Making Compost from Yard Waste
9 August 2006
Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580 fax: 434.872.4578
Compost is one of the most valuable resources for enriching your landscape and it is virtually free. The leaves you rake, the grass you mow, and the branches you trim are some of the ingredients you can use to make compost. Finished compost is dark and has a pleasant smell. It is produced when bacteria and fungi break down organic matter, such as garden, lawn, and kitchen waste. You can use it throughout your landscape by tilling it into gardens and flowerbeds, adding it to the soil when renovating your lawn, or sieving it and using it in potting soil.
A compost bin is not needed to make compost but if you plan to produce it regularly, consider a permanent compost bin. For convenience and aesthetics, you can choose from numerous commercial compost bin designs or construct your own.
Some gardeners build separate bins for each stage of the compost process. One for fresh plant refuse, another for the actively composting pile, and a third for the finished compost. When building your own bin, keep one side open for easy access. Also, leave spaces between blocks or planks for aeration. Air is essential to the rapid decay of organic materials.
The size of the compost pile determines how effective it will be. Piles smaller than 27 cubic feet (3x3x3) do not hold sufficient heat for the composting to be effective and piles larger than 125 cubic feet (5 x 5 x 5) do not allow sufficient oxygen to reach the center. Be sure your compost pile is a manageable size.
Here are a few keys to good composting.
- The carbon/nitrogen ratio: A mixture of dry leaves, sawdust, or other sources of carbon combined with manure, green plants, or fertilizer for nitrogen (approximately 4:1 by volume).
- The presence of microorganisms: A few shovels full of rich garden soil or compost will supply these.
- The moisture level: The pile should have the moisture of a well-squeezed sponge. Add water as needed.
- The oxygen level: A compost pile should be turned periodically to promote decay of its contents. Turning the pile adds oxygen, so the more you turn it, the faster it breaks down.
- The particle size: The finer the particle size, the more surface there is for microorganisms to work. Shredding leaves and larger materials generates compost faster.
Locate your compost pile on a well-drained site. Your pile can be built gradually in layers and then turned to mix. Or if you have sufficient material, it can be mixed and blended at one time. To ensure good aeration and drainage, put down a three-inch layer of coarse plant material, such as small twigs or chopped corn stalks, or a wooden pallet. Next, add about eight to ten inches of leaves or other dry organic wastes from your landscape and/or kitchen. Do not use meat waste as it attracts animals. Provide nitrogen for compost-promoting microorganisms by adding two to three inches of fresh grass clippings or fresh manure. If fresh nitrogen sources are unavailable add about one-third of a cup of synthetic fertilizer (36-0-0) per 25 square feet of surface area. If no soil is included in your compost material, add a sprinkling of soil or a compost starter to each layer to inoculate the pile with microorganisms. Moisten the pile as you add leaves and other dry material.
Mix the materials thoroughly. Shape the pile so its center is lower than its sides, to help water flow into the pile. Keep the pile moist, but not soaking wet. Within a few days, it should heat up. If not, it may lack nitrogen or moisture. If the pile emits an ammonia smell, it is too wet or too tightly packed for oxygen circulation; turn the heap and add coarse material to increase air space. Once a month, turn the pile with a pitchfork, putting the outside materials on the inside and vice versa.
The plant materials should decompose into compost within five months in warm weather, longer under cool or dry conditions. The center of the pile should reach 160 degrees F to kill most weed seed, insects and their eggs, and disease organisms. It is best to not include weed seed and diseased plant material if possible. Composting may be completed in one or two months if the materials are shredded, kept moist, and turned several times to provide good aeration. Spread it in the garden and dig or till it under to offer your soil and plants renewed vigor.
Compost improves the structure of soil. With the addition of compost, sandy soils hold more water, and clay soils drain faster. Compost reduces soil erosion and water run-off. Plant roots penetrate compost-rich soil easier and hold the soil in place. Water can run down into lower soil layers, rather than puddle on top of the ground and run off. Compost provides food for earthworms, soil insects, and beneficial microorganisms. Compost assists the soil in holding nutrients, thus lessening the need for chemical fertilizers and preventing the leaching of nitrogen into water. Compost promotes healthy plants, which are less susceptible to diseases and insect pests, reducing the need for pesticides.
This fall we are offering Master Gardener training in Greene County. Beginning in January, Virginia Cooperative Extension may be offering Master Gardener training in Albemarle, Fluvanna, Nelson, & Louisa Counties, depending on the level of interest. For more information, call your local Virginia Cooperative Extension office.
For more information about these and other landscape gardening topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.