by Dick Christensen
Colorado State University Cooperative Extension Master Gardener
Following Mother Nature’s example, Colorado gardeners can make compost easily. As a soil amendment, compost improves soil structure and increases soil tilth, fertility, water holding capacity, aeration and drainage. To conserve moisture or develop a landscape requiring less water, it is essential to have soil with good water-retention. In Colorado, a third or more of landfill waste is organic yard refuse during the growing season. Home composting of yard and garden trimmings reduces the burdens on landfills and returns these organic material to the soil.
How to make compost
Step 1 - Site location: Try to locate the compost pile close to where it will be used, without offending neighbors. Select a site that is convenient for adding materials and removing compost, yet one which does not detract from the landscape. The compost pile should be exposed to at least six hours of sunlight a day. The pile will do best in the heat of partial sunlight, but away from drying winds. Water should be readily available. Good drainage is also important, since standing water can slow the decomposition process.
Step 2 - Compost container selection: Structures aren’t necessary for composting but do prevent wind and animals from carrying away plant wastes. Many containers are suitable, provided that they resist decay, allow airflow and are accessible. Most compost containers fall into one of these categories: heaps (simple stacked piles), hoops (caged enclosures), bins (boxed enclosures) and barrels (drum enclosures).
Step 3 - Raw materials selection: Yard and garden debris, kitchen wastes such as vegetable scraps, coffee grounds and eggshells and other organic materials are suitable for composting. If it can rot, it will compost. Green material, like leaves, grass clippings and soft young weeds rot quickly. They work as 'activators', getting the composting started. Older and tougher plant material decomposes more slowly. Woody items decay very slowly; they are best omitted or chopped or shredded first. For best results, use a mixture of ingredients.
Traditional composting includes soil as an ingredient. Large amounts of soil add unnecessary weight. While soil can serve as a source of microbes to “inoculate” plant wastes, research has found that microorganisms which break down plants also are present on the surface of leaves and stems. It is natural for some soil to cling to uprooted plants. There is no advantage in adding compost starters or inoculums to compost piles.
To make compost without soil, alternate green and brown types of shredded plant materials in six- to eight-inch layers. Layering helps compost reach the correct nitrogen balance. Use equal parts by volume of dry and green plant materials in the overall mix. Add water to the compost after every few layers of material. If the plant materials are dry and no green material is available, add a small quantity of blood meal or a commercial nitrogen fertilizer without weed killers.
Do not add meat scraps, bones, grease, whole eggs, or dairy products to the compost pile because they are slow to decompose, will cause odors, and can attract rodents. Due to the possibility of disease transmission, human, dog, and cat feces should not be placed in compost piles. Diseased plant material or weeds that have gone to seed also are undesirable.
Step 4 - Aeration: Composting consumes large amounts of oxygen, particularly during the initial stages. If the supply of oxygen is limited, the composting process may turn anaerobic, which is a much slower and more odorous process. Lifting and turning the materials with a pitchfork or a mechanical aerator may replenish oxygen levels. Try to move drier materials from the outside of the pile into the center. Weekly turning can produce compost in a shorter time period. With the right moisture level and combination of materials, regular turning will produce compost in about four to six months. Without turning, composting may take six months to two years. Aeration is generally a key factor affecting the time necessary to produce finished compost.
Step 5 - Keeping it moist: Moisture is necessary to support the metabolic processes of microorganisms. Composting materials should be kept moist. As a rule of thumb, materials are too wet if water can be squeezed out of a handful of compost and too dry if the handful does not feel moist to the touch. If the compost pile is too dry, the process slows down. If the pile is too wet, water will displace much of the air in the pore spaces of the composting materials, limiting air movement and leading to anaerobic conditions. Moisture content generally decreases as composting proceeds; so you may need to periodically add water to the compost. Many people cover their compost with plastic to prevent the outer layers from drying too much. Remove covers periodically to add more water and plant material and to aerate.
Step 6 - Temperature: Composting will essentially take place within two temperature ranges, known as mesophilic (50-105 degrees F) and thermophilic (over 105 degrees F). Keeping temperatures between 110 and 150 degrees destroys more pathogens and weed seeds in the compost.
Step 7 - Curing: Finished compost is dark, crumbly, and has a rich, earthy, inoffensive odor. Curing refers to finished compost left in a pile undisturbed for up to one month, allowing any final chemical and decomposition reactions to occur. Curing ensures that the composting process is indeed complete and that potential problems are minimized. Remember that compost is a soil amendment, not a fertilizer. It contains limited plant nutrients.
Compost is an excellent, inexpensive way to increase the productivity and workability of soil. It reduces and recycles yard waste and produces a valuable soil amendment. Help the garden, the environment, and your bank account by composting lawn and garden waste.
For more information see Fact Sheet # 7.212 – Composting Yard Waste. You may also call Planttalk Colorado at 1-888-666-3063 and request topics number 1612, 1613, 1623, 1614, 1615 and 1622 on composting. Planttalk Colorado is a 24-hour toll-free automated phone service that provides you with reliable, timely information on a variety of horticultural topics.
Helpful Web Sites:
Q: Is there something else to use besides turf grass?
A: Ground cover plants are good alternatives to turf grasses in some landscape locations. They provide a variety of textures and color, help reduce soil erosion and can serve as a transition between turf areas and shrub or flower borders. Consider using ground cover plants especially where watering and mowing of turf grasses may be difficult or higher maintenance. Consider non-turf ground cover plants for: narrow strips between sidewalks and curb or structures; steep slopes that are impractical to mow; hot, dry areas along south and west exposures of walls or fences; deeply shaded areas beneath trees, shrubs or along north sides of walls and fences and in foundation plantings in front of low windows. Ground covers can enhance the beauty of shrub borders. Ground cover plants also are very useful in breaking up the monotony of areas previously covered with gravel.
Q: Can diseased plants be safely composted?
A: Most often the answer is no. If your compost pile reaches temperatures in the range of 122? F to 140? F, most of the disease organisms should be killed. (A temperature probe can be used to monitor compost pile temperatures.) If you are not sure if your compost pile is reaching these high temperatures, it is a good idea to discard the material by bagging it.
Remove onion and garlic bulbs from the soil. Separate them after drying and plant larger bulbs in prepared area for the next season.
Clear garden vegetation after the first frost and place it in your compost. Amend soil and till and you are ready to plant early next spring.
Prevent weed infestation by eliminating them before they mature and seed. Weeds consume a large amount of water and often out-compete the more desirable plants.
The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.
Gardening and Insect Fact Sheets are available on-line by clicking HERE.
Return to Master Gardener Articles