Effect of urban biowaste derived soluble substances on growth, photosynthesis and ornamental value of Euphorbia x lomi

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ContentslistsavailableatScienceDirect

Scientia

Horticulturae

j o u r n a l ho me p ag e :w w w . e l s e v i e r . c o m / l o c a t e / s c i h o r t i

Effect

of

urban

biowaste

derived

soluble

substances

on

growth,

photosynthesis

and

ornamental

value

of

Euphorbia

x

lomi

Giancarlo

Fascella

a,∗

_,

_Enzo

_Montoneri

b

_,

_Marco

_Ginepro

c

_,

_Matteo

_Francavilla

d

a_Consiglio_per_la_Ricerca_in_Agricoltura_e_l’Analisi_{dell’Economia}_Agraria,_Unità_di_Ricerca_per_il_recupero_e_la_{valorizzazione}_delle_Specie_Floricole Mediterranee.S.S.113-Km245.500,90011Bagheria(Palermo),Italy

b_Biowaste_Processing,_Via_XXIV_Maggio_25,₃₇₁₂₆_Verona,_Italy

c_Università_di_Torino,_Dipartimento_di_Chimica,_Via_Giuria_7,₁₀₁₂₅_Torino,_Italy d_STAR_Research_Group,_Università_di_Foggia,_Via_Gramsci,_89-91,₇₁₁₂₁_Foggia,_Italy

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received28June2015

Receivedinrevisedform22October2015 Accepted25October2015

Availableonline17November2015 Keywords:

Municipalbiowastesrecycling Leafchlorophyllcontent CO2exchangerate Plantphotosyntheticactivity Plantgrowth

a

b

s

t

r

a

c

t

Solublebio-basedsubstances(SBS)isolatedfrommunicipalbiowastesandacommercial Leonardite-basedproductwereappliedassubstratedrenchorasfoliarspraytogrowtheornamentalhybridEuphorbia xlomi.TheSBSwerefoundmorepowerfulthanthecommercialLeonarditeproductinenhancingplant photosynthesis,growthandaestheticeffect,improvingﬂowerquality,andoptimizingwateruse efﬁ-ciency.EnhancementfactorsofplantperformanceindicatorsbySBSrangedfrom1.3to8.6relativelyto thecontrolplants,andfrom1.2to4.5relativelytoplantstreatedwiththecommercialLeonarditeproduct atequalapplieddose.Theenvironmentalandeconomicimplicationoftheseresultsforagriculture,the managementofurbanwastes,andthechemicalindustryarediscussed.

1. Introduction

The management of urban wastes has become a priority

environmentalissue,duetoincreasingurbanizationandhuman

consumptionhabits.Theyrepresentasigniﬁcantcostforsociety.

Recentworkhashowevershownthatfermentedurbanbiowastes

areaviablesourceofsolublebio-basedsubstances (SBS)which

mayperformasefﬁcienteco-friendlychemicalauxiliariesin

diver-siﬁedﬁelds;e.g.,intheformulationofdetergents,textiledyeing

baths, ﬂocculants, dispersants and binding agents for ceramics

manufacture(Montonerietal.,2011), emulsiﬁers(Vargasetal.,

2014),auxiliariesforsoil/waterremediation(Avettaetal.,2013;

Gomisetal.,2014;Montonerietal.,2014)andenhancedoil recov-ery (Baxter etal., 2014), nanostructured materialsfor chemical (Boffaetal.,2014;Deganelloetal.,2015)andbiochemicalcatalysis (Magnaccaetal.,2012),plasticmaterials(Franzosoetal.,2015a,b,c),

soil fertilizersand plantbiostimulants for horticulture (Sortino

etal.,2014)andanimalfeedsupplements(Montonerietal.,2013;

Dinuccioetal.,2013).TheSBSareobtainedbyalkalinehydrolysis

oftheurbanbiowastespreviouslyfermentedunderanaerobicand

∗ Correspondingauthor.Fax:+39091909089.

E-mailaddresses:giancarlo.fascella@entecra.it,fascella@libero.it(G.Fascella).

aerobicconditions.Theyaremixtures ofmoleculeswith

molec-ularweightfrom5toseveral100kDa,comprisingaliphaticand

aromaticCatomsbondedtoavarietyofacidandbasicfunctional

groups.Thisisthelikelyreasonoftheirmultipurposeperformance.

Theabovestudiesprospectthesubstitutionofsynthetic

chem-icalsbySBSformanyapplications,andconsequentlythepotential

reductionofthedepletionoffossilsourcesandoftheaddedCO2

totheenvironmentcontributedbysyntheticchemicalsatlifeend.

Directenvironmentalimplicationsofthesesubstanceshavebeen

describedbySortinoetal.(2014)whohaveshownthatSBSadded

tosoil for horticultureenhance theplantphotosynthetic

activ-ity,growthand productivitymore thanthesourcingfermented

biowasteswithoutanyalkalinetreatment.ThesameSBSareproven

byAvetta et al.(2013)and Gomiset al.(2014) toenhancethe

photochemicaldegradationoforganicpollutantsinindustrial

efﬂu-ents.TheseﬁndingshavesuggestedthatSBSmaypromoteeither

Cﬁxationormineralization,accordingtothedifferentoperational

environments.Inbothcasesithasbeensuggestedthat,bytheir

capacitytocomplexFeionsandkeeptheminsolutionat

circum-neutral pH,theSBSmaycontribute toenhancea photo-Fenton

process.TheseﬁndingsproposeSBSasafriendlyinterfacebetween

plantandhumanactivities.

In thepresent workwe reporttheeffects of three products

containingorganicandmineralmatteronthephotosynthetic

activ-ity,growth,aestheticeffectand biomasswateruseefﬁciencyof

http://dx.doi.org/10.1016/j.scienta.2015.10.042

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ornamentalhybridEuphorbia x lomi Rauh(Euphorbia lophogona

Lamarck×E.miliiDesMoulins).Oneproductisacommercial

for-mulationtradedunderthenameofEnersoil,obtainedbyalkaline

hydrolysisofLeonardite(IntrachemBioItalia,2008).Theothertwo

productsareSBSisolatedfromthealkalinehydrolysateoftwo

fer-mentedbiowastematerials.Thesearethedigestate(DG)ofthe

biogasproductionreactorfedwiththeorganichumidrefuse of

separatesourcecollectionand the compost(CP)obtainedfrom

DGmixedwithprivateandpublicgardeningresidues,andsewage

sludge.TheCPandDGwereusedinthepreviousworkbySortino

etal. (2014)fortomato andpepper cultivation.Thepurposeof

thepresentworkwastoassesswhethertheeffectsreportedon

horticulturalspecieswereconﬁrmedalsoforornamentalplants.

Consistentlywiththeir sources,the investigated productshave

differentC, N and mineralcomposition, and thereforeallowto

evaluatetheeffectsofthedifferentnutrientscontentontheplant

performanceindicators.ThehybridEuphorbiaxlomiRauhplantwas

chosenastestplant,beingperennialandsomuchdifferentfrom

manyshort-cyclecropsastomatoandpepper.Theformerbelongs

totheSpurgefamilyandisasucculentshrubwithmilkylatex,long

lanceolateleavesandlargecoloredinﬂorescences,usually

culti-vatedaspottedﬂoweringplantorashedgeplantforlandscaping

andxerogardening(FascellaandZizzo,2009)becauseofitslow

exigenciesandtolerancetodroughtstress(Fascellaetal.,2011).

Theresultswereexpectedtoaddfurtherargumenttotheprevious

workonhorticulturalspecies(Sortinoetal.,2014)supportingthe

roleofSBSpromotingafriendlyCcycleintheecosystems.

2. Materialsandmethods

2.1. SBSandEnersoil

TheSBSwerepreparedandsuppliedbyStudioChionoed

Asso-ciati(SCA)inRivaroloCanavese(TO),Italy.Thiscompanyobtained

theSBSbyhydrolysisoftwofermentedurbanbiowaste

materi-alsaccordingtoa previouslyreportedprocedure(Sortinoetal.,

2014;Franzosoetal.,2015a,b,c).Theﬁrstmaterialwasthe

anaero-bicdigestate(DG)oftheorganichumidfractionofurbanwastefrom

separatesourcecollection.Thesecondmaterialwasthecompost

(CP)obtainedfromamixofDG,homegardeningandpark

trim-mingresiduesandsewagesludge,at3.5/5.5/1respectiveweight

ratio,whichwasagedunderaerobicconditionsfor110days.The

twofermentedurbanbiowastematerialswerefurtherprocessedby

SCAasfollows.TheDGorCPmaterial,separately,washydrolyzed

withKOHalkalinewateratpH13and60◦C.Thehydrolyzatewas

runthroughanultraﬁltrationpolysulphonemembranewith5kD

cutoff.Themembraneretentatewasdriedat60◦Ctoyieldthe

ﬁnalSBSproductasblacksolidina15–20%yield,relativetothe

startingmaterial.TheCPandDGSBScontained91and99%dry

mat-ter,respectively.ThecommercialEnersoilproductwassuppliedby

IntrachemBioinGrassobio(BG),Italy.

2.2. Greenhousefacilitiesandplantmaterial

Theplantgrowthtrialswereconductedin2013inanunheated

(28◦C day/14◦C night) double-span East–West oriented

green-house (34×16m) with steel structure and polyethylene cover

(thickness0.15mm),located at theResearch Unitfor

Mediter-raneanFlowerSpeciesnearPalermo(38◦5N,−13◦₃₀_E,₂₃_m_above

sealevel),ontheNorthWesternSicilycoastalarea.Sixmonths-old

8cm-tallmicropropagatedplantsofEuphorbiaxlomiRauhcv.

‘Ser-ena’weregrowninplasticpotsof13cmdiameter(1Lcapacity,1

plantperpot)ﬁlledwithasubstrateofsphagnumpeat(Dueemme

marketing,ReggioEmilia,Italy)andperlite(PerliteItaliana,Milano,

Italy)in1:1v/vratio.Water,macroandmicronutrientswere

sup-pliedtoplantsthrougha dripfertigationsystem(1dripperper

plant,2Lh−1)controlledbyacomputer.Allplantswerefedwith

thesamenutrientsolutionwhichhadthefollowingcomposition

(mgL−1):180totalN,50P,200K,120Ca,30Mg,1.2Fe,0.2Cu,

0.2Zn,0.3Mn,0.2B.ThepHandtheelectricalconductivity(EC)

ofthenutrientsolutionweremaintainedat5.8and1.8mScm−1,

respectively.Irrigationschedulingwasperformedusingelectronic

low-tensiontensiometersconnectedtoanelectronicprogrammer,

thatcontrolledirrigationbasedonsubstratematricpotential.The

SBSandEnersoilmaterialsweredissolvedordilutedinwaterto

yieldﬁvesolutionswiththefollowingdrymattergL−1

concentra-tions:45.5CP,31and15.5DG,18.7and9.4Enersoil.Analiquot

of100mlofeachsolutionwasappliedassubstratedrenchoras

foliarspraytoeachplant.Foliarspraysanddrenchesapplications

wereprovidedtoplantstwotimesduringthetrial(120days).The

totalappliedamountsofdrymattergperplantwere4.6forCPas

substratedrench,3.1and1.5forDGassubstratedrenchandfoliar

spray,respectively,and1.9and0.94forEnersoilassubstratedrench

andfoliarspray,respectively.

2.3. Plantgrowthmeasurements

Tenplants pertreatment, randomlychosenfromeach

repli-cate, were harvested every 30 days and separated into stems,

leavesand rootsfor growthmeasurements(plant height,

num-berofleavesperplant,numberofﬂowersperplant).Plantheight

was determined as the distance from the surface of the

sub-strate to thetop of theplant. Dry weight of the biomass was

determinedafter72hinaforced-airoven(at100◦C)when

har-vestedtissuesreachedaconstantvalue.Shoottorootratio(S/R)

wascalculatedbydividingsumofleafandstemdryweightsby

theroot dry weight.Leaf area(LA)was measuredusinga

dig-italareameter (WinDIAS 2;DELTA-T DEVICES Ltd.,Cambridge,

U.K.).RelativeGrowthRate(RGR)wascalculatedaccordingwith

theformulaproposedbyHoffmannandPoorter(2002)usingthe

followingequation:(lnW2−lnW1)/(t2−t1)whereln=natural

log-arithm,W1=dryweightofplantattimeone(ingrams),W2=dry

weightof plantattime two (ingrams),t1=time one (indays),

t2=timetwo(indays).BiomassWaterUseEfﬁciency(WUE)was

calculatedastheratiobetweentotaldryweightofplantsandplants

totalwatersupply.

2.4. LeafSPADindex,colorandgasexchangesmeasurements

Leafchlorophyllcontent(e.g.,SPADindex)ofthreerandomly

selectedleavesofallplantsineachexperimentalunitwas

mea-suredwithachlorophyllmeter(SPAD502,KonicaMinoltaSensing,

Inc.,Osaka,Japan).Leafcolorwasdeterminedwithashotinthe

middle ofthe bladeonthree leavesofall plantsof each

treat-mentwithacolorimeter(MinoltaCR10,KonicaMinoltaSensing,

Inc.,Osaka,Japan)thatcalculatedthecolorcoordinates(CIELAB):

lightness(CL),tone(CA)andsaturation(CB);CLvariesfrom0

(com-pletelyopaqueorblack)to100(completelytransparentorwhite);

CArangesfrompositive(redness)tonegative(greenness)values,

aswellasCB(positiveisyellowness,negativeisblueness).Leafgas

exchanges(netassimilationCO2(ACO2)andstomatalconductance

(gs))werealsomeasuredusingaportablephotosynthesissystem

(LI-6200;LI-CORInc.,Lincoln,NE,USA).Measurementsweremade

onmostrecentfullyexpandedleavesbetween10:00and13:00h

onsunnyday,usingﬁve replicateleavesper treatment.The

LI-6200wasequippedwithastirredleafchamberwithconstant-area

insertsandﬁttedwithavariableintensityredsource(leaf

temper-aturechamberwas30±2◦C,leaf-airvaporpressuredifferencewas

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Table1

AnalyticaldataforSBSandEnersoil.

SBS pH Volatilesoilds(w/w%a₎ _C_(w/w%a₎ _N_(w/w%a₎ _C/N _MW_(kDa)b _MW/MNb

DG 10.5 71.5±0.9 43.1±0.4 6.67±0.08 6.5 164 1.9 CP 10.1 67.6±0.2 40.2±0.1 5.22±0.05 7.7 75 1.5 Enersoilc _10.0 _60.0 _30.0 _0.20 ₁₅₀ – Mineralelementsd Si Fe Al Mg Ca K Na Cu Ni Zn Cr Pb P2O5 DG 0.25 0.52 0.10 0.27 2.08 1.59 0.19 262 24 361 15 46 1.14 CP 0.51 0.83 0.12 0.43 2.59 1.79 0.20 269 62 307 24 94 1.44 Enersoile _0.22 _0.10 _0.14 _0.38 _0.39 _4.92 _3.15 _2.98 _1.30 _2.56 _1.30 _0.71 _0.54

Ctypesandfunctionalgroupse_{concentration}_as_mole_fraction_of_total_organic_Cf

Af NR OMe OR OCO Ph PhOH PhOY COOH CON CO Af/Ar LH

DG 0.43 0.10 0.04 0.10 0.03 0.10 0.02 0.01 0.07 0.09 0.01 3.3 9.3

CP 0.31 0.08 0.00 0.20 0.07 0.16 0.06 0.02 0.09 0.01 0.00 1.3 5.3

Enersoilg _0.31 _0.00 _0.03 _0.09 _0.04 _0.31 _0.02 _0.08 _0.07 _0.02 _0.03 _0.76 _7.3

a_{Concentration}_values_referred_to_dry_matter:_averages_and_standard_deviation_calculated_over_triplicates.b_MW₌_weight_average_molecular_weight;_MN₌_number_average molecularweight.

c _Vendor_data₍_Intrachem_Bio_Italia,₂₀₀₈_). d _Si,_Fe,_Al,_Mg,_Ca,_K,_N,_P

2O5,as%w/w;Cu,Ni,Zn,Cr,Pb,Hgasppm. e_Data_obtained_in_this_work.

f _Aliphatic_(Af),_ammine_(NR),_methoxy_(OMe),_alkoxy_(OR),_anomeric_(OCO),_aromatic_(Ph),_phenol_(PhOH),_phenoxy_(PhOY,_Y₌_alkyl_or_phenyl)_carboxylic_acid_(COOH), amide(CON),ketone(C O)Catoms;Ar=Ph+PhOH+PhOYC;LH=liphophilictohydrophilicCratio;liphophilicC=Af+Ph+OMe+CON+NR+RO,+PhOY+OCOCatoms; hydrophilicC COOH+PhOH+C OC;relativestandarddeviationsas%ofmeanvalueswerewithin10%ofthereportedmeanvalues.

g_Data_for_precipitated_product_obtained_in_15%_yield_by_acidifying_the_products_purchased_(i.e.,_the_dense_liquid)_at_pH_<_1.5_(see_Section_3.1_).

2.5. Experimentaldesignanddataanalysis

FortheEuphorbiagrowthtrials,asplit-plotexperimentaldesign

withproductasthemainplotandtheirapplicationonplantsas

subplotswasused.Eachoftheﬁvetreatmentsandthecontrolwas

replicatedthreetimes,andeachreplicationconsistedof24potted

plants(72potspertreatment).Collecteddataweresubjectedtoa

two-wayanalysisofvariance(ANOVA)andthetreatmentmeans

werecomparedusingDuncan’sMultipleRangeTest(DMRT)at5%

ofprobabilitybyusingthepackageStatistica(StatsoftInc.,Tulsa,

OK).

3. Results

3.1. ChemicalandphysicalcharacteristicsofSBSandEnersoil

SBSand Enersoil chemical features are reported in Table 1

whereitmaybeobservedthattheproductscontainbothorganic

andmineralmatter.Theformerisconstitutedbyorganic

macro-moleculescontainingaliphaticandaromaticCbondedtoseveral

acidand basicfunctional groups.Theweightaveragemolecular

weight(MW),thenumber averagemolecularweight(MN),and

theMW/MNratioshowthattheSBSarecomposedbya mixof

moleculeswithdifferentmolecularweight.Itisalsolikelythatthe

CtypesandfunctionalgroupslistedinTable1werenot

homo-geneouslydistributedoverthemacromolecularpool.Underthese

circumstances,thedifferentchemicalnatureofthetwoSBSmay

bebetterappreciatedcomparingthealiphatictoaromaticC(Af/Ar)

andthelipophilictohydrophilicC(LH)ratiosreportedinthistable.

BasedonthedeﬁnitionprovidedinTable1footnotes,LHisa

mea-sureoftheproductrelativehydrophilicity,whileAf/Arisameasure

oftherelativealiphatic/aromaticnatureoftheproduct.Thedata

showtheCPorganicmatterismorehydrophilicandmorearomatic

thantheDGone.Themineralfractionoftheproductscontains

sev-eralmainandtraceelements,presumablybondedtotheorganic

functionalgroups.Theorganicandmineralfractionstogether

con-tainallmainplantnutrients.Theproductscompositionwasfound

stableover oneyearstorage.Dataforlongeragingtimearenot

availableyet.Bytheirchemicalfeaturesandwatersolubility,the

SBSareexpectedtoprovideanadequateeasilyavailablepoolof

nutrientsforplantuptake.Thedatashowthat,comparedtoCP,

theDGSBShashigherNcontent,butgenerallylowermineral

con-tent.Bycomparison,Enersoilisadenseliquid,describedbythe

vendor (Intrachem Bio Italia, 2008) asnatural organic

ammen-dantextractedfromLeonarditebyalkalinehydrolysiswithKOH

containing30%drymatter,18%organicmatter(10%beinghumic

matter),0.06%organicN,9%organicC.Asimilarproduct,humic

acidsuppliedbyAdrich,wasreported(Montonerietal.,2009)to

havemolecularweightbetween0.1and105_kDa,_and_to_contain

thesameCtypesandfunctionalgroupsasthoselistedinTable1

fortheCPandDGSBS.ThehumicfractionofEnersoilwas

precipi-tatedatacidpHandwasobtainedin15%yield,thusrepresentinga

substantialportionofthe18%organicmattercontentdeclaredby

thevendor.TheEnersoilhumicfraction,analyzedby

microanaly-sis,yieldedthefollowingw/w%values:67.6C,1.67N,40.6C/N.The

solidstate13_C_NMR_spectra_of_this_product_evidenced_the_same_C

typeandfunctionalgroupsasthoseoftheSBS.Table1showsthat,

comparedtotheDGandCPSBS,theEnersoilhumicmatter

con-tainsrelativelymorearomaticC.ThelowerAf/ArratioforEnersoil

isthelikelyresultsofthelongerdegradationtimeofthepristine

Leonarditeorganicmatter.Theproducthydrophilicity,asmeasured

bytheLHparameter,isinbetweenthevaluesforthetwoSBS.The

lower40.6C/Nratiooftheprecipitatedhumicfractionrelatively

tothe150C/Nratiodeclaredbythevendorforthewholeproduct

suggeststhattheproductcontainsalsononhumicNfreeorganic

matter.

TheEnersoilrecommendeddosebythevendortoapplyvaries

from5to20kgha−1 for soiland fertigationuse, anddilutedto

0.8–1%dry mattercontentfor foliarsprayuse, eachapplication

toberepeatedtwo–threetimesovertheculturegrowthcycle.The

collecteddatashowthattheSBSandEnersoilhadverydifferent

chemicalcomposition.Thelatterhad muchlowerNcontent,as

shownby theC/N ratiobeing150for Enersoil,and 6.5and 7.7

fortheDGandCPSBS,respectively.ThelowerNcontentofhumic

materialextractedfromfossilsource,comparedtoSBS,hasbeen

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Table2

Applieddose(gplant−1₎_of_SBS_and_Enersoil_by_substrate_drench_(sd)_or_foliar_spray_(fs).

Product/applicationmode Assuppliedbythemanufacturera _Dry_matter _C _N

CPSBS/sd 5.0 4.55 1.8 0.24

DGSBS/sd 3.1 3.09 1.3 0.21

DGSBS/fs 1.5 1.54 0.65 0.10

Enersoil/sd 6.2 1.88 0.56 0.0038

Enersoil/fs 3.1 0.94 0.28 0.0019

a_Per_plant_applied_amount_of_Enersoil_dense_liquid_as_purchased_(see_Section_3.1₎_and_of_solid_SBS_as_received_(see_Section_2.1_).

2009).Theaspurchased Enersoildenseliquid wasanalysed for

mineralcontent.ComparedtoDGandCP,itwasfoundtocontain

muchmoreKandNa,andlessFe,Ca,Pandtracemetals(Table1).

Underthesecircumstances,tocomparethethreeproductsfortheir

effectsonEuphorbiaxlomiplants,theEnersoilwasappliedatthe

doserecommendedbythevendor.TheSBSwereappliedatthe

nearlyequaldoseoftheaspurchasedEnersoildenseliquid.This

choicewasmadebasedonthefactthat,commercially,materials

areevaluatedfortheirbeneﬁtsrelativelytothecostperkgofthe

aspurchasedmaterial.Table2reportstheapplieddosesofthethree

products.Duetotheintenseblackcolor,theCPSBSwasappliedonly

assubstratedrench;infact,foliarsprayapplicationofthisproduct

causedformationofbrownspotsonleaveswhichwereexpectedto

reduceplantphotosyntheticactivity(MoralesandWarren,2012).

ThiseffectwasobservedalsobyapplyingthesameCPSBSdoseas

theDGSBSone.Thelatterproductwaslesscoloredanddidnot

presentthesamephenomenonastheformerone.Thedoses

cho-senforcomparingthedifferentmaterialsinvestigatedinthework

werebasedonthefollowingcriteria.First,fromthecommercial

pointofviewproductsareratedbasedontheirbeneﬁt/costratio,

wherecostisreferredtotheweightoftheproductassuppliedby

thevendor.Duetothedifferentcompositionoftheinvestigated

products,thedoseswereworkedouttoperformtwokindsof

com-parison:(i)tocomparetheSBSwithEnersoiland(ii)tocompare

thetwoSBS,onewiththeother.Thus,asEnersoilisthereference

commercialmaterial,thisproductwasappliedatthedoses

recom-mendedbythevendor.Table2showsthatforthesubstratedrench

(sd)application,weused6.2goftheaspurchasedEnersoildense

liquidversus5.0gofthesolidCPassuppliedbythemanufacturer

(seeSection2.1).ThisallowedthecomparisonoftheCPSBSversus

Enersoilatclosedoses.ForcomparingthetwoSBS,onewiththe

other,weusedthecriterionofcomparingthematthesameapplied

Ndoses.Itmaybeobservedthatwhilethedrymatterdosesrange

from0.94to4.55gplant−1,thedifferencesintheCandNapplied

dosesbythedifferenttreatmentsvaryoverawiderrange.

Rela-tivelytothelowestdose,thehighestapplieddosewas4.6×higher

fordrymatter,6.4×higherforCand126higherforN.TheCPand

DGsubstratedrenchappliedNdoseshappenedtobeequal.

3.2. Plantgrowthandbiomassyield

Table3reportstheplantbiometricdataasaffectedbythe

dif-ferenttreatmentscomparedtothecontrolplants.Nosigniﬁcant

differenceswererecordedforplantheightbythedifferent

treat-mentscomparedtothecontrolasanaveragevalueof15.7cmwas

recordedirrespectiveofthetreatment.Theothergrowth

param-eters were all affectedby the treatments. The highest number

ofleaveswasmeasuredintheplantsgrowninthepotstreated

withCPby substratedrench (63.3leavesplant−1), followed by

those treated withDG by foliar spray and Enersoil by drench,

i.e.,52.8 and 52.0 leavesplant−1,respectively. The lowest

pro-ductionwasobserved(Table3)inthecontrolplants(32.5leaves

plant−1)(Table3).Leafareawashighestinthesametreatments

characterizedbythehighestleafnumberproduction;itwas686.3,

654.8and630.3cm2_for_CP_by_substrate_drench,_DG_by_foliar_spray

and Enersoil bydrench, respectively, and lowestin thecontrol

(386.0cm2_)._Flowers_production_was_deﬁnitely_highest_in_the_plants

growninthepotstreatedwithCPbysubstratedrench(4.0

ﬂow-ersplant−1);thelowestproductionwasobservedinthecontrol

plants(1.2ﬂowersplant−1);theremainingtreatmentsgavehigher

ﬂowerproductionthanthecontrolplants,butlowerproduction

thanCP(Table3).Shoottorootratio(S/R)washighestinplants

treatedwithCPappliedbysubstratedrench(12.3);alowervalue

wasmeasuredfortheDGsubstratedrenchtreatment(8.2);the

con-trolandtheothertreatmentsgavethelowestvalues.Moreover,a

signiﬁcant(p≤0.05)interaction“productxapplicationmode”was

evidencedforS/R(Table3).Overall,theCPsubstratedrench

treat-mentgavethehighestvaluesfornumberofleavesperplant,leaf

area,ﬂowerproductionperplant,andS/R.Themeasuredvaluesfor

theseparameterswere2–3timeshigherthanthevaluesmeasured

forthecontrolplants.Theeffectsoftheothertreatmentsrankedin

betweentheCPsubstratedrenchtreatmentandthecontrol.

Fig.1reportsthebiomassproductionpartitionovertheplant

stem,leavesandroot.Totalbiomassproductionwassigniﬁcantly

affectedbythetreatmenttypologyashighertotaldryweightwas

measuredinEuphorbiaxlomiplantstreatedwithCPbysubstrate

drench (28.0g), with respect to the other treatments (average

14.1g).Thelowesttotaldryweightwasrecordedforthecontrol

plants(6.5g).TheCPtreatmentthereforeenhancedbiomass

pro-ductionbya2×factorrelativelytotheothertreatmentandbya

4×factorrelativelytothecontrol.Thisdifferencewasessentially

causedbythehigherdryweightofleavesoftheplantstreatedwith

CPappliedbydrench(17.7g)relativelytotheothertreatments

(average7.8g)andthecontrol(3.8g).Biomasspartitioningover

theotherplantorgansshowedlowerdifferencesbetweenCPby

drenchandtheothertreatments:i.e.,forstems4.2gbyCPversus

2.5gbytheothertreatments,forrootdryweight6.1gbyCPversus

3.9gbytheothertreatments,whilethecontrolplantsalways

evi-dencedthelowestvalues,1.8and0.9gforstemandrootdryweight,

respectively(Fig.1).

Fig.2reportstheplantsRelativeGrowthRate(RGR)forthe

con-trolandthedifferenttreatmentsover thecultivationperiod,in

August–October2013.Nosigniﬁcantdifferenceswereobservedin

August.InSeptember,thetreatmentsgavehigherRGRcomparedto

thecontrol(p≤0.05),withtheCPtreatmentwascharacterizedby

thehighestvalue.InOctober,thegreatereffectbytheCPtreatment

wasevenmoreevident(p≤0.01).TheRGRof3.3gg−1d−1bythe

CPtreatmentattheendofthecultivationperiodinOctoberwas

signiﬁcantlyhigherby1.3×factorthantheaveragevalueforthe

othertreatmentsandby1.8×factorthanthelowest1.8gg−1d−1

RGRrecordedforthecontrolplants(Fig.2).

Fig.3reportstheWaterUseEfﬁciency(WUE)fortheEuphorbias

growninthetreatedpotsversusthecontrolplants.Itshowsthat

theCPtreatmentgavethehighest1.3gL−1WUEvalue,followedby

thosefortheothertreatmentsrunningfrom0.55to0.75gL−1and

bythelowest0.3gL−1valueforthecontrolplants.

3.3. LeafSPADindex,colorandgasexchanges

Tables 4 and 5 report the data related to the plant

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Table3

Effectofproduct(P)andapplicationmode(A)onplantheight,leavesproduction,leafarea,ﬂowersproductionandshoot/rootratio(S/R)ofEuphorbiaxlomipottedplants.

Product/applicationmode Plantheight(cm) Leaves(n.plant−1) Leafarea(cm2₎ _Flowers_(n._plant−1₎ _S/R

Enersoil/fs 15.2a_a _54.2_ab _562.8_b _1.8_bc _1.9_c Enersoil/sd 16.1a 52.0ab 630.3ab 2.4b 2.7c DGSBS/fs 16.4a 52.8ab 654.8a 1.7bc 1.6c DGSBS/sd 16.3a 47.2b 544.4b 2.6b 8.2b CPSBS/sd 16.5a 63.3a 686.3a 4.0a 12.3a Control 13.9a 32.5c 386.0c 1.2c 4.0c Signiﬁcance Product ns * * * * Applicationmode ns ns * * * PxA ns ns ns ns *

*:signiﬁcant;ns:notsigniﬁcant.

a_For_each_column,_means_followed_by_different_letters_are_{signiﬁcantly}_different_at_p_≤_0.05_(DMR_test).

Fig.1.EffectofproductandapplicationmodeondrybiomassproductionofEuphorbiaxlomipottedplantsmeasuredforeachplantorgan:i.e.,stem,leavesandroots.Values aremeans±standarderror.Foreachcolor,columnswithdifferentlettersindicatesigniﬁcantlydifferentvaluesatP≤0.05(DMRtest).

Fig.2.EffectofproductandapplicationmodeonRelativeGrowthRate(RGR,gg−1_day−1₎_of_Euphorbia_x_lomi_potted_plants_measured_in_August,_September_and_October 2013duringtheplantgrowthandproductionperiod.Valuesaremeans±standarderror;ns,*,**indicatenon-significantorsignificantdifferentvaluesatP≤0.05and0.01, respectively(DMRtest).Significantdifferencesareasfollows:inSeptember,p<0.05betweenthefivetreatmentsandthecontrol;inOctober,p<0.01CPbetweenSBS/sdand thecontrol,p<0.05betweenCPSBS/sdandtheotherfourtreatments,p<0.05betweentheotherfourlattertreatmentsandthecontrol.

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Fig.3.EffectofproductandapplicationmodeonWaterUseEfﬁciency(WUE,gL−1₎_of_Euphorbia_x_lomi_potted_plants._Means_are_values_±_standard_error._Columns_with differentlettersindicatesigniﬁcantlydifferentvaluesatP≤0.05(DMRtest).

Table4

Effectofproduct(P)andapplicationmode(A)onleafchlorophyllcontent(SPADindex)andcolorcoordinates(CL,CAandCB)ofEuphorbiaxlomipottedplants.

Product/applicationmode Chlorophyllcontent (SPAD) Colorcoordinates CL CA CB Enersoil/fs 35.7a_b _37.4_bc _−14.4_bc _20.5_ab Enersoil/sd 35.6b 37.0bc −14.0bc 19.7ab DGSBS/fs 39.6ab 40.1b −16.5ab 24.0a DGSBS/sd 36.0b 39.0b −15.6ab 20.3ab CPSBS/sd 42.0a 32.4c −19.9a 26.4a Control 31.6c 47.2a −11.1c 17.6b Signiﬁcance Product * * * * Applicationmode ns ns ns ns P×A ns ns ns ns

a_For_each_column,_means_followed_by_different_letters_are_{signiﬁcantly}_different_at_p_≤_0.05_(DMR_test).

Table5

Effectofproduct(P)andapplicationmode(A)onleafgasexchanges–net assimila-tionCO2(ACO2)andstomatalconductance(gs)–ofEuphorbiaxlomipottedplants.

Product/applicationmode ACO2(␮molCO2m−2s−1) gs(mmolm−2s−1)

Enersoil/fs 2.74a_d _0.010_cd Enersoil/sd 3.45c 0.014c DGSBS/fs 4.54b 0.023bc DGSBS/sd 5.28b 0.031b CPSBS/sd 6.19a 0.043a Control 1.73e 0.005d Signiﬁcance Product * * Applicationmode * * P×A ns *

a_For_each_column,_means_followed_by_different_letters_are_{signiﬁcantly}_different atp≤0.05(DMRtest).

chlorophyllcontentwashighestintheplantsgrowninthepots

treated with CP by drench (42.0), followed by DG by spray

(39.6),by theother treatments yielding values around 36, and

the signiﬁcantly lowest value of 31.6 for the control plant.

Table4alsoreportsthevaluesfor thethree CIELABcolor

coor-dinates, namelythe lightness (CL),the red/green (CA) and the

yellow/blue(CB)coordinate(Datacolor,2008).Inthissystem,lower

CL indicatesless transparent color, more positive CA indicates

increasing redness, and more negative CA indicates increasing

greeness,morepositive CBindicatesincreasingyellowness,and

more negativeCBindicatesincreasingblueness. Thedata show

that theleaves of theplants treated with CP have the lowest

CL, themost negative CA and the mostpositive CB, while the

opposite is true for the control plant leaves. These differences

in the color coordinates of CP and control leaves correspond

to more intense green color in the former perceived by the

eyeand, consequently,toa higherornamentaland commercial

value.

Table 5 shows the remarkably highest leaf gas exchanges

of the plants grown in the pots treated by CP substrate

drench. The net assimilationCO2 (ACO2)value for these plants

was6.19␮molm−2s−1,followed bythesigniﬁcantly lower

val-ues of the plants treated by DG substrate drench and DG

foliar spray, 5.28 and 4.54␮mol CO2m−2s−1, respectively, by

the plants treated with Enersoil by substrate drench (3.45),

by the plants treated with Enersoil by foliar spray (2.74),

and by the lowest 1.73 value for the control plants. A

sim-ilar ranking order is observed for the stomatal conductance

(gs) as higher value was recorded in Euphorbias treated with

CP by drench and lower gs was measured with Enersoil

treatments and in the control plants (Table 5); a signiﬁcant

(p≤0.05)interaction“product×applicationmode”wasalso

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Table6

Rankinga_of_treatmentsb_in_order_of_{signiﬁcantly}_decreasing_effect_on_the_different_plant_performance_indicators.

Plantperformanceindicator Rankingorder Enhancementfactorc

CP/control CP/Enersoil

Plantheight (Table3) CP/sd=DG/sd=DG/fs=Enersoil/sd=Enersoil/fs=control 1.2ns 1.0ns

Leavesperplant(Table3) CP/sd≥DG/fs=Enersoil/sd=Enersoil/fs3_DG/sd>_control _1.9 _1.1_ns

Leafarea(Table3) CP/sd≥DG/fs=Enersoil/sd3_Enersoil/fs₌_DG/sd>_control _1.7 _1.0_ns

Flowerperplant(Table3) CP/sd>DG/sd=Enersoil/sd3_Enersoil/fs₌_DG/fs3_control _3.3 _1.7

S/R(Table3) CP/sd>DG/sd>Enersoil/sd=Enersoil/fs=DG/fs=control 3.1 4.5

Biomassproduction(Fig.1) CP/sd>DG/sd=Enersoil/sd=Enersoil/fs=DG/fs>control 4.0 2.0

RGR(Fig.2) CP/sd>DG/fs=Enersoil/sd>Enersoil/fs=DG/sd>control 1.8 1.2

WUE(Fig.3) CP/sd>DG/fs=Enersoil/sd3_Enersoil/fs₌_DG/sd3_control _4.3 _1.6

Chlorophyllcontent(Table4) CP/sd=DG/fs3_DG/sd₌_Enersoil/fs₌_Enersoil/sd_>_control _1.3 _1.2

CL(Table4) CP/sd=Enersoil/fs=Enersoil/sd3_DG/fs₌_DG/sd_>_control _0.69d _0.88_ns CA(Table4) CP/sd=DG/fs=DG/sd3_Enersoil/fs₌_Enersoil/sd3_control _1.8 _1.4 CB(Table4) CP/sd=DG/fs=DG/sd=Enersoil/fs=Enersoil/sd3_control _1.5 _1.3_ns ACO2(Table5) CP/sd>DG/sd>DG/fs>Enersoil/sd>Enersoil/fs>control 3.6 1.8 gs(Table5) CP/sd>DG/sd3DG/fs>Enersoil/sd=Enersoil/fs3control 8.6 3.1 a_When_there_are_no_signiﬁcant_differences_between_treatment_the_“=”_sign_is_used._The_“≥”_symbol_is_used_when_the_adjacent_treatments_in_the_ranking_do_not_differ, buttheydifferwiththosepreviouslypositionedintheranking.Forexample,CPsd=DGfs=Enersoilsd=Enersoilfs≥DGsd>controlmeansthatthereisnostatisticaldifference amongCPsd,DGfs,EnersoilsdandEnersoilfs,thatDGsdisstatisticallyequaltoEnersoilfs,butitissigniﬁcantlylowerthanCPsd,DGfsandEnersoilsd,andthatthecontrolisthe lowest.

b _CP

sd=treatment with CPSBSby substrate drench;DGsd and DGfs=treatmentwith DGSBS by substrate drench and foliar spray, respectively;Enersoilsd and Enersoilfs=treatmentwithEnersoilbysubstratedrenchandfoliarspray,respectively.

c _CP/control_value_ratio_and_CP/Enersoil_best_value_ratio;_ns₌_not_{signiﬁcant.} d _Lower_value_indicates_relatively_higher_color_darkness.

Table6summarizestherankingofthedifferenttreatmentsin

orderof decreasingeffectoneach plantperformanceindicator,

basedontheresultsreportedinTables3–5andFigs.1–3.

4. Discussion

Itmaybeobservedthatthereisnodeﬁnitedifferenceofeffects

ascausedbyfoliarsprayorsubstrateapplicationmode.Onmost

plantindicatorsthedifferentapplication modesyield thesame

effect.Thelargestmajorityofeffectdifferencesarisefromthe

dif-ferenttypesofappliedproducts.TheCPsubstratedrenchtreatment

ranksﬁrstinallcases.Forsevenplantperformanceindicatorsit

yieldsthehighestenhancement,sharingtheﬁrstrankingposition

withnoothertreatment.Theenhancementfactorisreportedin

Table6astheratiooftheindicatorvaluebytheCPtreatmentto

thevaluerecordedforthecontrolplants.Itmaybeobservedthat

thisfactorrangesfrom1.3fortheChlorophyllcontentindicator

to8.6forthestomatalconductance(gs)indicator.Particularlyhigh

aretheenhancementfactorvaluesforthewateruseefﬁciency(4.3),

biomassproduction(4.0),netassimilationCO2(3.6),andtheﬂower

production(3.3).ThedatareportedinTable6pointoutthatall

indi-cators,particularlytheplantﬂowerandbiomassproductivity,are

wellrelatedtotheplantphotosyntheticactivityasmeasuredbythe

ACO2parameter.ThenetassimilationCO2isshowntobethemost

sensitiveparametertowardthedifferenttreatments.This

indica-tordeterminesthehighestselectivityintherankingorderbased

onstatisticalsigniﬁcance;i.e.,therearenotwotreatments

yield-ingthesameeffect.Theﬁrsttwointherankingorderfortheeffect

onACO2aretheCPandtheDGsubstratedrenchtreatments.These

sametreatmentsrankalsoﬁrstandsecondfortheireffectonthegs

parameter.InthisworkthenetassimilationCO2isnicelyrelated

tothestomatalconductancebythefollowingequation:

ACO2=a+bgs (1)

where a=1.58±0.27, b=115±10.8, R (correlation

coefﬁ-cient)=0.98.Theotherindicatorsarerelatedtothenetassimilation

CO2 byasimilarlinearrelationship,althoughwitha lower

cor-relationcoefﬁcientrangingfrom0.70to0.78over allmeasured

indicators.Thedatashowthattheimportanceofenhancingthe

plantphotosyntheticactivitytoenhanceinturnplantgrowthand

productivity.

LookingforapossiblereasonoftherankingorderinTable6,

onecouldobservethatseveralelementscanbethecauseofthe

remarkablehighesteffectsofCP.Thesemaybethehighest

sup-pliedNperplantamount(Table2),aswellasthehighestcontent

ofsomemineralelementssuchasFe,CaandP,andofcarboxylic,

phenolicandaminogroups,asshowninTable1.These

functionali-tiesarelikelytocomplexmineralions,suchFeionsknowntohave

animportantroleintheplantphotosyntheticactivity.Indeed,it

maybeobservedfromTable1thatthesumoftheNR,PhOHand

COOHgroupsconcentrationvalues,expressedasmolefractionof

totalorganicCmoles,decreasesfrom0.23forCPto0.19forDG,

andfurtherto0.09for Enersoil.Thecapacity ofSBStokeepFe

ionsinsolutionatcircumneutralpHbyitscomplexingacidand

basicfunctionalgroupshasbeenpreviouslyinferredresponsible

forthephotosensitizingpropertiesofSBS.Aspreviouslyreported,

bytheseproperties,theSBSarecapabletopromotethe

mineraliza-tionoforganicpollutants(Avettaetal.,2013;Gomisetal.,2014),

andarealsothelikelycauseoftheenhancedphotosyntheticactivity

observedinhorticultureplants(Sortinoetal.,2014).

TheavailabilityofFeions,andotherelementssuchasN,K,Ca,

Mn,Zn, forenhancingtheplantphotosyntheticactivity,andthe

leafchlorophyllcontentandcolor(Nettoetal.,2005;Dordasand

Sioulas,2008)hasbeenclaimedbyseveralauthorsusing

commer-cialandnoncommercialproductsinthecultivationofseveralplant

species,suchastomato(SánchezSánchezetal.,2009Siminisetal.,

1998),onionseedlings(Bettonietal.,2014),cowpea(Nerietal.,

2002a),andchrysanthemumplants(Fanetal.,2014).Otherauthors

havereporteddatashowingthecloserelationshipbetweenleaf

chlorophyllcontent,andplantgrowthandyield(Enriquezetal.,

2004;Cigandaetal.,2009).Severalothershavereportedenhanced

plantgrowthand productivity,and/orphotosynthesis,by

appli-cationof commercialandnon commercialhumic substancesto

thegrowingsubstrateforthecultivationoftomatoplants(ThiLua

andBöhme,2001),pepper(Aranconetal.,2006),grapevine

root-stocks(Zachariakisetal.,2001),olivetrees(Tattinietal.,1990),and

ornamentalplants(Ahmadetal.,2013;Costaetal.,2008)aswell

asthroughfoliarspray(Fernández-Escobaretal.,1999Nerietal.,

2002b),withhighereffectivenessofsubstratedrenching(Böhme, 1999Paunovi ´cetal.,2013).Theeffectivenessoftheseproductson

improvingplantgrowthalsodependsonthehumateformandon

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concentrationandfrequencyoftreatments,astheyareableto

stim-ulaterootgrowthinamannersimilartoauxin.Itisalsosuggested

thattheseproductsmayup-regulate genesresponsibletoplant

organogenesisandﬂowerdevelopment.

WhereasthereasonoftheobservedeffectsbySBSontheplant

photosyntheticactivityis certainly matterof scientiﬁc interest,

fromthecommercialpointofviewtheplantgrowthand

produc-tivityimpactdirectlytheeconomyoftheplantproductionprocess

andmarketvalue.Atthisregard,thewateruseefﬁciency(WUE)

hasbothenvironmentalandeconomicrelevance.Themanagement

ofwaterresourceshasbecomeakeyissueinmany

governmen-talpolicies.Basically,ithasbecomeclearthatitis necessaryto

manageallformsofwaterusewithgreaterprecisionand,in

partic-ular,tomanageunmeasuredusesofwaterincludingtheimpactsof

plantationforestry,smallfarmdams,thecaptureofoverlandﬂows,

reductionsinreturnﬂowsasaresultofincreasesinirrigation

efﬁ-ciencyandsalinityinterception(Young,2010).TheWUEissueis

especiallyimportantinagriculture,asthissectorofhuman

activ-itiesisthemajoruserofwater,accountingforabout70%ofthe

world’sfreshwaterwithdrawalsandover40%oftheOrganisation

forEconomic Co-OperationandDevelopment (OECD)countries’

total waterwithdrawals (Parris, 2010).The adoptionof

fertiga-tionasusedinthis workiscertainly inlinewithcurrentwater

savingstechnologiesandpractices.However,theuseofefﬁcient

plantgrowthbiobasedauxiliaries,suchasCP, allowsadditional

watersavings.TheWUEenhancementbroughtaboutbythe

treat-mentsinthis work,relativelytothecontrol,couldbedue toa

physiologicalprocessassuggestedbyMorardetal.(2010).Inthis

process,thehighmolecularsizefractionsoftheappliedproducts

couldparticipateinplantwatersavingbyslowingdownits

pas-sageinroots.However,inthepresentwork,CPhasrankedﬁrstfor

itshighesteffectsonWUE,biomassandﬂowerperplant

produc-tion,S/R,RGR,ACO2andgs,withnoothertreatmentmatchingits

performance.TheWUEvaluebytheCPtreatedplantsiscertainly

connectedtothehighestbiomassproduction(Fig.2).Inturn,the

enhancementofbiomassandﬂowerperplantproductionaremost

likelytheresultsoftheremarkableplantphotosyntheticactivity

enhancementcausedbyCP.Theserelationshipsstronglypointout

howsubstancescapabletoenhancetheplantphotosynthetic

activ-itycangeneratepracticalrelevanteconomicand environmental

beneﬁtsforagricultureandsociety.Basedontheabovecited

lit-erature,itispossibletoobservethatthesametypesofbeneﬁts

canbeobtainedbyusinghumicsubstances.Asidefromthefact

thatthisworkshowsmuchbetterperformanceofSBScomparedto

thecommercialEnersoilhumicmaterialsourcedfromleonardite,

thecomparisonof SBSandhumic substancescomingfrom

fos-silsourcesshouldaccountalsoforthesourceviability.TheSBS

areobtainedfrommunicipalbiowastes;thismaterialisthe

easi-estworldwidemostavailablesourceofrenewableorganicmatter.

Duetomunicipalcollection,itisfoundinconﬁnedspaces,

practi-callyfreeofchargeforpotentialusers.Forthisreason,municipal

biowastehasbeendeﬁnedanegativecostsourceoforganic

mat-ter(Sheldon-Coulson,2011).Ifproperlyexploitedbyprocessingit

toaddedvalueproducts,itwouldbecomeaviablebiobased

feed-stock.Underthesecircumstances,theuseoftheSBSinagriculture,

aswellasinthechemicalindustry,wouldallowseveraleconomic

andenvironmentalbeneﬁtsindifferentsectorsofhumanactivities.

Thereplacementofhumicsubstancesandsyntheticchemicalsin

theagricultureandchemicalmarketwouldallowsavingsoffossil

sourcesofhumicsubstances,carbonandoil,andtheconsequent

decreaseoftheemissionofgreenhousegases.

InordertoevaluatethepotentialmarketabilityoftheSBS,one

shouldconsiderthatproductsmarketabilityisratedbasedon

ben-eﬁtstocostratio,wherecostsarereferred totheweightofthe

productasmarketedbythevendor.Formthispointofview,the

perplantappliedamountsofthesolidSBSproductsarelowerthan

thoseoftheaspurchasedEnersoildenseliquid(Table2).Yet,the

effectsoftheSBSarehigher.ThisallowtoforecastthattheSBS

couldbeallocatedinthemarketatthesamepriceperkgasEnersoil

andbemorecompetitivefortheirperformanceperkgofapplied

productasmarketed.TheresultsalsoshowthattheCPSBSapplied

bysubstratedrenchismoreeffectivethantheDGSBSappliedby

substratedrench,althoughtheamountofappliedNisthesamein

bothcases.TheresultsthereforeallowtoconcludethatbothSBS

aremoreeffectivethanEnersoil,whencomparedfortheratio

bene-ﬁt/amountofappliedproductasreceivedbythevendororsupplied

bythemanufacturer,andthattheCPSBSismoreeffectivethanthe

DGSBSatequalNapplieddoses.Thevis-à-visperformance

compar-isonofSBSwiththecommercialEnersoilproductreportedinthis

workdemonstratesthatSBScouldefﬁcientlyreplacecommercial

humicproductsintheagriculturemarket.Thecurrentmarketvalue

oftheseproductsrangesfrom1.5to3.5-- kgC −1₍_Ebay,_2015;_Alibaba,

2015)forthesolidproduct,andisevenhigherforliquidproducts.

TheEnersoilproductcanbepurchasedin1kgpackagefor-- 7C kg−1

(Viscardi,2015).Basedonthe30%drymattercontent,thispriceis

equivalenttoover23-- kgC −1_dry_matter._The_SBS_production_cost

hasbeenestimatedabout0.1–0.5-- kgC −1₍_Montoneri_et_al.,₂₀₁₁_).

Theﬁguresprospectacosteffectiveproductionandsuccessful

allo-cationofSBSintheorganicfertilizermarket.Toappreciatethefull

potentialofSBSusesinagriculture,itshouldbetakenin

considera-tiontherecentworkpublishedbyFranzosoetal.(2015a,b,c).These

authorshavedemonstratedthatSBSreactedwith

polyethylene-co-polymersyieldcompositesthatcanbemanufacturedasmulch

ﬁlmswithenhancedmechanicalstrength.Theseﬁndingsofferthe

intriguingperspectivethatthesameﬁlmscouldperformtwo

func-tions,i.e.,toprovideprotectionforcrops,andattheendoftheir

productlifetoperformasauxiliariesforplantgrowthby

releas-ingSBStothesoil.ThemultipurposevalueoftheSBSprospectsa

scenariowherecurrentmunicipalbiowastetreatmentplants

inte-gratedwithSBSproductionfacilitywereturnedintocost-effective

bio-reﬁneriesmanufacturingaddedvalueproductsforuseinother

industrialsectors.Inthisfashionablescenario,anewsustainable

businessmodel couldbegenerated.Based ontheconversionof

biowastestobio-basedproductandviceversa,thisbusinessmodel

couldmoresafelyoperateintotheeco-systems.

Itisobviousthatthepresentmanuscriptdoesnotreport

exhaus-tiveresultstoanswerallthemanyquestionsthatcanbeposed

aboutdosesandreasonsforthedifferenteffectswhichhavebeen

observed.However,itoffersscopeforfurtherexperimentalplan

aimedtocomparethematerialsatthesameCandNapplieddoses.

Theauthorsfeelthatsuchfurtherinvestigationwouldhavemore

valueforitspotentialtoassessthemodeofactionofthedifferent

materials and understand the reasons for the different

perfor-mances. Nevertheless,thepresent resultshave valuesincethey

allowtheevaluationoftheSBSpotentialmarketabilitythroughthe

comparisonwiththecommercialEnersoilproduct.Thisismostly

importantforpotentialprocess/productusersinordertodecide

undertakingtheriskofscalingupSBSproductionatcommercial

level.Inthisrespect,themanuscriptshouldbeappraisedforthereal

environmentalandeconomicperspectivesofferedbythereported

resultsforagriculture,themanagementofurbanwastes,andthe

chemicalindustry.

5. Conclusion

The SBS, obtained by the alkaline hydrolysis of municipal

biowastecompostanddigestate,particularlytheCPSBO,havebeen

proventoenhancethephotosyntheticactivity,thenumberof

ﬂow-ersperplant,theshoottorootratio,thebiomassproduction,the

relativegrowthrate,aestheticvalue,andwaterefﬁciencyuseof

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Leonardite-basedproduct,relativelytocontrolplants.Theresults

conﬁrmpreviousworksperformedwiththesameSBSon

horticul-tureplants.Theyprospectacosteffectiveproductionandsuccessful

allocationofSBSintheorganicfertilizermarket.

Acknowledgement

ThisworkwascarriedoutpartlywithfundsfromtheItalian

MinistryofAgricultureaspartofthe“Agrienergia”project.

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