Composting

Biological Process
The compost pile is really a teeming microbial farm. Bacteria, the most numerous and effective composters, are the first to break down plant tissue. Fungi and protozoans soon join the bacteria and, somewhat later in the cycle, centipedes, millipedes, beetles and earthworms do their parts.

Any plant material growing in your yard is potential food for these tiny decomposers. Microorganisms use the carbon in leaves or woodier wastes as an energy source. Nitrogen provides the microbes with the raw element of proteins to build their bodies.

Everything organic has ratio carbon to nitrogen (C:N) in its tissues. The following table can help you judge the ratio of your compost ingredients.

Carbon : Nitrogen Ratios

A C:N ratio of 30:1 is ideal for the activity of compost microbes. This balance can be achieved by mixing two parts grass clippings with one part leaves. This combination is the "backbone" of most compost systems. Do not use meat scraps, bones, fatty materials, or other kitchen wastes.

Surface Area
The more surface area the microorganisms have to work on, the faster the materials decompose. Chopping your garden waste with a garden tool, or running them through a shedding machine or lawnmower, will speed their decomposition.

Volume
A large compost pile will insulate itself and hold the heat of microbial activity. Its center will be warmer than its edges. Piles smaller than 3 feet cubed (27 cu. ft.) will have trouble holding this heat, while piles larger than 5 feet cubed (125 cu. ft.) don't allow enough air to reach the microbes at the center. These proportions are of importance only if your goal is a fast, hot compost. Slower composting requires no exact proportions.

Moisture and Aeration
All life on Earth, including compost microbes, needs a certain amount of water and air to sustain itself. Microbes function best when the compost heap has many air passages and is about as moist as a wrung out sponge (60-70%). Extremes of sun or rain can adversely affect this moisture balance.

How to Make Compost

Remove the grass and sod cover from the area where you will construct your compost pile to allow materials direct contact with soil microorganisms. The following "recipe" for constructing your compost heap is recommended:

1. 1st layer - 3"-4" of chopped brush or other course material on top of the soil surface allows for better air circulation around the base of the heap.
2. 2nd layer - 6"-8" o mixed leaves, grass clippings, or sawdust. The materials should be sponge damp.
3. 3rd 1ayer - 1" of soil or finished compost serves as an inoculate by adding microorganisms to the heap. This layer is not necessary since the inoculum needed for composting is normally present; however, it will help to speed the composting process.
4. 4th layer - small amounts of commercial fertilizer may be added to provide the nitrogen needed by microorganisms. Water may also be added if the compost is dry.

Repeat steps 1 through 4 until the bin is almost full. The top of the compost pile should be level or have a slight basin to catch rainwater. A properly made compost pile will reach a temperature of 140 F to 160 F within 4-5 days. At this time you will notice the pile "settling", a good sign that the compost pile is working properly.

After one to two weeks, aerate the compost by forking or turning the materials into a new pile, turning the outside of the old heap into the center of the new pile. Add water if necessary. The aeration of your compost pile is necessary to prevent the anaerobic microorganisms from producing serious nuisance conditions. The byproducts from anaerobic decomposition include fatty organic acids, aldehydes, alcohols, and hydrogen sulfide.

Hydrogen Sulfide, for example, is a very reactive gas and will combine with partly degraded organic matter to form dark colored offensive compounds associated with the odor of the decomposition.

Check the internal temperature regularly; when the temperature decreases substantially, (usually 1 to 2 weeks) turn the pile. The compost should be ready to use within 3 to 4 months.

Compost is ready to use when it is dark, brown, crumbly, and earthy smelling. Let it stabilize for a few extra days, then screen it through a 1/2 inch screen if you want a finer product. For garden and flower bed apply 1 to 3 inches of compost and work it in. The finished product should be stable for storage.

Snow Fence Bin
Bins made with prefabricated snow fencing are popular because they are simple to make and easy to move and store. To build this bin, buy the appropriate length of prefabricated fencing and fasten to two-by-fours (2x4s) used for the comers.

Woven Wire Bin
One easy-to-make, economical container requires only a length of woven wire fencing or snow fence. Multiply the diameter you want for the compost pile by 3.2 to determine the length of fencing to buy. Fasten the ends with wire or with three or four small chain snaps (available at any hardware store) to make a circle.

Block or Brick Bin
Compost bins can be made with bricks or cement blocks. Just lay the blocks without mortar leaving spaces between each block to permit aeration. Stack them to form three sides of a square container. This type of bin is sturdy, durable and easily accessible.

Wooden Bin
Covered wooden bins allow convenient protection from pests and heavy rains. Construct bins with removable fronts or sides so that materials can be easily turned. Old wooden pallets can be used for construction. Wire mesh can be used on the sides to increase air flow.

Prefabricated compost bins can be purchased through most gardening catalogues.

Turning Bins
This is a series of three or more bins that allows you to make compost in a short time by turning the materials on a regular schedule. Turning bins are most appropriate for gardeners with a large volume of yard waste and the desire to make a high quality compost. You can also turn your compost with only one bin. Simply remove the bin from around the pile when it's time to turn it, set up the empty bin nearby, and fork the material back into it.