Lec. 5 Casing Soil in button mushroom cultivation.pdf

Casing soil in button mushroom cultivation

1. WhatisMushroomCasingsoil?
Itisthelastlayerofmediaincommercialmushroomgrowth.
Peatisusedasitwillhold10timesit'sownweightinmoisture,andmushroomsthrivein
thisenvironment.Casingisanaturalenvironmentformushroomstogrowin.
Casingalsogivesthemushroomavibrantnaturalcolorwhichmanyothermediadonot
give.
Mushroomcasingconsistsofablendofwetpeatswhichareneutralized.Therearemany
differentmushroomgrowingsystemsthroughouttheworld,frommushroombaggrowing
systems,mushroomtraysystemsandMushroomShelfsystems.Whatallthesesmushroom
growingsystemshaveincommonistheyalluseMushroomCasingSoils.
Casing:
Thecompostbedsaftercompletespawnrunshouldbecoveredwithalayerofsoil(casing)
about3-4cm.thicktoinducefruiting.
Thecasingmaterialshouldbehavinghighporosity,waterholdingcapacityandthepH
shouldrangebetween7-7.5.Peatmosswhichisconsideredtobethebestcasingmaterialis
notavailableinIndia,assuchthemixtureslikegardenloamsoilandsand(4:1);decomposed
cow-dungandloamsoil(1:1)andspentcompost(2-3yearsold);sandandlimearecommonly
used.
Thecasingsoilbeforeapplicationshouldbeeitherpasteurized(at66-70
0
Cfor7-8hours),
treatedwithformaldehyde(2%)andbavistin(75ppm)orsteamsterilized.Thetreatment
needstobedoneatleast15daysbeforethematerialisusedforcasing.
Aftercasingisdonethetemperatureoftheroomisagainmaintainedat23-28
0
Cand
relativehumidityof85-90%foranother8-10days.LowCO
2concentrationisfavourablefor
reproductivegrowthatthisstage.

2. Amongthestagesofmushroomcultivation,theadditionofthecasinglayeris
essentialtoachievehighproductivity.
Thecasinglayeristhematerialusedtocoverthemushroomcompostafter
completecolonizationtoinducethetransitionfromvegetativetoreproductive
growth.
However,itshouldbenotedthatthisstepisnotmandatoryforallmushroom
species,beingessentialforAgaricusmushroomsandoptionalforPleurotusspp.
andCoprinuscomatus.
Theinductionoffruitingisgeneticallycontrolledbutalsostronglyinfluencedby
environmentalfactors.Duetothelargedifferencesbetweenthephysicochemical
propertiesofthecasinglayerandthecompost,coveringthecompostwithsucha
differentmaterialtriggersatransitionfromvegetativefungalgrowthtothe
reproductiveprocess.
Thecasinglayerthereforepromotesanecologicalchangethatisdecisiveinthis
transitionandisasimportantasthequalityofthecompostandthemanagementof
cultivationconditions.
Thus,theinductionoffruitingdependsnotonlyonthegeneticcapacityofthe
myceliumbutalsoonphysical,chemicalandmicrobiologicalfactors.
Inthiscontext,thecasinglayerisoneofthemostimportantaspectsofmushroom
productioninfluencedbythesefactors,inadditiontotheimportantparametersof
temperatureandrelativehumidity.

3. Whyiscasingsoilused?Therearetwomainreasons:
1.thePseudomonasputidabacterium;
2.toregulateevaporation.
•Theimportanceofmicrobialinteractionsforthefruitingofmushroomshasbeendocumented
formanyyears.Formycorrhizalmushrooms,inadditiontomicrobialinteractionswithplant
rootsbeingimportant,themicrobialcommunitypresentinthefungalmantleplaysavitalrole
inthefruitingprocess.Forcultivatedmushrooms,interactionswithothermicroorganisms
alsooccur,wherebacteriapresentinthecasinglayerstimulatefruiting.Severalspeciesmay
playthisroleinparticular,studieshavedemonstratedtheparticipationofPseudomonas
putida.
•However,subsequentstudieshaveshownthatamixtureofPseudomonasspeciesorother
bacterialgroupsisactuallymoreeffectivethanasinglespeciesinstimulatingfruiting.
Accordingtothesestudies,thesebacteriaactinthedegradationofvolatilecompoundsthat
inhibitprimordialformation.
•Mushroomswillnotgrowwithoutevaporation.Thecasingsoilstructure,throughthedepthof
casingandonthesurface,isthefactorthatdetermineshowmuchwatercanabsorbedand
released.Thisisalsoknownasthewaterbuffer.

4. Properties
Casingsoilismadeupofpeat.Peatconsistofmanysmallandlargerporeswhichactas
communicatingstructuresthataffecttheflowofwater.Theverytiny(micro)poresabsorb
waterveryslowly,butretainitforalongtime.Thelarger(macro)porescanabsorbwater
fasterbutreleaseitagainveryquickly.
Ingoodcasingsoil,bothpropertiesarenecessary:rapidabsorptionofwater:duringmycelium
growthandafterharvesting,andslowrelease:duringpinheadformationandoutgrow,and
whenthemushroomsareharvested.
Physicalandchemicalfactors,suchasparticlesize,electricalconductivityandpH,are
considereddeterminantsofthequalityofthematerialusedasacasinglayer.Particlesizehas
adirecteffectonthecompactioncapacityofthecasinglayerand,consequently,onitswater
retentionandaerationcapacity.Ifthecasinglayerhashighelectricalconductivity,mushroom
fruitingisinhibitedordrasticallyreduced.RegardingpH,althoughfungicangrowina
slightlyacidicenvironment,thecasinglayershouldhaveanalkalinepHofuptopH8.0.The
useofneutraloralkalinepHinthecasinglayerisimportantnotonlyforthephysiologyofthe
fungusbutalsotohelpcontrolthepresenceofcompetitorssuchasTrichoderma,whichgrow
betteratacidicpH.Duetoallthesefactors,materialsarerarelyusedinpureform,being
combinedinsteadwithothermaterialsorcorrectivematerialstoachievedesirableproperties
inthecasinglayer,especiallyintermsofpHandporosity.

5. Air
Whatisthesecretofcasingsoil?Ensurethatthemoisturecontentofthecasingsoilisgood.
With“export”casingsoil,wehavetoapplyenoughwaterandmixthecasingwithaloaderor
bobcat.
Askthesupplierforinstructionsandfollowthemcorrectly.Casingsoilissensitiveto
structurelossjustbeforeitisapplied.Ifthecasingsoiliscompactedorcompressed,the“air”
willbesqueezedout.Thiseffectivelyclosesofftheverycrucialmicropores.Thecasingsoil
willfeelharder.Duringtransportandfillingavoidcompactingthecasingsoiltoomuch,for
examplewhenusingaugers,over-fillingthehopperonthefillerorinfrontofthelevelingaxle
duringfilling.
Soft
Casingsoilshouldfeelniceandsoft.Straightafterfilling,pushyourfingerintothecasing
soil.Weshouldbeabletoplungeyourfingerineasilyandwithoutresistance.Experience
teacheshowtofeelthedifference.
Agoodlayerofcasingsoilafterfillingisabout6cmthick.Theamountorderedismuchless,
around4.5cm.Therestisair,andtheseairpocketscanlargelybefilledwiththewater
necessaryforthemushroomstogrow

6. Casingandcaserun
•Casingisa3-4cmthicklayerofsoilappliedontopofspawnruncompostandisapre-
requisiteforfructificationinA.bisporus.
a.Casingmaterials
•Earliersub-soilmaterialororganicmatterrichsoilswereusedascasinginbuttonmushroom
cultivation.Presentlypeatisthemostdesirablecasingmaterialusedworldwidewith
excellentmushroomyieldsandsuperiorfruitbodyquality.However,pestisnotavailablein
India.Theotheralternativerecommendedmaterialsare,
1.WelldecomposedFarmYardManure(FYM)preferablytwoyearsold
2.WelldecomposedSpentMushroomCompost(SMC)(twoyearsoldanaerobically
decomposed)
3.Compostedcoirpith(coirindustrywaste)(welldecomposed&waterleached)
4.1:1,2:1and1:2,v/vofwelldecomposedFYMandSMC
5.1:1,v/vofdecomposedFYMorSMCwithcompostedcoirpith
6.Decomposedpowderedbarkofsomeforesttrees
7.Paperindustrywaste
8.BurntricehuskisalsoinusealongwithdecomposedFYM(2:1,v/v)inseasonal

7. Quality of casing materials
•Soft texture
•Light weight
•High water holding capacity
•High porosity
•Deficient in available form of C and N
•Neutral pH (7.0 –7.5)
•Low conductivity (400-600 μ moh)
Casing treatment
Casing material should be treated properly before its application on the spawn run compost
and the steps involved are:
•Make a heap of casing material
•Wet it up to 50-60% water holding capacity
•Fill in trays and shift them to pasteurization chamber
•Steam pasteurization at 60-65°C for 6-8 hours
•Auto-Cooling

8. Alternatively,
•Makeaheapofcasingmaterialonacementedplatform
•Wetitupto50-60%waterholdingcapacity
•Drenchthewetcasingwithformalin@1litre/m3(40%formaldehyde)bymixingwithshovel
•Coveritwithpolythenesheetandsealtheouterperipherythereafterbypouringsand/soilon
outsidemargin
•Keepthematerialfor24-48hoursinsunforfumigationeffect
•Removethecoverafter48handexposethematerialtoopenairandsunlightbyspreading
overwithcleantoolsandpermittingtheformalinfumestoescapeintoairfor2-3daysbefore
itisusedascasing(formalintreatmenteffectdecreasesatlowtemperatureduetoinadequate
fumigation)
Casingapplication
•Unfoldthefullyspawnrunbagandmakethetopsurfaceevenbygentlepressingwithhands
•Lightsprayofwateronspawnruncompost
•Applicationof4-5cmthicklayerofcasinguniformlyusingironringsof4cmheightor
woodenblocks
•Watersprayininstallmentsimmediatelyaftercasingapplication

9. Caserunandpinheadformation
Caserunisdoneatatemperatureof24±1°C,RH-95%andCO2>7500ppm
(straindependent)foraboutoneweek.
Thereisnorequirementforfreshairintroductionduringcaserun.
Itisconsideredcompletewhenmyceliacomeinthevalleysofcasinglayer.
Aftercaserun,theenvironmentalconditionsarechangedbybringingdownthe
temperatureto15-17°C(air),RHto85%andCO2to800-1000ppm(strain
dependent)byopeningofthefreshairventilationandexhaustingCO2.
Thischangeinenvironmentalparametersinducespinheadformationin3-4days
(straindependent)time.Thepinheadsdevelopintosolidbuttonsizedmushroomsin
another3-4days.
Atthisstage,theairinsidethecroppingroomischanged4-6timesinanhourto
maintainappropriateCO2conc.asCO2productionisatitspeakduringfirstflush
(actuallypeaksatcaserun).