Agaricus Mushroom Growing

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  • forAgaricus MushroomGrowing

    Basic Procedures

    College of Agricultural SciencesAgricultural Research and Cooperative Extension

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    Hippocrates first mentioned mush-rooms when he wrote about theirmedicinal value in 400 B.C. The firstmention of mushroom cultivation,distinct from a chance appearance inthe field, was in l652. Unfortunately,they were described as excellent formaking into compresses for ripeningboils but not as good to eat. In l707,a French botanist wrote about mush-rooms as originating from a horse.He went on further to note, Sporesupon germination developed into afluff, this fluff, planted into horsemanure and covered with soil, wouldgrow mushrooms. The first record ofyear-round commercial productionwas in l780 when a French gardenerbegan to cultivate mushrooms in theunderground quarries near Paris. Afterthe Civil War, gardeners introducedmushroom growing to North Americaby using dark areas underneathgreenhouse benches to grow mush-rooms.

    In spite of some articles that saymushrooms can be grown in any darkhole or building, successful commer-cial mushroom growing requiresspecial houses equipped with ventila-tion systems. While mushrooms areusually grown in the absence of light,darkness is not a requirement. Mush-rooms have been grown in unusedcoal and limestone mines, old brewer-ies, basements of apartment houses,natural and man-made caves, rhubarbsheds, and many other unusualstructures. Mushrooms were report-edly grown in an old dairy barn,which was so damp that cows living init had died of pneumonia. In l894, thefirst structure specifically designed togrow mushrooms was built in ChesterCounty, Pennsylvania, which isusually referred to as the mushroomcapital of the world.

    Growing mushrooms is a waste-recycling activity. Mushroom farmsbenefit the environment by usingmany tons of mulch hay, straw-bedded horse manure, and poultrymanure. These products are consid-ered agricultural waste products andwould not have a home if it were notfor mushroom production. Mush-room production is both an art and ascience with many complex anddistinct stages.

    This fact sheet will outline the overallmushroom production cycle and givea brief description of each of theproduction stages. Phase I and PhaseII composting, spawning, spawncolonization (Phase III), casing, caserun, pinning, and harvesting are theprimary stages of the mushroomproduction cycle. The specific criteria(temperature set points, carbondioxide concentrations, and so forth)involved in each stage will changedepending on different mushroomcrops and different mushroomgrowers, but the basic concepts andmethods of mushroom productionremain constant. Although a writtendescription of mushroom growingmay seem simple, the process ofpreparing a composted substrate andits pasteurization is quite complex.Potential growers are encouraged togain cultural experience on an existingfarm before embarking on a privateenterprise.

    A few mushroom farms are located inlimestone caves where the rock acts asboth a heating and cooling surface,depending on the time of the year.Mushroom growing is not necessarilyappropriate for caves or abandonedcoal mines since they have too manyintrinsic problems to be consideredreliable sites for mushroom farms. Thesame is true for other dark, humidspaces of any sort. Limestone cavesrequire extensive renovation and

    improvement before they are suitablefor mushroom growing. Compostingtakes place above ground on a wharf,and only growing and harvestingoccur in the cave.

    A Review of MushroomGrowing

    The mushroom is a fungus and isquite finicky about its food source.Mushrooms lack the ability to useenergy from the sun. They are notgreen plants because they do not havechlorophyll. Mushrooms extract theircarbohydrates and proteins from arich medium of decaying, organic-matter vegetation. This rich organicmatter must be prepared into nutri-ent-rich substrate composts that themushroom can consume. Whencorrectly made, this food may becomeavailable exclusively to the mushroomand would not support the growth ofmuch else. At a certain stage in thedecomposition, the mushroom growerstops the process and plants themushroom so it becomes the domi-nant organism in that environment.

    The sequence used to produce thisspecific substrate for the mushroom iscalled composting or compost sub-strate preparation and is divided intotwo stages, Phase I and Phase II. Eachstage has distinct goals or objectives. Itis the growers responsibility toprovide the necessary ingredients andenvironmental conditions for thechemical and biological processesrequired to complete these goals. Themanagement of starting ingredientsand the proper conditions forcomposting make growing mush-rooms so demanding.

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    Making a CompostedSubstrate

    Many agricultural by-products areused to make mushroom substrate.Straw-bedded horse manure and hayor wheat straw are the common bulkingredients. Synthetic composts arethose in which the prime ingredient isnot straw-bedded horse manure. Ifbulk ingredients are high in nitrogen,other high-carbohydrate bulk ingredi-entssuch as corncobs, cottonseedhulls, or cocoa bean hullsare addedto the mix. All compost formulasrequire the addition of nitrogensupplements and gypsum.

    Additional nitrogen-rich supplementsare added to composts to increase thenitrogen content to 1.51.7 percentfor horse manure or 1.71.9 percentfor synthetic; both are computed on adry weight basis. Poultry manure isprobably the most common andeconomical source of nitrogen. Avariety of meals or seeds, such ascottonseed meal, soybean meal, orbrewers grain may also be used.Inorganic or nonprotein nitrogensources such as ammonia nitrate andurea are also used, but only in smallamounts when high-carbohydratebulk ingredients are used. Gypsum isadded to minimize greasiness and tobuffer the pH of the compost.Gypsum increases the flocculation ofcolloids in the compost, whichprevents the straws from stickingtogether and inhibiting air penetra-tion. Air, which supplies oxygen to themicrobes and chemical reactions, isessential to the composting process.Gypsum may be added early in thecomposting process, at 70100 lbs perton of dry ingredients.

    A concrete slab, referred to as a wharf,is required for composting (Figure 1).In addition, a compost turner toaerate and water the ingredients and atractor-loader to move the ingredientsto the turner are needed. Water usedduring a substrate preparation opera-tion can be recycled back into theprocess. It is, in a sense, a closedsystem. Water runoff into the environ-ment is nonexistent on a properlymanaged substrate preparation wharf.Water collected in concrete pits or asealed lagoon is aerated and recycledto soak bulk ingredients before thecomposting process begins.

    Conventional Phase I compostingbegins by mixing and wetting theingredients as they are stacked. Mostfarms have a preconditioning phase inwhich bulk ingredients and somesupplements are watered and stackedin a large pile for several days tosoften, making them more receptiveto water. This preconditioning timemay range from 3 to 15 days. Thepiles are turned daily or every otherday. After this pre-wet stage, thecompost is formed into a rectangularpile with tight sides and a loose center.A compost turner is typically used toform this pile. Water is sprayed ontothe horse manure or synthetic com-post as these materials move throughthe turner. Nitrogen supplements andgypsum can be spread over the top ofthe bulk ingredients and are thor-oughly mixed by the turner.

    Figure 1. Traditional compost wharf, showing pre-wet pile on the right and thericks or windrows on the left.

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    Figure 2 is a close-up of a machineeating its way through a compostpile. Once the pile is wetted andformed, aerobic fermentation(composting) commences as microbialgrowth and reproduction naturallyoccur in the bulk ingredients. Heat,ammonia, and carbon dioxide (CO


    are released as by-products during thisprocess. Compost activators, otherthan those mentioned, are not needed.

    As temperatures increase above 155F(70C), microorganisms cease growingand a chemical reaction begins.Concentrating and preserving com-plex carbohydrates is one goal ofPhase I. The quantity and the qualityof nitrogen in the system are changedto a type of nitrogen that Phase IImicroorganisms and, eventually, themushroom will use as food.

    Adequate moisture, oxygen, nitrogen,and carbohydrates must be presentthroughout the process; otherwise, theprocess will stop. This is why waterand supplements are added periodi-cally and the compost pile is aerated asit moves through the turner. Oxygen-ation is achieved in conventionaloutdoor ricks by natural convection.The high pile temperatures drawambient air through the sides of thestack, and as the air is heated, it risesupward through the stacka processcommonly referred to as the chimneyeffect (Figure 3). The sides of the pileshould be firm and dense, yet thecenter must remain loose throughoutPhase I composting. The exclusion ofair results in an airless (anaerobic)environment. As the straw or haysoftens during composting, thematerials become less rigid and morecompact while substrate densityincreases. Thus, less air reaches thebottom and center of the pile. A lackof oxygen may occur after the largequantities of water are added to thedry bulk ingredients and before

    sufficient heat is generated to start thedraw of air into the pile. Underanaerobic conditions, organic acidsand other deleterious chemicalcompounds are formed. Therefore,

    preparing substrate under aerobicconditions, where less offensive odorsare produced, is better for mushroomgrowers.

    Figure 2. Self-propelled compost turner moving through a compost rick or pile.

    Figure 3. Cross section of a compost pile showing the different temperaturezones and air movement (blue arro