1、CompostingA T H O M ER o b e r t R y n k thatis, it requires oxygen. The desired decomposers need oxygen towork their magic. The oxygen consumed during composting must 5be continually replaced by aeration (air flow through the materials).Good aeration is encouraged by placing bulky composting ingred
2、i-ents in the pile to create pathways for air movement, and by“turning” the materials to loosen and mix them. If oxygen becomesscarce, anaerobic decomposition takes place. Anaerobic decom-position is undesirable in a compost pile because it is slower,creates unpleasant odors, and produces little hea
3、t.Nutrients The decomposer organisms obtain many nutrients fromthe composting ingredients, but carbon (C) and nitrogen (N) areparticularly important. A well-balanced proportion of carbon andnitrogen usually ensures a good supply of all nutrients and allowscomposting to proceed rapidly. A balance of
4、carbon and nitrogencan be achieved by combining carbon-rich or “brown” materialswith nitrogen-rich or “green” materials (see “Recipes for Success”).Degradability The speed at which composting occurs is largelydetermined by the degradability of the materials, that is, how easilythey decompose. Microo
5、rganisms easily digest materials contain-ing a high proportion of sugars, starches, and proteins, such asFigure 2. Basics of the composting processHeatWater Carbon DioxideOrganicIngredientscontaining carbon,nitrogen, other nutrients,water, minerals,microorganisms, etc.Compostcontaining organicmatter
6、, nutrients,minerals, water,microorganinisms, etc.TheCompostingProcessAir (oxygen)6food scraps, manure, and green vegetation. Straw, plant stems,and, especially, woody materials take longer to decompose andmay even pass through the composting process with little change.You will notice that many nitr
7、ogen-rich materials (greens) tend todecompose quickly, while the carbon-rich materials (browns) areless degradable. The degradability of a material is enhanced byshredding and by ensuring that adequate amounts of nitrogen andwater are available.Moisture Microorganisms need moisture to carry out thei
8、r work. Ifthe materials are dry, the process slows down. On the other hand,too much water makes the compost pile soggy and dense, whichhinders aeration. Composting materials should be moist but notdripping wet.Surface area The decomposer organisms work on the surface ofparticles. Because smaller par
9、ticles offer more surface area,composting is generally faster when materials are chopped,shredded, or cut into pieces. However, a pile with only fine particlesis dense and therefore does not aerate well. Particles in the rangeof 1/4 to 2 inches usually compost well. As decompositionprogresses, parti
10、cles shrink in size and tend to compact. Turninghelps to loosen the compacted particles and improves aeration.Temperature Heat generated by the microorganisms duringcomposting raises the temperature of the composting materials.The temperatures in a compost pile often rise above 120F andsometimes exc
11、eed 160F. High temperatures (above 140F) havethe advantage of killing pathogens (microorganisms that causedisease) and weed seeds. Because backyard composting piles aresmall, they may only sustain elevated temperatures for one or twodays. Thats OK. Good compost can also be produced by moder-ate temp
12、eratures. Unless the material being composted is diseasedor contains many seeds, achieving high temperatures is not important.Time Depending on the ingredients and conditions in a pile, it cantake several weeks to over a year to produce compost. Compost istypically ready for use in three to six mont
13、hs, given regular turning,adequate moisture, and a good mixture of materials. With dailyturnings and highly degradable ingredients, the composting timecan be reduced to less than one month. Methods that involve littleor no turning usually require more than a year to produce compostthat is ready to u
14、se.7What to Compost,What Not to CompostWhile most natural organic materials will decompose in time, noteverything belongs in the backyard compost pile (see Table 1).Many readily available organic materials are good candidates forthe backyard compost pile. Garden vegetation, landscape trim-mings, and
15、 most plant-derived food scraps can generally becomposted without concern. In moderation, you can also addmanure from livestock and poultry.Avoid composting plant material that is diseased or that carries anabundance of seeds and insects. You should also avoidcomposting grass clippings that have bee
16、n treated with persistentherbicides (see “Managing Grass Clippings in the Compost Pile”).Certain invasive weeds, such as morning glory (bindweed) andquack grass, are best left out of the compost pile. Backyard com-post piles do not reliably produce enough heat to destroy plantpathogens, rhizomes, an
17、d seeds. For the same reason, cat anddog feces, which can carry pathogens, should not be added tocompost piles. Fatty and oily foods should be avoided becausethey are more likely to generate odors and attract animal pests,such as flies, dogs, and rodents.9Table 1. Materials that can be composted, an
18、d materials thatshould not be composted(Adapted from Composting to Reduce the Waste Stream)Can be compostedAquatic plantsBreadBranches, chippedBrush, chippedCoffee groundsCompost recycled from previous batchesCorn husks, stalks, and cobsCut flowersEggshellsEvergreen needlesFruitFruit peels and rinds
19、Garden trimmingsGrass clippingsLeavesManurecattle, horse, chicken, rabbit, etc.PaperSawdustSoil, garden and pottingStrawSodTea leaves and tea bagsVegetablesVegetable tops and trimmingsWeeds without seedsWood ashWood chips and shavings10Should not be compostedMaterials that produce odorsor attract pe
20、sts (oily foods)ButterBonesCheese and other dairy productsFish scrapsLardMayonnaiseMeat and poultryPeanut butterSalad dressingSour creamVegetable oilPossible sources of weeds and diseaseCat manureDog manureDiseased plantsPlants with spreading rhizomes and invasive roots,such as quack grass and bindweedWeeds that have gone to seedPossible sources of toxinsPlants or grass treated with persistent herbicidesTreated or painted wood, shavings, or sawdustWalnut leaves11
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