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f S `1 COMPOSTING AND MULCHING: A GUIDE TO MANAGING ORGANIC YARD WASTES Composting is a microbial process that cumerts pl.int mate- rials such as grass clippings and Icwr~~ to a u~ihlc ur};anic soil amendment or mulch. C;ardc~ner~ h,rvc u~c~d < onrl a rat for centuries to increase soil organic matter and scrppl} some of the essential nutrients for plant growth. Aful< hing refers to the practice of applying a substance such as compost or grass clippings to the soil surface with the• purtx,~e of modifying soil temperature and moisture as well as controlling w-eeds and soil erosion. With the ban on outdoor burning and with laws which soon will limit dumpingof (caves and grass c liphings into landfills, composting and mulching have become attractive alterna- tives for managing yard waste and recycling natural materi- als. Grass clippings and leaves can be hauled to city composting areas as one means of disposal. How-ever, many homeowners may find it more convenient and economical to compost these materials in their ow•n back} ands. In either case, the finished compost can he used as a mulch or as a soil amendment to improve most garden ~cril~. This bulletin should help you learn huw~ to build and nnint,~in a c onrpust pile as well as how to use the compost in the yard and gar- den. • Why Compost? J Composting is an efficient method of breaking down organic materials into an end product that is beneficial to the soil and growing plants. Adding undecomposed materials directly to the sot{ without first composting may initially have some un- desirable effects. For example, i(largc quantities of uncom- posted leaves are incorporated into the soil, microbes will compete with plant roots for soil nitrogen during Icaf decom- position.This competition for nitrogen can result in nitrogen deficiency and poor plant growth. Adding composted mate- rial reduces the competition for nitrogen. Another benefit of composted material is that it is much easier to handle and mix with soil than uncomposted material. furthermore, im- provement of soil ph}-steal properties, such as infiltration, .drainage, and water holding capacity, will usually be faster if composted materials are added. Requirements for Efficient Decomposition Decomposition of organic material in the compost pile is de- pendent onmaintaining microbial activity . Am factor which slows or halts microbial growth „ill also impede the com- postingprocess. Efficient decomposition w ill occur if the fol- (owingfactors are used to fullest advantaRe~. Aeration: Oxygen is rcquirecl fur mirn~h~~~ tc~ ctticic~ntl~ dc- compose the organic ~~•astcs. Soma dc~c rmrt,ucition kill oc- . cur in the absence of oxygen tanaerul~ic conditions); however, the process is slow and foul r-dor. may dc~ clop. Mixing the pile once or M-ice a month ~~ ill t~ro~ ide the neces- sary oxygen and significant)}~ hasten the composting pro- . Bess. A pile that is hot mixed may take three to four times longer before it can be used. A well mixed compost pile will also reach higher temperatures which will helpdestroy weed seeds and pathogens. Moisture: Adequate moisture is essential for microbial activ- ity. Adry compost will not decompose efficiently. tf rainfall is limited, it wil I be necessary to water the pile periodically to maintain a steady decomposition rate. Enough water should be added to completely moisten the pile, but overwatering should be avoided. Excess water can lead to anaerobic con- ditionswhich slow down the degradation process and cause foul odors. Water the pile so that it is damp, but does not re- mainsoggy. Particle size: The smaller the size of organic wastes, the faster the compost will be ready for use. Smaller particles have much more surface area that can be attacked by mi- crobes. Ashredder can be used before putting material in the pile, and is essential if brush or sticks are to be composted. A (uw curt methcxl of rcduc ing the size of fallen tree leaves is to mow the lawn Ix~furc raking. if the mower has an appropriate bag attachment, the shredded leaves can be collected di- rectly. In addition to speeding up the composting process, shredding will reduce the initial volume of the compostpile. fertilizer and lime: Microbial activity is affected by the car- bon tonitrogen ratio of the organic waste. Because microbes require a certain amount of nitrogen for their own metabolism and growth, a shortage of nitrogen will slow down the composting process considerably. Material high in carbon relative to nitrogen such as straw or sawdust will de- compose very slow~l} unless nitrogen fertilizer is added. Tree leaves are higher in nitrogen than straw or sawdust but de- comhosition of leaves would still benefit from an addition of nitrogen fertilizer. Grass clippings are generally high in nitro- gen and when mixed properly with leaves wiN enhance de- composition. Manure or blood meat can be used as organic sources of nitrogen. Otherwise, a fertilizer with a high nitro- gen content should be used. Other nutrients such as phos- phorus and potassium are usually present in adequate amounts for decomposition. During tl~e initial stages of decomposition organic acids are produced and the pH dropc. In the past, small amounts of lime have been suggested for maintaining and enhancing microbial activity at this time. However, high rates of lime will convert ammonium-nitrogen to ammonia gas which will lead to the loss of nitrogen from the pile. Research has shown that althou>~h lime additions may hasten decomposi- tion, tl-e loss of nitrogen from the pile often offsets the bene- fits of lime 11 ). In general, lime is not necessary for degradation of must yard w antes. The pH of finished compost is usuall} slightly alkaline ~rithout the addition of time. In many areas, the water used to moisten the compost pile is sufticientl} alkaline to increase the pH of the compost. If large quantites of pine needles or fruit wastes are composted, some additional lime ma} be necessary. ,