Compost is a nutrient-rich and crumbly blend of partially decomposed organic material that improves soil structure. Most gardeners don’t start with great soil. Whether yours is hard and compacted, sandy, stony, heavy, or wet, adding compost will improve its texture and water-holding capacity and fertility. Your soil will gradually become fluffy and chocolaty brown — the ideal home for healthy plants. Compost will help your soil remain rich and productive by replenishing the nutrients that are consumed each growing season. Unlike organic or inorganic fertilizers, which need to be applied at the right time and in the right amount, compost can be applied at any time and in any amount.
MICROORGANISMS AT WORK
The microorganisms, enzymes, vitamins, and natural antibiotics that are present in compost help prevent many soil pathogens from harming your plants. Earthworms, millipedes, and other macroorganisms tunnel through your soil, opening up passageways for air and water to reach your plants’ roots.
Organic matter is transformed into compost through the work of microorganisms, soil fauna, enzymes, and fungi. When making compost, your job is to provide the best possible environment for these beneficial organisms to do their work. If you do so, the decomposition process works very rapidly. If you don’t, decomposition will still happen, but it may take from several months to several years. The trick to making an abundance of compost in a short time is to balance the following four things:
- Carbon-rich materials are the energy food for microorganisms. They are dry, tough or fibrous, and tan or brown in color, such as dry leaves, straw, rotted hay, sawdust, shredded paper, or cornstalks. (Do not use meat, poultry, dairy products, or heavily salted foods.)
- High-nitrogen materials provide the protein-rich components that microorganisms require to grow and multiply. These include freshly pulled weeds, fresh grass clippings, over-ripe fruits and vegetables, kitchen scraps, and other moist green matter.
- Moisture is very important for the composting process; however, too much moisture will drown the microorganisms, and too little will dehydrate them. A general rule of thumb is to keep the material in your compost pile as moist as a well-wrung sponge. Using an enclosed container or covering your pile with a tarp will make it easier to maintain the right moisture level.
- Oxygen is required for microorganisms to do their work most efficiently. When your pile is first assembled, there will probably be plenty of air between the layers of materials. But as the microorganisms begin to work, they will start consuming oxygen. Unless you turn or in some way aerate your compost pile (see below), the microorganisms will run out of oxygen and become sluggish.
DO I NEED A RECIPE?
Microorganisms and other soil fauna work most efficiently when the ratio of carbon-rich to nitrogen-rich materials in your compost pile is approximately 25:1. More simply, if you use about three times as much “brown” materials as “green” materials, you’ll be off to a great start.
HEAT AND MICROBES
Heat is a by-product of intense microbial activity. It indicates that the microorganisms are munching on organic matter and converting it into finished compost. The temperature of your compost pile does not affect the speed or efficiency of the decomposition process. But temperature does determine what types of microbes are active.
Psychrophiles work in cool temperatures. As they begin to digest some of the carbon-rich materials, they give off heat, which causes the pile temperature to rise. When it warms to 60 to 70 degrees, mesophilic bacteria take over. They are responsible for the majority of the decomposition work, and can raise the temperature to about 100 degrees. Then thermophilic bacteria kick in and can raise the temperature high enough (155 degrees) to sterilize the compost and kill disease-causing organisms and weed seeds.
TO TURN OR NOT TO TURN
Unless speed is a priority, frequent turning is not necessary. Turning increases oxygen flow for the microorganisms, and blends undecomposed materials into the center of the pile. If you are managing a hot pile, you’ll probably want to turn your compost every three to five days, or when the interior temperature dips below about 110 degrees. You can keep your pile well aerated without the hassle of turning with one of these methods:
- Build your pile on a raised wood platform or on a pile of branches.
- Make sure there are air vents in the sides of your compost bin.
- Put one or two perforated four-inch plastic pipes in the center of your pile.
Home composting can reduce your garbage bill and waste in the landfill as well as produce a resource that takes garden and house plants to a new level of health and productivity.