Intro Growing

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INTRODUCTION TOMUSHROOM GROWING

Although we enjoy mushroomstoday as an every-day vegetable,

this wasnt always the case.Mushrooms date back to ancientEgyptian times, when they wereconsidered a rare luxury. In fact, theearliest documented reference tothe use of mushrooms as a food isattributed to one of the Pharaohswho decreed them to be too fine afood to be eaten by the commonpeople. Records from Greece in

the period c300 BC refer to mush-room feasts and note that even thenthe Greeks were exporting them toneighbouring lands. The Romanswho enjoyed mushrooms and JuliusCaesar passed laws about who waspermitted to enjoy the unique flavourof mushrooms.

For centuries, the edible mushroomdefied cultivation. It wasnt until the

late 15th century that cultivation ofmushrooms began in disused

quarry tunnels in France.

Mushrooms are a naturalproduct with many nutritionaladvantages. They arecholesterol free and containvirtually no fat or sodium, allof which dietitians say need

to be reduced in Australiandiets. Mushrooms supply

dietary fibre and are a good sourceof several important B group vitamins,

especially niacin and riboflavin.

The sophistication of todaysmushroom farms is in markedcontrast to the first commercialattempts to grow this crop inAustralia in 1933. At that time,mushrooms were grown in the openfield in raised beds covered in strawand hessian bags, although some

were also grown in cellars or otherfarm sheds. The first growinghouses of any size were disusedrailway tunnels (including the thenincomplete Circular Quay - StJames line).

Mushroom growers commencedoutdoor cultivation in the Hills andHawkesbury districts outsideSydney in the mid-1930s. There

were several reasons for thislocation, including:

it was close to a migrant camp atSchofields where many fromEuropean backgrounds who hadgrown mushrooms in their home-lands first settled in Australia;

raw materials for substratepreparation (eg straw from the

expanding racing industry) couldbe obtained locally;

For further information contact AMGALocked Bag 3, Windsor NSW

Ph: 61 2 4577 6877, Fax: 61 2 4577 5830Email: [email protected]


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access to a large and willing labour force; proximity to the burgeoning markets of

Sydney, which was important for a perishablecrop in the days before refrigeration.

Two major issues have affected the industry sinceits inception:

1. Changing Tariff Policy on Imports.The Australian governments changing policyon tariffs has had a significant impact on themushroom industry. In the mid-1970s theAustralian industry was heavily dependent onsales to canneries. However, with the lowering oftariffs, the market was threatened by cannedproducts imported from low cost labour countries,mainly in the Asian area.

As the domestic canned market was eroded,

growers were forced to concentrate on promotionof fresh mushrooms to develop new marketopportunities. This has been a most successfulventure; in 1974 less than 25% of local productwent to the fresh market; by 1991, this hadincreased to more than 90%.

2. Changing Growing Methods

In common with much of Australian agriculture in the1930s, production methods were still substantially

the same as they had beenin 19th century Europe.

Mushrooms wereoutdoors in

raised bedscovered withstraw. InA u s t r a l i a nclimates, thismeant they

were grownmainly as aseasonal crop

in the coolermonths, as

mushrooms require low temperature ranges tocrop properly. Increasingly sophisticatedtechnologies and demands for better quality andsupply from consumers have seen a dramaticturn around in production methods. Modernmushroom farming emerged on a world-widebasis in the 1960s.

Scientific breakthroughs in the manufacture ofsubstrate enabled growers to increase productionand quality, and extend the growing season.Today, mushrooms are grown commercially inenclosed atmosphere controlled environments,production is therefore largely independent of theenvironment. Mushrooms are grown in a seriesof identical rooms, with the number of roomsdetermined by the production cycle. Crops ofhigh quality mushrooms are now producedall year round and mushrooms are a regular

inclusion on Australian menus.

PRODUCTION TODAY

Production StatisticsMushrooms are the third most valuable vegetablecrop in Australia - after potatoes and tomatoes. Arecent government study of new horticulturalindustries identified the mushroom industry asone of the three most successful new industriesin Australia.

Most of the mushrooms produced in Australiaare common white mushrooms (agaricusbisporus). There is a growing demand forspecialty mushrooms (eg shiitake, pleurotus,straw etc) and a niche market will continue todevelop for these products over the next fewyears. Virtually all local production is consumedin the domestic market. Around 90% of domesticproduction is consumed as fresh mushrooms with

only small quantities going to processing. Thisratio has changed dramatically over the last 20years: from 75%:25% canned fresh in themid1970s; to 8%:92% at present. The marketshare of imported mushrooms has also


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decreased significantly over recent years to lessthan 13% of domestic consumption. Importedmushrooms are used mainly in the processingindustries.

The industry has been growing at a much fasterrate than the national economy as a whole; andcertainly faster than most other agricultural

industries. Domestic mushroom production hasexpanded at an average annual rate of about10% per annum since 1974. In 1995/96, the rateof increase was in excess of 16%. The industryis forecasting further increases in domesticproduction, with an estimated growth rate of morethan 10% during the next two years. Thisincrease will largely result from improvedproductivity and efficiency on existing farms.

The industry is a significant employer. Industry

figures show that in excess of 2,000 people areemployed directly by the mushroom industry.

The mushroom industry is very labour intensive,every mushroom being picked by hand. As theindustry has grown, so too have the requirementsfor a reliable local labour market.

Despite the countrys poor economicperformance, the price paid by consumers

for mushrooms hasremained relatively

constant over thelast few years. It

has only beenpossible forgrowers tomaintain thislevel of returnby becoming

more efficientand producingbetter quality

m u s h r o o m smore consistently.

Production Methods

Organic wastes from other primary industriesare used in the production of substrate in whichmushrooms are grown. Raw materials used inmushroom substrate production which areby-products of other industries include wheatstraw, poultry manure, stable waste. Thesematerials, if not recycled, could pose potential

environmental threats. These ingredients areblended together and organically substrated toproduce a nutrient-rich medium in which togrow mushrooms. Once the crop has beenharvested, the pre-loved substrate provides anorganic and nutritionally balanced product, idealfor addition to high quality potting mixes or useas a garden mulch.

Mushroom growing is one of the fastest growingand most technologically sophisticated

horticultural industries in the world. However,the raw materials for growing mushrooms owelittle to scientific technology. Science has yet tocome up with a viable substitute quite as goodas old-fashioned substrate.

The mushroom industry is the ultimate recycler.Mushroom substrate is made from wheat straw;stable bedding; poultry litter; and other organicmaterials. These by-products of other primary

industries are used to produce a selectivenutrient-rich medium for production of a highquality food stuff. After these materials are mixed,the substrate is then fermented and pasteurised.

Spore (the seed of the mushroom) is used toproduce grain spawn under sterile conditions.The mushroom spawn is then added to thesubstrate. Mushrooms are grown in sophisticatedrooms in which the environment is precision

controlled to provide ideal growing conditions.Constant checks ensure that temperature, aircomposition and humidity are kept at the rightlevels while the spawn grows through thesubstrate. A surface of peat moss is then added


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to the substrate to provide a good bed on whichthe mushrooms will multiply. At every stage ofthe process, the environment is carefullymonitored and hygiene strictly controlled.

The growing process is unusual becausemushrooms do not have leaves or a root systemlike other crops; nor do they need sunshine or

chlorophyll. Growers have made big investmentsin climate-controlled growing environmentsspecifically designed for mushrooms to ensurethat quality fresh mushrooms are available forconsumers every day of the year. The firstmushrooms will appear in about twelve days andbe ready for harvest in about three weeks.

Harvesting is done by hand by teams of trainedpickers. Each tray or bag of substrate producesthree commercially harvestable crops (called

flushes) over a period of about six weeks. Oncethe crop has been harvested, the pre-lovedsubstrate provides an organic and nutritionallybalanced product ideal for addition to high qualitypotting mixes or use as a garden mulch. Thus,nothing is wasted.

INDUSTRY STRUCTURE

The industry is highly capital intensive andtechnically oriented, with most production coming

from a relatively smallnumber of large

producers. Thereare approximately

80 farms locat-ed throughoutA u s t r a l i a .This numberhas beendecreasing

over recentyears, ascosts of updat-

ing to moremodern technology

have driven less efficient producers out ofthe market. The only main concentration ofoperations is in the Hawkesbury district ofSydney, with about half the nations farms and40% of production located in this area.

Because climatic or soil conditions are irrelevantto the production of mushrooms, location is not a

real issue. Farms need to be near to markets ifcosts are to be controlled, and must have accessto good transport and supplies of labour.

Farms which make their own substrate must alsoconsider the source of raw materials, as these arebulky and difficult to transport over longdistances. There are, however, some specialistsubstrate makers who will supply substrate tofarms which do not wish to undertake thisprocess themselves.

The Australian Mushroom Growers Association(AMGA) represents 95% of Australian mushroomfarms. The industry association is very strong andpro-active. There is a very high level of industryparticipation and co-operation, with membersactive at both state and national level, as well ason committees across a wide range of areas.TheAssociation has a secretariat in Windsor (Sydney)to service its busy program of activities.

The mushroom industry is one of only twohorticultural industries in Australia which collectsa voluntary levy to fund promotion and research.The levy is collected by AMGA on all spawn usedin Australia and raises approximately $1.5 millionper annum. These levy funds are then used tofund a range of activities including: research anddevelopment; marketing and promotion; lobbyingand representation; education and training.

The Pareto principle applies in mushroomfarming - 80% of the production comes from 20%of the farms. Mushroom farms fall into four maincategories:


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1. Production of < 250 tonnes per annumThese are family farms, with family membersdoing all the work including picking. They areoften operating at the lowest level of technologyand capital investment. Turnover on these farmswould be less than $1 million per annum.

2. Production of 250 - 750 tonnes per annum

These are family farms, but with casual labourhired to assist with picking and other tasks.Capital investment is usually higher with newerfacilities and technologies. Turnover on thesefarms would be between $1 - $5 million perannum.

3. Production of 751 - 2,500 tonnes per annumThese are usually family farms but with higherstaffing ratios. The family usually maintainsmanagement control, but has employees in most

other roles.

Technology is sophisticated and specialisedequipment and personnel, and the level of capitalinvestment is substantial. Turnover on these farmswould be between $5 - $15 million per annum.

4. Production of >2,500 tonnes per annum.There are only a few farms in this category, witha mix of family and corporate ownership.

The level of technologicalsophistication varies,

as it is usual toupdate farms

such as theseover time.High numbersof casualstaff areemployed for

picking, andspecialists areemployed for

other tasksincluding manage-

ment, sales, substrate making and growing.Turnover for these farms would exceed $15million per annum.

PRODUCTION

Growing systemThree systems are used for mushroom growing:

Tray growing is used mainly by mediumand large growers. This is the major methodused for the growing of mushroomsin Australia. Trays are made of wood,usually lm x 2m x 0.3 m in size fastenedusing stainless steel fittings.

Bag growing is becoming increasinglypopular with small to medium growers andnew entrants into the mushroom industry.This system requires a smaller capitaloutlay than the tray system. Bag growing

offers advantages in pest and diseasecontrol by allowing fast and easy removalof infected bags. However, theseadvantages are offset because bag growingrequires a larger labour input per kilo thaneither of the other two systems.

Shelf growing is the growing system of choicein Holland, but is used by only a few growersin Australia. It offers large savings in labourcosts but this is offset by very large capital

setup costs.

Each of these growing systems is economicallyviable in some circumstances and all arerepresented in the mushroom industry in Australia.

Of paramount importance is the level of expertise inrequired in both management and growing methodsin mushroom growing. If skills in either area are lack-ing, production can vary greatly between crops

regardless of the growing system used.

TECHNOLOGY AND TERMINOLOGY

Mushroom growing is highly technical and the useof a number of technical terms is unavoidable.


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Mushrooms are fungi. Unlike green plants,theycannot convert sunlight into energy(photosynthesis) because they lack chlorophyll.Like other higher organisms including ourselves,fungi need to have food made for them. Formushrooms, this means complex carbohydrates,microbial proteins, etc. Unfortunately, there is nopure source of these raw materials readily

available in nature. Rather, in any organic matterthere exists a great variety of simple andcomplex compounds.

Cultivated mushrooms cannot compete with lowerclass organisms, eg bacteria and some fungi in theclass, fungi imperfecti. This is due to a variety offood being available in the raw ingredients and thecompetitive advantage which simpler organismshave in digesting these ingredients.

It is therefore necessary to find a way to providethe mushroom with a high quality growthmedium in which the mushroom can have thecompetitive advantage.

MUSHROOM GROWING

Modern mushroom growing consists of threesequential phases each of which is dependent onthe previous one.Phase I: Production of substrate (composting).

This is carried out in aspecific area of the

farm called thecompost yard.

Phase II:Peakheat orpasteurising.Phase III:Production ofmushrooms.

Phases II and

III are carried

out in sheds or

growing rooms.

PHASE I: PRODUCTION OF SUBSTRATE

Phase I involves the preparation and mixing of rawingredients to produce a substrate on whichmushrooms can be grown. This is commonlycalled phase I compost. This process usuallytakes place out of doors and it takes between14-28 days to produce a compost ready forfilling. Ingredients used in the production of

mushroom compost can include: wheaten straw;horse manure and/or poultry manure;gypsum andwater. Large quantities or water are also used.

Production of compost requires: large areas of concrete surface for stockpiling

raw materials, preparation of compost heapsand transferral of materials on site.

access to large quantities of water andconstruction of reticulation and water storagesystems.

mechanical compost turning equipment asturning compost by hand is very slow andlabour intensive and therefore very costly. It isonly possible on a small scale and does notresult in a compost sufficiently consistent toproduce good yields and commercial qualitymushrooms.

machinery for mixing and moving rawmaterials and compost in various stages of theprocess would include front end loaders,

forklifts and a compost turning machine. in most cases, local government approval

is required as odoursresulting from thecomposting process may create a nuisance.

Production of compost is a complex process. Itincreases the set up costs of a farm and also theeffort required by the grower.

Some small farms (less than 3 tonnes per week) opt

to purchase bags of compost ready spawned toovercome this problem. These are referred to assatellite growers. In areas where there areconcentrations of growers it is sometimes possible topurchase compost from specialised compost makers.


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PHASE II: PEAK HEATING OR

PASTEURISATION

After the compost is ready, it is filled into thepeakheat room. Compost can be filled intoconventional trays or pasteurised in bulk inpurpose-built tunnels. Phase II has a duration of7-10 days. Filtration (to 2 n), of air is veryimportant at this stage to prevent any fungal and

insect pathogens from infecting the compost.

It is possible to grow mushrooms without peakheating (pasteurising) the compost by extendingthe Phase I period. However it is noteconomically feasible because of the variabilityintroduced. This results in lower yields andpoorer quality mushrooms.

Phase II comprises a number of separate stages,during which temperatures are varied according

to a precise schedule. The different stages are:

LevellingAfter filling the compost, temperatures are levelled.

HeatupOnce levelled the compost temperatures areallowed to climb to 60C.

Kill

When the temperature reaches 60 C it ismaintained for severalhours to allow the

pasteurisation orkill to take place

and removep a t h o g e nloads eg. fliesand competi-tor fungi.

C o o l d o w nfrom Kill

Following the killthe temperature of

the compost is brought down to approximately48-52C over the desired time period.

ConditioningThe compost temperature is maintained atbetween 48-52 C to allow conversion ofgaseous ammonia into microbial biomass to beused as food by the mushroom.

CooldownWhen the ammonia (NH3) is below 10 ppm,temperature of the compost is brought down tobelow 25 C. The compost is now ready tobe inoculated with the mushroom fungus. Theindustry term at this stage is ready for spawning.

PHASE III: PRODUCTION OF MUSHROOMS

Phase represents the actual growth of the

mushroom fungus. It can be broken into thefollowing phases:

SpawningOnce phase II, is complete the compost isspawned. Spawn is mixed with compost and thenfilled into bags, trays or shelves.

Spawn runningAfter spawning, the crop is moved to either a

specialist spawn-running room or directly to thegrowing room. The temperature of the compost isallowed to climb to 2S C; the carbon dioxide isallowed to build up.

During the next 10-14 days, the humidity shouldbe maintained between 95-100% to preventdrying out of the top of the beds. This may beachieved by watering the walls and floor or bycovering the beds with plastic or paper. If paper isused, it should be kept wet.

Ideally, the room should be humidified. When thesurface of the compost is covered with a whitishgrowth, the beds are ready for casing.


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The growing area which can be prepared from 1tonne of compost will vary with the quality ofcompost and the depth of fill. Approximately10-12 tonnes of raw compost at 72% moisture atthe end of Phase I is required per 100 m2 ofgrowing area for a 15 cm depth of fill.

Around 20-25% of the weight of the raw compost

is usually lost during peak heating and another7-10% during spawn run (due to loss of moistureand dry matter).

SupplementationAt this stage, some growers add a proteinsupplement to the compost to enhance yield.This isoptional.Various products are available commerciallyfor this purpose. Care should be taken as atemperature surge can result from supplementation.

CasingOnce the spawn has grown fully through thecompost, a casing layer is added.A peat/limestonemix is the most widely used casing material. Somegrowers use soil peat moss combinations butthis involves additional handling and steampasteurisation. Casing mix usually comprises, onelarge bale of peat moss mixed with 1 bag of superfineagricultural lime and 90-100 litres of water and willcover 8-10 m2 of bed area in a layer 5 cm thick.

The basic functions of thecasing layer are to:

protect thecompost fromdrying out; provide humidm ic roc l ima tefor fruit bodyformation and

development; provide amoisture reser-

voir for maturingmushrooms.

Casing material should not be so wet atapplication that water runs into the compost. Manygrowers use chemicals (fungicides and/orinsecticides and/or nematicides) in their casing asa routine measure to try and prevent severe pestand disease outbreaks. If chemicals are used theyare best incorporated at the time of mixing to enablegood distribution in the casing layer but should not

be considered a substitute for good hygiene.

At this stage, fully grown compost can be addedto the casing material.

This is known as CAC-ing (compost added atcasing). The added compost acts as inoculum inthe casing layer allowing a more even colonisationof the casing layer by the mushroom mycelium andresults in more even cropping.

However, those contemplating CAC-ing shouldfollow extreme hygiene practices and seek advicefrom an experienced grower or consultant asfailure to manage and select the correct CACmaterial can result in total crop loss.

Case runThe crop is then moved to a specialist caserun room or directly to the cropping room. Themushroom fungus is allowed to colonise the casing

layer and water is added to the casing as required.

Fresh airWhen the appropriate casing growth is seenaccording to the strain, fresh air is introduced intothe room and the temperature is reduced toinduce mushroom formation.

PinningPins are the first emerging primordial fruit bodies

of the mushroom fungus. As the mushroommycelium starts to form the mushrooms, theclimate and pattern of environment managementis adjusted to ensure the right number of pinsform and begin to grow out.


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CroppingPins now mature into mushrooms. Mushroomcrops grow in what are known as flushes. Thefirst flush is harvested 17-21 days after casing.Most growers harvest 3-4 flushes per crop.During cropping temperatures are held between16-19C. Water is applied as required.

Harvesting the CropMushrooms are usually harvested in a 7-10 daycycle. However this may vary depending on anumber of factors including: temperature; humidity;strain; and the stage when they are picked.

Mushrooms are harvested by hand, so productionis very labour intensive. Picking costs compriseapproximately 60% of labour costs or 40% of totalcosts on a mushroom farm.

The performance of pickers will vary accordingto the experience and agility of the picker; freespace available between the trays, beds or bags;lighting; and the size and distribution of mushroomsstanding on the bed.Mushrooms are removed frombeds with a twisting motion. The stalk is thentrimmed. The mushrooms are usually gradedstraight into the boxes in which they will be sold.

Picking is a very skilled job. Pickers must be

careful not to damage the mushrooms.They must also be able

to select mushroomsfrom the bed when

they are readyto be picked.An averagepicking rate,for hybrids( i n c l u d i n g

grading), is12-15 kg/hourof good quality

b u t t o n / c u pmushrooms.

Mushrooms have the ability to double their size in24 hours. They can easily grow into an inferior,lower value product if not picked at the correct time.

Grading, Packing and DistributionFresh mushrooms are sold in three grades:buttons; cups and flats. Each grade refers toa stage of growth.

Buttons: these are small unopenedmushrooms which usually attract the highestreturns in the market place.

Cups: these are buttons which have beenallowed to grow until the cap has begun toopen so that some of the gills can be seen.

Flats: these are cups which have expanded sothat all the gills are visible.

Factory: these are mushrooms of all stagesof growth which are not up to fresh

market standard.

Within these grades, further grading is desirable.These sub grades are usually based on size,ie. large, medium and small.

Mushrooms are picked and packed with thestems upwards directly into the box or crate fordistribution. This minimises the handling of theeasily bruised mushroom fruit bodies.

Signs of deterioration of mushrooms include:brownish discolouration of surfaces; opening ofveils; elongation of stalks; and a general softeningof the surfaces due to loss of moisture.

Deterioration of the mushrooms will be minimisedif they are cooled immediately to between 2to 4C and kept cool throughout the entire distributionchain. Mushrooms are very perishable and their

appearance deteriorates each day, so theyshould not be stored for any length of time.

Most mushrooms are sold through wholesalemarkets as the demands of small private


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customers can be unpredictable and timeconsuming. One of the problems faced by asmall commercial mushroom farm away frommajor mushroom supply centres is to achieve acontinuity of supply.

Crop terminationAfter the final flush the crop is terminated by the

injection of wet steam into the growing room andthe raising of the temperature to 70C for 12 hours.This is referred to as cook out.Once cool again thecompost is moved off site and the room cleanedready for the next crop, the cycle starting again.

SEASONALITY

Mushrooms are unique amongst othervegetable crops in that they are grown in atotally artificially controlled atmosphere.Cropping is not dependent on the climate.

Mushrooms are not seasonal and are availableall months of the year. Of course, small growerswithout sophisticated climate control systemscan not grow over the hotter summer months.

SPAWN

Spawn is the inoculum used to grow mushrooms.Spawn is sterilised cereal grain colonised by thedesired mushroom strain. The grain provides thefood base for the fungus to grow from once the

spawn is distributedthroughout the

compost at the timeof spawning.

Several strainsof Agaricusmushroom arecommerciallya v a i l a b l e .

These include:white; off white;and hybrid types.

Within each ofthese groups, there

are a number of strains.These may differ in charac-teristics including: yield potential; ease of pinning;suitability of compost types; scaliness of the cap;average mushroom size and cropping pattern.Eachspawn manufacturer offers a variety of strains andwill provide advice on how they should be grown.

As in other parts of the world, hybrid strains are most

commonly grown in Australia.These strains are moredemanding in their requirement for the correctcompost, environmental conditions and watering.More losses and second quality mushrooms can beexpected if ideal conditions are not provided.Howeverthey do offer the possibility of producing good yieldsand good quality over a shorter cropping period.

Once purchased, mushroom spawn should bemixed with the compost as soon as possible.Spawn has a limited life. It can be stored at low

temperatures (2C) for several weeks; or at15-20C for a few days. Spawn should always bestored in a separate coolroom away frommushrooms or other likely contamination sources.

Care should be taken, especially during transit,as spawn performance can be affected by rapidchanges in temperature and temperatures thatare too high (over 30C).

Three to five kilograms of spawn should be usedper tonne of compost. When larger quantitiesof spawn are used, a considerable increase intemperature will occur in the beds generally 6-7days after spawning. If insufficient spawn is used,the extra time taken for the mycelium to colonisethe compost may enable pests and diseases toestablish and compete directly with the mushroommycelium. This will result in reduced yields.

YIELDSYields are generally stated in terms of kilogramsof mushrooms produced per square metre ofcompost. This refers to tray and shelf systems; inbag systems growers talk in terms of yield per bag.


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Whilst crop management is the most importantfactor determining yield, many other factors arealso influential. These include: the depth of fill;length of cropping; grade of mushrooms picked;quantity of compost per m2 (and whether it wascalculated at the time of filling, spawning or cas-ing); compost quality; productive capacity of thespawn, composition and moisture content of the

casing soil; climatic conditions in the growingroom; and the presence or absence of pests andor diseases.

The average yield for mushrooms in Australia isapproximately 22 kg per square mere of growingsurface area from 95 - 100 kg of compost (wetweight at spawning) for trays and shelves. Forbags, the average yield is 5.5 - 6 kgs per bag fromabout 20 kg of compost (wet weight at spawning).

Higher yields are of course possible but newgrowers with limited knowledge would not expectto achieve good yields in the initial stages.

The most economical period for picking isdetermined mainly by the total yield as wellas the growing system used on the farm. Theusual cropping period extends over 6 - 7 weeksand four flushes. However, around 80% of thetotal crop will usually be picked during the first 4

weeks (3 flushes).

Picking over longerperiods often creates

more problemsthan it is worth.Increased pestand diseaseproblems areusually experi-

enced andlabour costs areoften higher as

fewer mushroomsgrow on the beds.

Spent mushroom compost is a good soilconditioner. Many growers sell their spentcompost to landscape suppliers etc for onsellingto gardeners. This can be a useful addition tofarm income, but must be worked at if it is to be areliable earner. Returns for spent mushroomcompost will vary, depending on availability, localdemand, loading facilities and many other factors.

The availability of other organic mulch andcompost products has eroded the market which waspreviously solely filled by mushroomcompost. Sewage sludge and similar products arenow competing with compost, particularly in thebroad scale use areas, eg main roads departments;commercial landscape applications and so on.

There have been many instances of boguscomposts being passed off as mushroom

compost. This obviously creates problems forgrowers trying to sell their compost. However, theoutcomes are worse for consumers who buy theimitation stuff. When the results in their gardensare poor, they blame it on real compost and willnot buy more in the future. AMGA is working withStandards Australia to develop a standard formarketing product as spent mushroom compost.

STRUCTURES

Mushroom growing shedsMushrooms are grown commercially in purposebuilt rooms. Existing farm buildings such as fruitpacking sheds and poultry sheds can sometimesbe used but they will require major modifications.Even after modifications, there can still belimitations because of pest and diseaseproblems and their original construction.

Insulation

Insulation is required to prevent fluctuations intemperature and energy losses from heating andcooling. A common construction material used ispolystyrene or polyurethane sandwich panelssimilar to those used to construct coolrooms.


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Humidity and heat controlsControls are required to enable temperatureand humidity conditions within the shed tobe evenly maintained regardless of the prevailingweather conditions.

VentilationMushrooms need a supply of fresh air to ensure

growth is not inhibited by a build up of carbon dioxide.

AirfilteringAir filtering is required to help keep out air-bornespores and insects. Filtering to is highly recom-mended (2 ~m).

Cement floorsFloors must be of concrete with adequatedrainage to enable better hygiene management.

ROOM ENVIRONMENT AT DIFFERENTSTAGES OF CROPPING.

Peak heat (Phase II, pasteurization)During this process, the compost and air temper-atures should be maintained between 50C and60C for 7-10 days and humidity should be 90-100%. The air in the growing room should berenewed 25-30 times per hour (or 150-300 pertonne per hour) without allowing the surface ofthe compost to become too dry.

Spawn RunDuring this

period, roomtemperaturesof 25C for10-11 daysare preferred,with a highh u m i d i t y

(95-100%)to preventdrying out of

compost. Freshair is not required,

as a build up in carbon dioxide encourages thevegetative growth of the mushroom mycelium.

The temperature in the compost increases due tothe metabolic heat produced by the growingmycelium throughout spawn run. Sometimes therooms may require cooling to maintain thedesired compost temperatures.

PickingAn air temperature of 15-18C is required to keepthe temperature of the mushroom beds at16-20C. In summer, air temperatures this lowcannot be reached without a cooling system.

During picking, air in the room needs to berenewed several times per hour. It also needs tocirculate evenly throughout the room in order toremove any carbon dioxide and undesirable

gases that might be present. Fast air currents(especially of dry air) should be avoided.

During the picking period, relative humidityshould be kept at 85-90% to prevent scaling anddrying out of the beds.

Cook outAt the end of cropping, it is good practice to cookout the compost using live steam to at least 70C

and maintaining it for up to 10 hours. Thisprevents the spread of pests and diseases fromold to new crops.

Crops at different stages of production shouldbe separated to prevent spread of pests anddiseases from old to newer crops. Good HygieneIs Essential In Mushroom Production.

ESTABLISHMENT COSTS

The price obtained by growers for their productvaries, depending on grade, quality, market supplyand demand. However, the range of variation isnot as great as that experienced in many othercrops. Industry averages over recent years have


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been in the range: Buttons, $2.80 - $4.00/kg;Cups, $2.50 $3.50/kg; Flats, $2.00 $2.80/kg;Factory, $1.60/kg (varies according to grade andcontract arrangements). The downside of this isthat the margins for growers are very slim andonly efficient producers will survive.

Costs of production vary according to the

growing system used and the scale of production.Over recent years, industry averages come outaround $2.75 - $ 3.25 per kg. However, thesefigures can only be a very rough guide, as theymake no allowance for borrowing costs, landpurchase, market conditions and overheadestablishment costs.

In setting up a mushroom farm, costs of thefollowing factors need to be taken into consideration:

land (minimum size about 1 ha) foundations and cement slab and drainage structures - for growing, work and storage

area, packing room power and wiring, steam boiler and pipes,

insulation air conditioning and duct work trays for peak heating and growing coolroom forklift

water supply spray pump and watering equipment casing mixer office staff amenities thermometers - remote for peak heat thermometers - for growing rooms tools, knives, maintenance

picking trolleys protective clothing and equipment for chemi-cal application

Farms where compost is made would also require:

reinforced concrete wharf with adequatedrainage and waste water recirculation anddisposal system

compost turning machine; good water supplyand reticulation

special thermometers with a scale of 10-90C storage area for raw materials (some

under cover) tractor and front end loader, odour control

mechanisms.

The most important items of cost to the mushroomgrower are:

structures and equipment

labour - for filling trays, spawning, casing,watering, emptying, harvesting, pickingand packing

compost casing spawn power and fuel - for air conditioners, boilers,

fork lifts, coolroom depreciation of plant and equipment chemicals, (disinfectants, fungicides,

insecticides) marketing costs cartons, transport, agents fees repairs and maintenance miscellaneous including telephone, rates,

bank costs


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This conflict has impacted on the mushroomindustry as a result of the substrating process.Odour is an unavoidable result of the productionof mushroom substrate (indeed substrating ingeneral). Substrate production has becomeincreasingly capital intensive. This has led to areduction in the number of substrate producersover recent years, as farmers decided not to pro-

duce their own substrate but to buy this in fromspecialist substrate producers. This trend wasobviously influenced by an awareness of the pos-sibility of objections to odour produced during thesubstrateing process.

At the present time, four substrate producersmake mushroom substrate for most growers inNSW. In other states, it is more usual for eachgrower to make substrate on-site. Most of theseproducers are introducing new state of the art

technology in an attempt to address the odourissue. However, recent court decisions havethreatened the continuation of substrating in itscurrent form. This is a significant and very realthreat to the NSW mushroom industry which willalso have major impacts on surrounding commu-nities and other rural activities in similar areas.

RESEARCH

The Australian mushroom industry has a strong

commitment to research and funds a significantprogram of research in

conjunction with theH o r t i c u l t u r a l

Research andDevelopmentCorporat ion.A five-yearindustry R&Dplan guides

d e c i s i o n sabout projectsto be undertaken.

INDUSTRY OUTLOOK

The AMGA regularly develops and reviews fiveyear plans for the industry and for marketing andR&D. The current plan sets the path for activitiesuntil the year 2000.

Production will continue to increase and so moreeffort will need to be put into marketing and

promotion. Research projects currently underwaywill assist with improving presentation of productto consumers.

Niche markets will also expand, as productionof specialty mushrooms increases and morevalue-added products are made available.

Documents

Intro Growing