device for providing the gardener with top-grade soil. Through the work of harmless bacteria, raw organic matter is converted—or "composted"—into humus. This humus is excellent plant food and improves the soil in many ways. A compost pile is built of substances such as dead leaves, lawn cuttings, left-over vegetables from the kitchen, manure, fertilizer, straw, rich topsoil and soft clippings from trees and shrubs. Grass, weeds and kitchen waste may be used in great quantity, as they decay very rapidly. Leaves, hay, sawdust, cornstalks and straw are slower and require a longer decomposition period.
Materials that resist decay or should otherwise not be used are diseased plants (which should be burned), bones, meat, grease, animal fat, grapefruit or orange skins, woody plants, twigs, branches, weeds with ripe seeds and leaves from the oak, beech or pine tree.
The restrictions upon leaves and fruit skins are not mandatory to anyone but the serious gardener. These materials will not ruin the compost pile but may lower its value somewhat. They also require a longer period of time for total decay.
Many people feel that it's easier and safer to compost leaves than to burn them. The trade of fire, smoke and worthless ashes for valuable humus certainly makes good ecological sense. Leaves decompose at a slower rate than other compost, however, and can retard the natural processing of a mixed heap. The solution is to segregate them into a separate pile where—at the end of two years—they'll yield excellent leaf mold.
Vegetable cuttings from the kitchen are one of the easiest substances to compost. Cooked or uncooked, they contribute greatly to the process.
Preparation and Construction of the Compost Pile
The compost pile should be built in a shaded area to lessen its chance of drying out. Remember though, that wood-rotting fungi in wet compost makes it impractical to stack the heap right against trees or any wooden structure.
Form the pile into a compact, regular shape (indiscriminate, strung-out dumping can produce poor humus, insects and other problems), with the top indented to catch and hold rainwater. The sides will naturally slope inward but the degree of slope should be as little as possible, otherwise water will run down the sides and be lost.
Bacteria that thrive on both oxygen and moist (but not damp) conditions are the fastest working composters and both air and water must penetrate the layers of a heap to keep them happy. For this reason a compost pile should not exceed five feet in height.
Best results are obtained by alternating layers of vegetable matter with layers of soil, sod and manure. To hasten decomposition and improve the quality of the compost, add to each layer a sprinkling of ground limestone, phosphate rock, bone meal, blood meal, tankage or sewer sludge. Some folks add special "activators" also but a controlled test at Michigan State University has shown that such activators do not improve composting action at all as long as a pile has plenty of nitrogen in the form of manure, sewer sludge, bone meal, blood meal or other materials rich in this element.
By varying the ratio of soil, rock powder, vegetable and animal matter a compost pile can be given a highly individualistic character and you can use this flexibility to "tailor make" humus for a particular crop. In the beginning, however, any compost is better than no compost at all: Layer whatever you have available into a heap and let nature take its course.
When your pile has reached the desired height (remember the indentation in the top!), cover it with a layer of top soil. Sir Albert Howard, the original developer of today's refined composting techniques, recommends 1/8 inch of urine soaked soil for this covering. If your heap is on a small city lot, you may want to substitute a heavier layer of plain top soil to control moisture and odor.
While your first pile decomposes, you may start another. By having two—or several—at various stages of decay, you'll be assured of a constant supply of humus.
As the materials decompose, the silt will grow smaller. It should be kept moist by occasional watering but this may not be necessary if the indentation on top catches enough rainwater.
After about three months, your compost pile should be "turned" to thoroughly mix the layers, put the outside materials into the middle and allow a fresh supply of air into the center for the aerobic, or oxygen-hungry bacteria. Every time new compost is exposed, it should be covered with soil or, if an alkali humus is preferred, lime. The materials will then decay uniformly.
As a substitute for turning the pile even once, try this: After the three month period, cover your heap with a sheet of black polyethylene and weight the plastic on all sides to prevent it from blowing away. This polyethylene eliminates the necessity of turning and watering the pile and—by holding moisture in and absorbing heat from the sun—encourages anaerobic (air-less) decomposition.
If no new material is added, the compost will be ready for use in about nine months to a year from the time it was "finished".
How to Use Compost in the Garden
The compost can be used when it is crumbly in your hand and has the appearance of dark, rich soil. It is ideal as potting soil for house plants and for starting young seedlings. A small amount added each year to flower beds will help keep them in good condition. In sufficient quantity, it makes an excellent lawn dressing.
For garden use, compost may be applied just as it is taken from the well-rotted heap. In making potting soil or filling greenhouse benches, it's best to screen compost through 1/2 inch mesh wire to remove any stones, sticks, or coarse material. The latter may be used as mulch or as the bottom layer of a new pile.
Decayed compost improves the quality of any soil to which it is added. With compost, sandy soil retains more moisture and heavy clay mellows and becomes easier to handle. The compost helps retain moisture, increases humus content, supplies plant food, allows air to enter the soil, prevents crusting, reduces erosion, controls soil temperatures, lessens evaporation and discourages weeds. It's a heap of help for the gardener.