Composting is a process in which organic substances are reduced from large volumes of rapidly decomposable materials to small volumes of materials which continue to decompose slowly. In this process, the ratio of carbon to other elements is brought into balance, thus avoiding temporary immobilization of nutrients. One of the many benefits of adding compost to the soil is that the nutrients in it are slowly released to the soil and are then available for use by plants.
Compost can range from passive – allowing the materials to sit and rot on their own – to highly managed. Whenever you intervene in the process, you’re managing the compost. How you compost is determined by your goal. If you’re eager to produce as much compost as possible, you may opt for a more hands-on method of composting.
Otherwise, passive composting involves the least amount of time and energy on your part. This is done by collecting organic materials in a freestanding pile. It might take a long time (a year or two), but eventually organic materials in any type of a pile will break down into finished compost. More attractive than a big pile of materials sitting in your yard is a 3-sided enclosure made of fencing, wire, or concrete blocks, which keeps the pile neater and less unsightly. Add grass clippings, leaves, and kitchen scraps (always cover these with 8″ of other material). The pile will shrink quickly as the materials compress and decompose. Wait a year or two before checking the bottom of the bin for finished compost. When it’s ready, shovel the bottom section into a wheelbarrow and add it to your garden beds. Continue to add greens and browns to have a good supply of finished compost at the ready. After the first few years, most simple piles produce a few cubic feet of finished compost yearly.
Managed composting involves active participation, ranging from turning the pile occasionally to a major commitment of time and energy. If you use all the techniques of managing the pile, you can get finished compost in 3-4 weeks. Choose the techniques that reflect how much you want to intervene in the decomposition process and that will be a function of how fast you want to produce compost.
The speed with which you produce finished compost will be determined by how you collect materials, whether you chop them up, how you mix them together, and so on. Achieving a good balance of carbon and nitrogen is easier if you build the pile all at once. Layering is traditional, but mixing the materials works as well.Shredded organic materials heat up rapidly, decompose quickly, and produce uniform compost. The decomposition rate increases with the size of the composting materials. If you want the pile to decay faster, chop up large fibrous materials.
The temperature of the managed pile is important – it indicates the activity of the decomposition process. The easiest way to track the temperature inside the pile is by feeling it. If it is warm or hot, everything is fine. If it is the same temperature as the outside air, the microbial activity has slowed down and you need to add more nitrogen (green) materials such as grass clippings, kitchen waste, or manure. Too much water is just as detrimental as the lack of water. In an overly wet pile, water replaces the air, creating an anaerobic environment, slowing decomposition.
Air circulation is an important element in a compost pile. Most of the organisms that decompose organic matter are aerobic – they need air to survive. There are several ways to keep your pile breathing. Try not to use materials that are easily compacted such as ashes or sawdust, without mixing them with a coarser material first. People who build large piles often add tree branches or even ventilation tubes vertically into different parts of the pile, to be shaken occasionally, to maximize air circulation.
A more labor-intensive way to re-oxygenate the pile is to turn the pile by hand, using a large garden fork. The simplest way is to move the material from the pile and restack it alongside. A multiple-bin system makes this efficient, in that you only handle the material once. Otherwise, you can put the material back into the same pile. The object is to end up with the material that was on the outside of the original pile, resting in the middle of the restacked pile. This procedure aerates the pile and will promote uniform decomposition.
Vermicomposting, or worm composting, is different than traditional composting. Worm composting is a process that uses red earthworms, also commonly called redworms, to consume organic waste, producing castings (an odor-free compost product for use as mulch), soil conditioner, and topsoil additive. Naturally occurring organisms, such as bacteria and millipedes, also assist in the aerobic degradation of the organic material.
Finished compost is dark brown, crumbly, and is earthy-smelling. Small pieces of leaves or other ingredients may be visible. If the compost contains many materials which are not broken down, it is only partly decomposed. This product can be used as mulch, but adding partly decomposed compost to the soil can reduce the amount of nitrogen available to the plants. The microorganisms will continue to do the work of decomposing, but will use soil nitrogen for their own growth, restricting the nitrogen’s availability to plants growing nearby.
Compost serves primarily as a soil conditioner, whether it’s spread in a layer on the soil surface or is dug in. A garden soil regularly amended with compost is better able to hold air and water, drains more efficiently, and contains a nutrient reserve that plants can draw on. The amended soil also tends to produce plants with fewer insect and disease problems. The compost encourages a larger population of beneficial soil micro organisms, which control harmful micro organisms. It also fosters healthy plant growth, and healthy plants are better able to resist pests.
One inch thick is enough to spread on your garden beds. Compost continues to decompose, so eventually the percentage of organic matter in the soil begins to decline. In northern climates, compost is mostly decomposed after two years in the soil. In southern climates, it disappears even faster and should be replenished every year. To bolster poor soil with little organic matter, spread 2 to 3 inches of compost over a newly dug surface. Then work the compost into the top 6 inches of earth.
Some people recommend late fall as a good time to spread compost over a garden bed, and cover it with a winter mulch, such as chopped leaves. By spring, soil organisms will have worked the compost into the soil. Others recommend spreading compost two weeks before planting time in the spring. There is really no wrong time to spread it. The benefits remain the same.
If your supply of compost is really limited, consider side-dressing, a way to use compost sparingly by strategically placing it around certain plants or along certain rows. This is best done in late spring and early summer so that the rapidly growing plants can derive the maximum benefit from the compost. To side-dress a plant, work the compost into the soil around the plant, starting about an inch from the stem, out to the drip line, taking care not to disturb the roots. For shallow rooted plants, leave the compost on the soil surface. A 2″ layer works best when left on top.
Compost mulch can benefit trees and shrubs just as it does other plants. Spread a ½” to 1″ layer of compost on the bare soil under the tree as far as the drip line. Then cover with a 2-3″ layer of some other kind of organic mulch, such as chopped leaves or pine needles. The mulch will hold the compost in place and keep it from drying out.Compost is the ultimate garden fertilizer. It contains virtually all the nutrients a living plant needs and delivers them in a slow-release manner over a period of years. Compost made with a wide variety of ingredients will provide an even more nutritious meal to your growing plants.
Compost is the best material available to enliven your soil no matter where you live. Growers around the world will testify that healthier soil grows healthier plants that naturally resist disease, insects, and other environmental pressures. Adding compost to your plants is a long-term investment – it becomes a permanent part of the soil structure, helping to feed future plantings in years to come.