Conditioning Soil with Pumice
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Pumice serves as an effective long-term soil conditioner by improving soil structure, mitigating compaction, and retaining moisture and nutrients. It enhances root zone function, supports plant growth, and is beneficial for various agricultural practices, making it ideal for engineered soils and lightweight applications. Additionally, pumice's environmentally friendly nature and cost-effectiveness compared to manufactured soil amendments position it as a preferred choice for gardeners and landscapers.
![Conditioning Soil
withPumice
K N O W L E D G E B R I E F
close-up of a 1-inch pumice stone
crushed pumice (G2) at 100x magnification
(208)766-4777x111
email:rd@hesspumice.com
www.hesspumice.com
Pumice, by virtue of its natural structure (best described as a
foamed stone), makes an ideal soil conditioner for those looking to
permanently improve root zone structure, mitigate compaction,
and retain moisture and nutrients.
FORASLONGasmanhasbeencultivating
andplanting,hehasunderstoodthe
importanceofconditioningthesoil—
eitherbyaddingneedednutrients,byimprovingpoornativestructure,orboth.Organiccomposts
workwonderfully,butforpoorsoilsthatneedtobestructurallyamended,organicsarenota
long-termsolution.Instead,aclassofinorganicamendmentscanbeusedtoengineerpermanent
performancestructureintosoils.Pumice,byvirtueofitsnaturally-occurring,foamed-stonestructure,
makesanideal,long-livedsoilamendment.Evencrushedtosoil-blendingparticlesize,pumiceretains
itslight,frothy,functionalcharacter,contributingtosoilperformanceinthefollowingways:
IMPROVES SOIL STRUCTURE. Afunctionalrootzoneiscriticaltosupportvibrant,deep-rooted
plants.Forexample,heavyclaysoils,consistingofatightmatrixofplate-likeparticles,offerapoor
growingmediumifnotamended.Thefertilitymaybethere,butthestructureiswrong.Addingpumice
physicallydisruptsclay’stendencyforcompaction,forcingapartthedense,stickyparticlesand
improvingthesoil’sabilitytobreath,absorbanddrainwater,filterrunoff,andsupportlushvegetation.
Astudy1 publishedintheJournalofCentralEuropeanAgriculture(2005)measuredstrawberry
seedlinggrowthinpumice-amendedsoil(at15,30,and45%amendmentlevels)anddetermined
“importantlevel”increaseingrowth,attributedtothestudiedenhancedmoistureretentionandpore
sizedistributionfactorscontributedbythepumiceamendment,especiallyat45%amendmentratio.
Anotherstudy2 concluded“thatpumicemaybeeffectivelyusedinspecificamountsforimproving
aerationandbulkdensityconditionsofpoorlystructuredsoils.”
IMPROVE SOIL SUBSTRUCTURE. Creatingorrepairingcompactedsubsoilstructureisas
essentialtocropproductivityasisamendingtheuppersoilarea.Openingupsubsoilporespacemeans
vegetativevitalityisnotrestrictedbypooraerationanddrainage.Workingpumiceintothesubsoil
lightenssoildensity,allowingdeeperaerationandmicrobialaction,whichinturnbringsgreaterroot
massanddepth.
KEYCHARACTERISTICSof
HESSPUMICE:
■ Specificgravityweightof2.35
■ Lowunitweight:40-50lbscubic
foot(dependingongrade)
■ MOHS-scalehardness:6
■ pHneutral:7.2
■ Duetoitsamorphouscharacteristics,
pumiceisnotconsideredahealthriskto
theworkerswhohandleit.
■ Chemically,pumiceisprimarilySilicon
Dioxide(AmorphousAluminumSilicate),
someAluminumOxide,andtraceamounts
ofotheroxides.
[1] Effect Of Pumice Amendment On Physical Soil Properties and Strawberry Plant Growth.
Ustun SAHIN, Selda ORS, Sezai ERCISLI, Omer ANAPALI, Ahmet ESITKEN; Atatürk University, Department of Agricultural Structures and Irrigation, Erzurum-Turkey
[2] Addition of Pumice Affects Physical Properties of Soil Used for Container Grown Plants.
Ustun SAHIN, Omer ANAPALI; AgriculturaeConspectusScientificus (ACS) 01/2006; 71(2)](https://image.slidesharecdn.com/conditioning-soil-with-pumice-180131201029/85/Conditioning-Soil-with-Pumice-1-320.jpg)
![C O N D I T I O N I N G S O I L W I T H P U M I C E | 2
MITIGATES COMPACTION.
Becausethefoamy,pore-richnatureof
pumiceisinherentlystructural,muchofthe
compactionresistantbenefitof
pumice-blendedsoilscomesfromthe
matrixoftinypumicestonesthemselves.
Thatmeansdesirablefactorslikerootzone
airexchangecapacityandmoisture
retentionarenotwhollyreliantonthe
spacesbetweensoilparticles.Andthe
grippynatureofthepumicegranules
stabilizessurroundingsoilparticles,greatly
increasingresistancetothecompressive
forcesofcultivation,watering,harvesting
and,inthecaseofturf, footandcarttraffic.
RETAINSWATER AND NUTRIENTS. Frothypumicegranules
grabandholdwaterandnutrientsandthengivethembacktothesoil
(androots)overtime.
TheAustralianJournalofCropSciencepublishedastudy3 thatlooked
ataddingpumicetoachievegainsinsoilmoistureabsorptionand
retentionformaize(corn)crops.Theresultsshowedthat“pumice
significantly(p>0.05)increasedtheamountofsoilmoistureretention
comparedtocontrol.Growthcharacteristicsofmaize(vegetativegrowth
andyield)weresignificantlyimprovedwithincreasingamountof
pumiceconcentration”withthemaxresultsobtainedwiththe30%
pumiceapplication.
CREATES ELEMENTALTILTH. Mixingpumiceintopoornative
soilstransformsthesoilstructureonanelementallevel,restructuring
thesoilmatrixanddiversifyingtheporesizestocreatemorefavorable
conditionsforseedgerminationandrootproliferation.Thistypeoftilth
iselementalandenduring,unlikethetemporary,unstabletilthcreated
solelybytillagepractices.
ENGINEERED SOILS
Engineeredlandscapes—reclamationprojects,runoff-filteringecology
embankments,drainageandstormwatercontrollingcontours,
constructedwetlands,high-trafficparksandsportsfields—demand
fine-tunedsoilsdesignedtooptimizeperformance.Theseprojectsare,
ofnecessity,fix-and-forgetprojects,andifthesoilprofileisnot
improvedinthelong-term,4 mostfailin
sustainingtheplantlifethatisseededin
them.Engineeringproperlong-termsoil
structureandwater-holdingand/or
drainagecapacityincreasestheoddsof
successsignificantly.Pumiceistheideal
inorganicfoundationamendmentupon
whichtobuildthesetypesoflarge-scale
constructs,asthesoil-enhancingbenefits
ofpumicecanberealizedwithalittleasa
10%pumice-to-soilratio.
A LIGHTWEIGHT SOIL
AMENDMENT. Thefrothy-stone
characterofpumicemakesitanideal
lightweightamendmentforroof-gardensandotherweight-sensitive
grow-bedapplicationslikelargepotsandraisedplanterbeds.In
greenhouseculture,alowerbulkdensityisdesirableduetoeasier
handlingandlessrootlossduringpickupandtransportation.
PUMICE-BLENDED COMPOST
Thebeautyofpumice-blendedcompostisthatlongaftertheorganic
matterisconsumed, thepumiceremains,afunctional,physical
presenceimprovingthesoilprofile.
Inlarge-scalefix-and-forgetrevegetationprojectslikethose
mentionedabove,repeatcompostapplicationsarenotpossibleor
feasible. Thatbecomesespeciallyproblematicwhenthecompostwas
usedasarestructuringagentinthesoilandnotsolelytoprovidea
kick-startingnutrientandmicrobialcharge.
Pumice-enhancedcompostprovidesrevegetationcontractorswith
aviable,cost-effectivepre-seedingsolutiontobothenrichthesoiland
amendstructurallypoorordamagedsoilstoachievelong-term,
self-sustainingvegetativecover.
Pumice-blendedcompostisavalue-addedproductforregionswith
poororproblematicnativesoils—asthepumice-enhancedcompostis
applied,aresidual,cumulativeimprovementistakingplaceindefinite-
ly—animprovementthatcontinuestobuildcycleaftercycle.Whenthe
physicalsoilstructureisfinallydeemedideal,thepumice-enhanced
formulationcanbediscontinued.
[3] SoilWater Retention and Maize (Zea mays L.) Growth as Effected by Different Amounts of Pumice.
Ashraf Malekian, EinollahValizadeh, Mona Dastoori, Sohaila Samadi,Vahid Bayat; Department of Agriculture, Payame Noor University, PO Box 19395-3697,Tehran, Iran
[4] Shortcomingsof Native Seeding Project Implementation;Western Chapter of IECA Newsletter, Spring 2006](https://image.slidesharecdn.com/conditioning-soil-with-pumice-180131201029/85/Conditioning-Soil-with-Pumice-2-320.jpg)
![C O N D I T I O N I N G S O I L W I T H P U M I C E | 3
OTHER CONSIDERATIONS
BLENDING. Theuniformityofthepumicesoil-amendmentgrades
makesqualitycontroleasyduringtheblendingoperation,aspumiceis
dryandflowable.
TOP DRESSING FORTURF. Asatopdressingforexistingturf
lawnsandplayingsurfaces,pumiceout-performssandforenhancingair
andwatermovementintherootzone,holdingontomoistureand
nutrients,resistingcompactionforces,andsupportingbeneficialsoil
microorganismsthatbreakdownthatchandenrichthesoil.Pumicealso
readilymixeswithcompost,peatmoss,sand,andsoilsinblended
topdressingapplications.
PUMICEVS. MANUFAC-
TURED SOIL AMENDMENTS.
Thepracticeofblendingbitsoflight,
frothyrockwithgrowingsoilsis
alreadyawell-establishedpracticein
themarketplace.Thereareseveral
productsonthemarketdesignedto
mimicthestructuralcharacterand
in-soilperformanceofpumice—
materialssuchasexpandedperlite,
expandedvermiculite,expandedclays
(likeHydrockTM)andexpandedshale
(suchasPerma-TillTM
andUteliteTM).
Notetheuseoftheword“expanded”
witheach.Theoresfortheseproductshavetoundergoanenergy-inten-
sivesuperheatingprocessthatexpandsorpuffstheoretoitsuseful,
pumice-likestate.Pumice,ontheotherhand,wassuperheatedina
volcanoandfoamedwhenejectedintotheatomsphere.
Pumice,initsnaturalminedstate,improvessoilstructurewithout
theenvironmentalimpact/fuelburnandprocessingcostsofthe
expandedproducts.Thisfactnotonlymakespumicethegreenchoice
butalsomakespumicetheeconomicalchoice—bringingitinata
quarter-to-halfthepriceofexpandedperlite,forexample.Thatyields
significantvalue,especiallyinlarge-scaleapplications.
PUMICE AND PERLITE: PHYSIOCHEMICALTWINS.
Perliteiswidelyusedinhorticulture,especiallyinpottingandgarden
soils.Itisvaluedforitscontributiontodesirablesoilstructureandwater
andnutrientretention.Buttheprocessofflash-heatingperliteoreto
expanditaddstothecostandthecarbonfootprintofperlite.
AUniversityofIllinoisstudy5 evaluatedpumiceas
aperlitesubstituteforamendingsoil.Specifically,chemicalproperties
andsurfacecharacteristicswerecomparedandprovedanalogous,with
pumiceexhibitingagreaterporesizespan.Fromthereportsummary:
“Pumiceandperlitewereshowntohavesimilarphysicochemical
propertieswhichsubsequentlytranslatedintosimilarbehaviorin
blendedsoilmixtures.Itproved
equally,ifnotevenmoreeffective
insomeways,thanperlite.
Asubsequentcompanionplant
growthstudy(notreportedherein)
furtherconfirmedthesuitabilityof
pumiceasasoilamendment.Plants
grewequallywellinpumiceand
perlitemedia.”
HESS PUMICE
PRODUCTS
Pumiceisfoundallovertheworld,but
thequality,physicalcharacteristics
andchemicalcompositionvaryfrom
deposittodeposit.TheHesspumicedepositinsoutheastIdahois
recognizedasthepurestcommercialdepositofpumiceontheplanet,
andHessrefinesandshipsthatpumiceworld-wideforuseinvarious
industrialandagriculturalprocesses.HessPumiceProductshasbeen
miningandrefiningthischoicepumicedepositsince1958andenjoysa
well-earnedreputationforgettingitwhereitneedstobeon-timeand
on-spec.
SoilRoxHorticulturalPumiceisavailablein2.5lb.bags,20lb.boxes,
supersacksorshippedinbulkviatruckortraincars.
[5] Evaluation of Pumice as a Perlite Substitute for Container Soil Physical Amendment.
Dianne A. Noland , L. Art Spomer & David J.Williams; Department of Horticulture, University of Illinois, 1201 South Dorner Drive, Urbana, 61801–4720
www.soilrox.com](https://image.slidesharecdn.com/conditioning-soil-with-pumice-180131201029/85/Conditioning-Soil-with-Pumice-3-320.jpg)
Conditioning Soil with Pumice
- 1. Conditioning Soil withPumice K N O W L E D G E B R I E F close-up of a 1-inch pumice stone crushed pumice (G2) at 100x magnification (208)766-4777x111 email:rd@hesspumice.com www.hesspumice.com Pumice, by virtue of its natural structure (best described as a foamed stone), makes an ideal soil conditioner for those looking to permanently improve root zone structure, mitigate compaction, and retain moisture and nutrients. FORASLONGasmanhasbeencultivating andplanting,hehasunderstoodthe importanceofconditioningthesoil— eitherbyaddingneedednutrients,byimprovingpoornativestructure,orboth.Organiccomposts workwonderfully,butforpoorsoilsthatneedtobestructurallyamended,organicsarenota long-termsolution.Instead,aclassofinorganicamendmentscanbeusedtoengineerpermanent performancestructureintosoils.Pumice,byvirtueofitsnaturally-occurring,foamed-stonestructure, makesanideal,long-livedsoilamendment.Evencrushedtosoil-blendingparticlesize,pumiceretains itslight,frothy,functionalcharacter,contributingtosoilperformanceinthefollowingways: IMPROVES SOIL STRUCTURE. Afunctionalrootzoneiscriticaltosupportvibrant,deep-rooted plants.Forexample,heavyclaysoils,consistingofatightmatrixofplate-likeparticles,offerapoor growingmediumifnotamended.Thefertilitymaybethere,butthestructureiswrong.Addingpumice physicallydisruptsclay’stendencyforcompaction,forcingapartthedense,stickyparticlesand improvingthesoil’sabilitytobreath,absorbanddrainwater,filterrunoff,andsupportlushvegetation. Astudy1 publishedintheJournalofCentralEuropeanAgriculture(2005)measuredstrawberry seedlinggrowthinpumice-amendedsoil(at15,30,and45%amendmentlevels)anddetermined “importantlevel”increaseingrowth,attributedtothestudiedenhancedmoistureretentionandpore sizedistributionfactorscontributedbythepumiceamendment,especiallyat45%amendmentratio. Anotherstudy2 concluded“thatpumicemaybeeffectivelyusedinspecificamountsforimproving aerationandbulkdensityconditionsofpoorlystructuredsoils.” IMPROVE SOIL SUBSTRUCTURE. Creatingorrepairingcompactedsubsoilstructureisas essentialtocropproductivityasisamendingtheuppersoilarea.Openingupsubsoilporespacemeans vegetativevitalityisnotrestrictedbypooraerationanddrainage.Workingpumiceintothesubsoil lightenssoildensity,allowingdeeperaerationandmicrobialaction,whichinturnbringsgreaterroot massanddepth. KEYCHARACTERISTICSof HESSPUMICE: ■ Specificgravityweightof2.35 ■ Lowunitweight:40-50lbscubic foot(dependingongrade) ■ MOHS-scalehardness:6 ■ pHneutral:7.2 ■ Duetoitsamorphouscharacteristics, pumiceisnotconsideredahealthriskto theworkerswhohandleit. ■ Chemically,pumiceisprimarilySilicon Dioxide(AmorphousAluminumSilicate), someAluminumOxide,andtraceamounts ofotheroxides. [1] Effect Of Pumice Amendment On Physical Soil Properties and Strawberry Plant Growth. Ustun SAHIN, Selda ORS, Sezai ERCISLI, Omer ANAPALI, Ahmet ESITKEN; Atatürk University, Department of Agricultural Structures and Irrigation, Erzurum-Turkey [2] Addition of Pumice Affects Physical Properties of Soil Used for Container Grown Plants. Ustun SAHIN, Omer ANAPALI; AgriculturaeConspectusScientificus (ACS) 01/2006; 71(2)
- 2. C O N D I T I O N I N G S O I L W I T H P U M I C E | 2 MITIGATES COMPACTION. Becausethefoamy,pore-richnatureof pumiceisinherentlystructural,muchofthe compactionresistantbenefitof pumice-blendedsoilscomesfromthe matrixoftinypumicestonesthemselves. Thatmeansdesirablefactorslikerootzone airexchangecapacityandmoisture retentionarenotwhollyreliantonthe spacesbetweensoilparticles.Andthe grippynatureofthepumicegranules stabilizessurroundingsoilparticles,greatly increasingresistancetothecompressive forcesofcultivation,watering,harvesting and,inthecaseofturf, footandcarttraffic. RETAINSWATER AND NUTRIENTS. Frothypumicegranules grabandholdwaterandnutrientsandthengivethembacktothesoil (androots)overtime. TheAustralianJournalofCropSciencepublishedastudy3 thatlooked ataddingpumicetoachievegainsinsoilmoistureabsorptionand retentionformaize(corn)crops.Theresultsshowedthat“pumice significantly(p>0.05)increasedtheamountofsoilmoistureretention comparedtocontrol.Growthcharacteristicsofmaize(vegetativegrowth andyield)weresignificantlyimprovedwithincreasingamountof pumiceconcentration”withthemaxresultsobtainedwiththe30% pumiceapplication. CREATES ELEMENTALTILTH. Mixingpumiceintopoornative soilstransformsthesoilstructureonanelementallevel,restructuring thesoilmatrixanddiversifyingtheporesizestocreatemorefavorable conditionsforseedgerminationandrootproliferation.Thistypeoftilth iselementalandenduring,unlikethetemporary,unstabletilthcreated solelybytillagepractices. ENGINEERED SOILS Engineeredlandscapes—reclamationprojects,runoff-filteringecology embankments,drainageandstormwatercontrollingcontours, constructedwetlands,high-trafficparksandsportsfields—demand fine-tunedsoilsdesignedtooptimizeperformance.Theseprojectsare, ofnecessity,fix-and-forgetprojects,andifthesoilprofileisnot improvedinthelong-term,4 mostfailin sustainingtheplantlifethatisseededin them.Engineeringproperlong-termsoil structureandwater-holdingand/or drainagecapacityincreasestheoddsof successsignificantly.Pumiceistheideal inorganicfoundationamendmentupon whichtobuildthesetypesoflarge-scale constructs,asthesoil-enhancingbenefits ofpumicecanberealizedwithalittleasa 10%pumice-to-soilratio. A LIGHTWEIGHT SOIL AMENDMENT. Thefrothy-stone characterofpumicemakesitanideal lightweightamendmentforroof-gardensandotherweight-sensitive grow-bedapplicationslikelargepotsandraisedplanterbeds.In greenhouseculture,alowerbulkdensityisdesirableduetoeasier handlingandlessrootlossduringpickupandtransportation. PUMICE-BLENDED COMPOST Thebeautyofpumice-blendedcompostisthatlongaftertheorganic matterisconsumed, thepumiceremains,afunctional,physical presenceimprovingthesoilprofile. Inlarge-scalefix-and-forgetrevegetationprojectslikethose mentionedabove,repeatcompostapplicationsarenotpossibleor feasible. Thatbecomesespeciallyproblematicwhenthecompostwas usedasarestructuringagentinthesoilandnotsolelytoprovidea kick-startingnutrientandmicrobialcharge. Pumice-enhancedcompostprovidesrevegetationcontractorswith aviable,cost-effectivepre-seedingsolutiontobothenrichthesoiland amendstructurallypoorordamagedsoilstoachievelong-term, self-sustainingvegetativecover. Pumice-blendedcompostisavalue-addedproductforregionswith poororproblematicnativesoils—asthepumice-enhancedcompostis applied,aresidual,cumulativeimprovementistakingplaceindefinite- ly—animprovementthatcontinuestobuildcycleaftercycle.Whenthe physicalsoilstructureisfinallydeemedideal,thepumice-enhanced formulationcanbediscontinued. [3] SoilWater Retention and Maize (Zea mays L.) Growth as Effected by Different Amounts of Pumice. Ashraf Malekian, EinollahValizadeh, Mona Dastoori, Sohaila Samadi,Vahid Bayat; Department of Agriculture, Payame Noor University, PO Box 19395-3697,Tehran, Iran [4] Shortcomingsof Native Seeding Project Implementation;Western Chapter of IECA Newsletter, Spring 2006
- 3. C O N D I T I O N I N G S O I L W I T H P U M I C E | 3 OTHER CONSIDERATIONS BLENDING. Theuniformityofthepumicesoil-amendmentgrades makesqualitycontroleasyduringtheblendingoperation,aspumiceis dryandflowable. TOP DRESSING FORTURF. Asatopdressingforexistingturf lawnsandplayingsurfaces,pumiceout-performssandforenhancingair andwatermovementintherootzone,holdingontomoistureand nutrients,resistingcompactionforces,andsupportingbeneficialsoil microorganismsthatbreakdownthatchandenrichthesoil.Pumicealso readilymixeswithcompost,peatmoss,sand,andsoilsinblended topdressingapplications. PUMICEVS. MANUFAC- TURED SOIL AMENDMENTS. Thepracticeofblendingbitsoflight, frothyrockwithgrowingsoilsis alreadyawell-establishedpracticein themarketplace.Thereareseveral productsonthemarketdesignedto mimicthestructuralcharacterand in-soilperformanceofpumice— materialssuchasexpandedperlite, expandedvermiculite,expandedclays (likeHydrockTM)andexpandedshale (suchasPerma-TillTM andUteliteTM). Notetheuseoftheword“expanded” witheach.Theoresfortheseproductshavetoundergoanenergy-inten- sivesuperheatingprocessthatexpandsorpuffstheoretoitsuseful, pumice-likestate.Pumice,ontheotherhand,wassuperheatedina volcanoandfoamedwhenejectedintotheatomsphere. Pumice,initsnaturalminedstate,improvessoilstructurewithout theenvironmentalimpact/fuelburnandprocessingcostsofthe expandedproducts.Thisfactnotonlymakespumicethegreenchoice butalsomakespumicetheeconomicalchoice—bringingitinata quarter-to-halfthepriceofexpandedperlite,forexample.Thatyields significantvalue,especiallyinlarge-scaleapplications. PUMICE AND PERLITE: PHYSIOCHEMICALTWINS. Perliteiswidelyusedinhorticulture,especiallyinpottingandgarden soils.Itisvaluedforitscontributiontodesirablesoilstructureandwater andnutrientretention.Buttheprocessofflash-heatingperliteoreto expanditaddstothecostandthecarbonfootprintofperlite. AUniversityofIllinoisstudy5 evaluatedpumiceas aperlitesubstituteforamendingsoil.Specifically,chemicalproperties andsurfacecharacteristicswerecomparedandprovedanalogous,with pumiceexhibitingagreaterporesizespan.Fromthereportsummary: “Pumiceandperlitewereshowntohavesimilarphysicochemical propertieswhichsubsequentlytranslatedintosimilarbehaviorin blendedsoilmixtures.Itproved equally,ifnotevenmoreeffective insomeways,thanperlite. Asubsequentcompanionplant growthstudy(notreportedherein) furtherconfirmedthesuitabilityof pumiceasasoilamendment.Plants grewequallywellinpumiceand perlitemedia.” HESS PUMICE PRODUCTS Pumiceisfoundallovertheworld,but thequality,physicalcharacteristics andchemicalcompositionvaryfrom deposittodeposit.TheHesspumicedepositinsoutheastIdahois recognizedasthepurestcommercialdepositofpumiceontheplanet, andHessrefinesandshipsthatpumiceworld-wideforuseinvarious industrialandagriculturalprocesses.HessPumiceProductshasbeen miningandrefiningthischoicepumicedepositsince1958andenjoysa well-earnedreputationforgettingitwhereitneedstobeon-timeand on-spec. SoilRoxHorticulturalPumiceisavailablein2.5lb.bags,20lb.boxes, supersacksorshippedinbulkviatruckortraincars. [5] Evaluation of Pumice as a Perlite Substitute for Container Soil Physical Amendment. Dianne A. Noland , L. Art Spomer & David J.Williams; Department of Horticulture, University of Illinois, 1201 South Dorner Drive, Urbana, 61801–4720 www.soilrox.com