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Managing Yard Wastes: Clippings and Compost-کمپوست:   Revised 10/02 Purdue University Cooperative Extension Service Page 1 of 3   Solid Waste Management Series . ID-182-W   Department of Horticulture   Purdue University Cooperative Extension Service • West Lafayette, IN   Managing Yard Wastes: Clippings and Compost   B. Rosie Lerner   Turning Trash to Treasure   Yard waste materials such as grass clippings, leaves,   and yard trimmings make up approximately 10% (by   volume) of the municipal waste stream, according to   Indiana’s Department of Environmental Management.   Yard waste can account for 50% or more of residential   solid waste during the active growing season.   Although this waste is biodegradable, landfills do not get   the oxygen and water needed for breakdown. Landfills   are constructed to prevent movement of air and moisture   in order to protect the surrounding environment. These   materials can be better put to use enhancing our gardens   and landscapes.   Some communities have established municipal   composting facilities to efficiently manage large quantities   of yard wastes. But by reducing the amount of yard waste   generated and recycling the rest, gardeners can have a   great impact, both economically and ecologically.   Reducing Yard Wastes   Leaving grass clippings on the lawn rather than bagging   for disposal is an excellent way to dramatically reduce   yard waste. The amount of grass clippings generated   from a given lawn varies, depending on the grass species,   weather, fertilization program, and yard size. One   estimate indicates that 5,000 square feet of lawn generates   about 1 ton of clippings per year!   Grass clippings left on the lawn are not harmful to the turf   if it is mowed at the proper height and frequency. In fact,   the clippings will return some nutrients back to the soil,   reducing fertilizer requirements. Contrary to popular   belief, grass clippings do not contribute to thatch buildup   because they break down quite rapidly. Thatch is composed   of dead, decomposing roots, and underground   stems.   Maintain the lawn at a height of about 3 inches, removing   no more than 1/3 or the grass plant each time. This will   likely mean mowing more often than once a week, but   mowing time is greatly reduced when clippings are not   collected. Mow only when the lawn is dry to prevent   clippings from matting down. If the lawn is excessively tall   when mowed, you should remove the clippings and either   use as a mulch or add to a compost pile.   Recycling Yard Wastes   Composting is a naturally occurring process that breaks   down organic materials into a soil-like material. Finished   compost is an excellent soil amendment that improves   soil structure as well as adds some nutrients. All organic   materials will break down eventually, if given the proper   environmental conditions. Gardeners can speed up the   composting process with proper management of the   materials and environment of the compost system.   Ingredients of Compost   The basic ingredients for successful composting include   organic materials, microorganisms, and the proper   balance of carbon to nitrogen, water, and oxygen. Let’s   look at each of these more closely.   Organic materials for composting include discarded   garden plants, grass clippings, tree leaves, and plant   trimmings. The smaller the particle size, the faster the   organic materials will break down. Materials which have   been chopped or shredded will compost more quickly.   Kitchen wastes such as vegetable and fruit scraps, egg   shells, and coffee or tea grounds can also be added.   These materials should be buried in the center of the   compost pile to avoid attracting insects, rodents, and   neighborhood pets.   Some organic materials are best left out of the compost   pile because of possible health hazards or attractiveness   to pests. Because of the danger of disease transmission,   human and pet feces should not be composted. Meat   scraps, bones, and fats will likely attract rodents and   other unwanted visitors.   Less experienced composters should avoid materials   Page 2 of 3 Purdue University Cooperative Extension Service Revised 10/02   Solid Waste Management Series . ID-182-W   heavily infested with weed seeds, insects, and disease   organisms. Although a properly managed compost pile   should generate enough heat in the center to kill most of   these pests, ensuring uniform heat may be difficult,   particularly in a small compost pile.   Microorganisms (microbes) such as bacteria and fungi   are responsible for breaking down the organic materials   in yard waste. Although commercially packaged compost   starter is available, adding a little soil or finished compost   will supply all the microbes you need for composting.   Microorganisms require a proper environment to work   efficiently. Any factor which affects the microbial population   will also affect the rate of decomposition.   Nitrogen is needed by the microbes in order to break   down and use the carbon found in organic materials. The   ratio of carbon to nitrogen in the compost pile will affect   the rate of decomposition. If the carbon content is too   high, decomposition will be slow. If the nitrogen content is   too high, ammonia gas can be given off, creating foul   odors.   The ideal ratio of carbon to nitrogen is approximately   30:1. Table 1 shows the carbon to nitrogen ratios of   various organic materials. Sawdust has a high C:N ratio,   while animal manures have a low C:N ratio. The ideal   ratio for composting can be achieved by combining high   and low carbon materials, such as dry tree leaves and   fresh grass clippings. Another method is adding a   nitrogen source such as livestock manures or commercially   packaged fertilizer to high carbon materials.   Water is also needed for efficient microbial action and   uniform heating of the compost. Apply water as needed if   rainfall is lacking. Compost with optimum moisture   content should resemble that of a moistened sponge that   has the excess water squeezed out.   Oxygen is required for efficient decomposition and to   prevent foul odors. Breakdown occurs more slowly when   oxygen is lacking, and foul odors from fermentation will   result. Turning and mixing the pile at least once or twice   a month will add oxygen from the air into the center of the   pile. Mixing the compost also helps bring the outer   materials to the center for heating and faster decomposition.   Lime is generally not needed in most compost piles.   Although lime is recommended by some gardening books   to "sweeten" (make alkaline) the compost pile, several   studies indicate that finished compost is already slightly   alkaline. Adding lime may lead to production of ammonia   gas, which allows nitrogen to escape from the pile and   causes foul odors. Wood ashes are very highly alkaline   and should only be added in very small quantities, if at   all.   Containing Compost   Compost can be constructed in open piles, but it is   probably more easily managed in some type of structure.   Many types of containing materials can be found around   the home or at a hardware supplier. Examples include   wooden pallets, metal mesh wire, and cinder blocks.   Molded plastic bins such as those with a turning crank   and aeration holes are also available for relatively small   composting operations.   A three-bin container is ideal for managing compost   (Figure 1). One bin is for actively composting materials.   One bin remains empty to allow the compost to be turned   over more easily. The third bin is used for holding plant   materials until the current compost is finished.   Locate the compost pile close enough to the house so it   is readily accessible but out of the way of other activities.   Choose a shady spot with protection from the wind to   avoid excessive heating and drying.   Managing Compost   To achieve a good balance of materials, construct   compost piles in layers, alternating yard wastes; a   nitrogen source, if needed; and soil (or finished compost)   (Figure 2). The base layer should consist of 6-10 inches   of organic materials, with coarser, dry materials on the   bottom. If needed, follow with a nitrogen source such as   3'-5"   3'-5"   4'-5"   Empty Active Holding   Figure 1. A three-bin   container for managing compost.   Table 1. Approximate carbon to nitrogen (C:N) ratio of   various materials used in municipal and backyard   composts.*   Material C:N ratio   (wt:wt)   Livestock manure 10 to 30:1   Table scraps 11 to 15:1   Alfalfa 12 to 19:1   Grass clippings 15 to 25:1   Fruit wastes 25 to 45:1   Sugarbeet 30 to 40:1   Leaves 40 to 80:1   Paper 200 to 800:1   Sawdust 100 to 750:1   Wood 200 to 1300:1   *Adapted from Composting and Mulching: A Guide to   Managing Organic Yard Wastes. University of Minnesota   Extension Service Bulletin BU-03296.   Revised 10/02 Purdue University Cooperative Extension Service Page 3 of 3   Solid Waste Management Series . ID-182-W   1-2 inches of animal manure or approximately 1 cup of a   balanced, low-analysis fertilizer (such as 12-12-12), per   25 square feet of compost surface area. The next layer   should be approximately 1 inch of soil or finished compost.   Repeat layers as organic materials are added.   Water each layer as it is needed, and check the pile   occasionally for watering needs.   The center of a properly managed compost pile will   generate heat as the microorganisms break down the   organic matter. A good-sized compost heap, approximately   4-5 feet in diameter and 4-5 feet deep, should   reach 130° to 160° F in the center.   Turn the pile with a pitchfork or shovel at least once or   twice a month to keep the materials supplied with oxygen   and to bring outer contents to the center for heating.   Small amounts of organic materials can be added to   actively composting piles, but it’s best to start a new pile   when compost becomes too tall to work by hand.   Using Finished Compost   Compost can be ready to use in as soon as a month or   as long as a year, depending on how well the pile is   constructed and tended. Finished compost should look   much like a uniform potting soil, with no indication   remaining of what materials originally went into the pile.   Compost can be used as a soil amendment in the garden   to add some nutrients, but its primary advantage is that of   improving soil structure. Adding compost increases   water-holding capacity, aeration, and nutrient exchange   sites in the soil.   Compost can also be used as an organic media in potting   soil or for starting seeds of garden plants. Finished   compost is free of pests and weed seeds only if it has   been properly mixed and uniformly heated. To be sure   your compost is free of pests, pasteurize it by heating in   a conventional oven to 180° F for 30 minutes. Be sure   the compost is slightly moist to ensure uniform heating.   Compost is also useful as a garden mulch to conserve   soil moisture, cool the soil, and discourage weeds. And it   can be used to cover seeds as they are planted, to   prevent crusting in heavy soils.   Compost is an inexpensive and ecologically sound   Less coarse organic material   Coarse organic material   Soil or finished compost   Manure or fertilizer   Figure 2. Compost constructed in layers.   Because of possible injury to desirable plants,   clippings from lawns treated with weed killer should   not be used as mulch for at least 8 weeks after the   herbicide is applied. Most commonly used lawn   herbicides will break down in that time, but some do   take several more months to a year to degrade.   Leaving these clippings on the lawn is the best   method of disposal.   Pesticides are biodegradable and are dependent on   the same environmental factors as composting yard   wastes: microorganisms, temperature, water, and   oxygen. Several studies have shown that   composting decreases the concentrations of most   modern-day pesticides to levels below EPA regulations.*   * Mechanisms of Pesticide Degradation in Compost   By Craig Coker, Composting Specialist   North Carolina Division of Pollution Prevention &   Environmental Assistance   http://www.cra-recycle.org/CCC/techcornerindex/   techcornerarticles/TCpesticidedegradation.htm   A citizen education program called "Don’t Bag It"   was piloted in Ft. Worth, Texas to encourage   citizens to reduce yard waste. The 184 residents   participating saved the city $60,000 in garbage   collection costs and saved themselves a total of   $22,000 by purchasing fewer plastic bags for   disposal. Participants reduced the average time for   mowing by more than 30 percent, although they did   mow more frequently. And, of course, the local   landfill saved considerable waste space.   "Don’t Bag It" Lawn Care Plan, Texas A&M   Extension Service   http://aggie-horticulture.tamu.edu/extension/   homelandscape/dontbag/dontbag.html   For more information on the subject discussed in this   publication, consult your local office of the Purdue University   Cooperative Extension Service.   It is the policy of the Purdue University Cooperative Extension Service, David C. Petritz, Director, that all persons shall have equal opportunity and access to programs and facilities   without regard to race, color, sex, religion, national origin, age, marital status, parental status, sexual orientation, or disability. Purdue University is an Affirmative Action employer.   This material may be available in alternative formats. http://www.agcom.purdue.edu/AgCom/Pubs/menu.htm   method of managing yard waste and producing an   excellent gardening tool. Composting will help you   recycle your garden wastes, improve your soil, and   reduce disposal costs             www.ake.blogfa.com                          www.ake.blogfa.com