Urban Orchards : Compost: Nature's Black Magic

Compost: Nature's Black Magic

It may seem like magic – a pile of leaves, grass clippings, pulled weeds and kitchen scraps turns into a wonderful, dark, uniform, organic soil amendment-compost. But making compost doesn't require a magician's tricks, just a little tinkering with the natural decay cycle.

In the soil, microorganisms, nematodes, and earthworms consume organic matter and break it down into similar compounds. They require air, moisture, and heat to do so. The same process happens in a compost pile. It just happens faster (in an active pile) because the microorganisms have a diverse supply of raw materials to digest and optimal conditions for their work.

The Magic Formula
You can make compost one of two ways-by the active method or the passive method. The active method, of course, requires more work. With either method, the first step is to make a compost pile. You can build wooden or concrete block bins or buy a commercially made plastic bin to hold your pile in place. Or you can just layer the materials in a heap. An easy way to keep a passive pile contains is to set up a heavy chicken wire cylinder as a frame.

Follow these simple guidelines for successful composting:: Location: Select a shady, well-drained spot for your pile.; Season: It's best to compost when temperatures are above 50°F. At lower temperatures your pile will not be active, or may freeze. Of course, you can restart the compost pile in spring by turning it and adjusting the moisture content.; Preparation: Clear away sod or other surface cover at the site. Loosen the soil with a spading fork, and put down a base layer of brush or wood chips.; Materials: Materials you can use include garden wastes, grass clippings, kitchen scraps, manure, newspaper, and sawdust. Never include meat scraps or fats, which attract dogs and rodents. It's also best not to add kitchen scraps that are heavy with oil, as oils take longer to break down and can slow the composting process.; Layering: Alternate layers of plant material such as chopped leaves or straw with nitrogen-rich layers of kitchen scraps mixed with manure or blood meal. If you don't have nitrogen-rich materials, don't worry. Your compost will just take longer to finish.; Activating: Add an activator that has microorganisms and growth stimulants to boost your pile's activity. You can use topsoil, fresh manure, or a commercial compost activator such as BioActivator.; Shredding: Shred materials to make better compost more quickly.; Moisture: Keep compost moist, but not wet; it should feel as damp as a squeezed-out sponge. Cover loose piles or open bins with plastic or a heavy canvas so they won't become waterlogged by rain. If your compost is too dry, use water with kelp extract added to moisten it; this will help stimulate biotic activity.; Minerals: Add the fertilizers your garden needs directly to the compost as you add layers of plant material to the pile. It saves a step in your garden work and makes richer humus. Try adding colloidal or rock phosphate and kelp or fishmeal.; Size: Size can vary. A pile 3 feet square heaped 5 feet high can yield almost a ton of compost. The ideal size for an active compost pile is 4 feet by 4 feet by 4 feet.; Aerating: The microorganisms that drive the composting process need air. Fluff or turn the pile regularly to keep microorganisms active, and to prevent the pile from overheating.

Active or Passive?
If you want your compost to stay active, you must turn it every week or so to add oxygen and keep the decomposition rate high. The inside temperature of an active pile can reach 107° F. If you are composting diseased plant material or plants that have seed set, you must keep the pile at or above 160° F to kill disease organisms and weed seeds. Otherwise a range of from 140° F to 150° F is ideal. You can use a compost thermometer to monitor the temperature of the pile. Plan to turn the pile whenever the center of pile exceeds 140° F.

Of course, you can't just flip a pile like a pancake. Turning a pile means mixing and loosening the materials that make up the pile. If you have more than one compost bin, you can turn a pile by forking the material from one bin into another. Moving the pile in this way will let in air and remix the materials, which will stimulate a new flush of microbial activity. If you just have a single loose compost pile, you can turn it by using a spading or manure fork to life material, shake it, and try to redistribute it in the pile.

If you don't want to worry about turning your compost, build a passive pile. A passive compost pile is simply a pile of organic material that is left to sit until the material decomposes slowly over time-usually one to two years. Making leaf mold is an example of this. Most homeowners have passive piles tucked somewhere in the far reaches of their backyards. This approach may not produce as much compost for the garden, but it does work, and at least it's a good method for recycling yard wastes.

Many communities now collect yard waste and compost it en masse. If municipal yard waste is available in your area, it can be an excellent source of organic matter. However, not all municipal programs actually compost the yard waste; some just stockpile it. Keep in mind that unless your municipal maintenance department is turning and monitoring the material to keep it active, it may not be truly composted. If you collect some for your home garden, put it in an active pile to kill off any disease organisms it may contain. Active composting will also help break down pesticide residues that could be in the material.

Computing Compost Coverage
Recommendations for spreading compost or other soil amendments are often given in terms of spreading a layer of a given thickness. But how do you know how much material to spread to end up with such a layer? The ratio to remember is 9 cubic yards of compost per 100 square feet of garden yields a 1-inch thick layer. Here's how to apply the ratio to your garden.: 1. First measure the area you want to cover with compost and determine the total square footage.; 2. Divide by 100.; 3. Multiply by the thickness of the layer you want to spread (in inches).; 4. Multiply that number by 9. This will tell you how many cubic feet of compost you need.

A handy “measuring cup” for compost is a 30-gallon garbage can. It holds about four cubic feet (or about 50 pounds) of finished compost. You can also measure the volume of your garden cart and use it as your measuring device.

Excerpted with permission from Rodale's Chemical-Free Yard & Garden. To order, call 1-800-848-4735 or write to 33 E. Minor St., Emmaus. PA 18098.