Tomato Productivity and Quality in Aquaponics

21 Pages·2016·4.44 MB·English

water
Article
Tomato Productivity and Quality in Aquaponics:
Comparison of Three Hydroponic Methods
ZalaSchmautz1,*,FionnaLoeu2,FrankLiebisch2,AndreasGraber1,AlexMathis1,
TjašaGriesslerBulc3andRankaJunge1,*
1 InstituteofNaturalResourceSciences,ZurichUniversityofAppliedSciences,Grüental,8820Wädenswil,
Switzerland;fi[email protected](A.G.);[email protected](A.M.)
2 InstituteofAgriculturalSciences,ETHZurich,Universitätsstrasse2,8092Zurich,Switzerland;
fi[email protected](F.L.);[email protected](F.L.)
3 FacultyofHealthSciences,UniversityofLjubljana,Zdravstvenapot5,1000Ljubljana,Slovenia;
[email protected]
* Correspondence:[email protected](Z.S.);[email protected](R.J.);
Tel.:[phone](Z.S.);[phone](R.J.)
AcademicEditor:M.HaïssamJijakli
Received:14September2016;Accepted:9November2016;Published:16November2016
Abstract: Aquaponics (AP) is a food production system that combines hydroponic (HP) crop
productionwithrecirculatingaquaculture. Differenttypesofhydroponicsystemshavebeenused
forgrowingcropsinaquaponics. However,veryfewstudieshavecomparedtheirsuitabilityand
efficiencyinanaquaponiccontext. Thestudypresentedherecomparestomatoyield,morphological
(external)andbiochemical(internal)fruitquality,andoveralltomatoplantvitalityfromthreedifferent
HPsystems(nutrientfilmtechnique,dripirrigationsystem,andfloatingraftculture)andexamines
thedistributionofnutrientsindifferentpartsofthetomatoplant. ThreereplicateAPsystemswere
set up, each incorporating the three different HP systems coupled with a separate recirculating
aquacultureunitgrowingNiletilapia. Theresultsshowedthatthechoiceofthecultivationsystem
hadlittleinfluenceonmostoftheabove-mentionedproperties. Tomatofruitmineralcontentwas
foundtobeinsimilarrangeforN,P,K,Ca,Mg,Fe,andZnasreportedintheliterature. Yieldand
fruit quality were similar in all three systems. However, the drip irrigation system did perform
slightlybetter. Theslightlyhigheroxygenradicalabsorbancecapacity(ORAC)ofthefruitsgrownin
APincomparisontocommerciallyproducedandsupermarketderivedtomatoesmightindicatea
potentialforproducingfruitswithhigherhealthvalueforhumans.
Keywords: aquaponics;hydroponics;dripirrigation;floatingraftculture;nutrientfilmtechnique;
tomato;tilapia
1. Introduction
Duetotheincreasingdemandforfoodandtheneedtosavefreshwater,foodproductionefficiency
must be increased. Currently, more than 70% of the world’s freshwater resources are used for
agriculturalpurposes[1], increasingtheneedforimprovedwateruseefficiencyandtherecycling
of water in semi- or closed production systems. Food provision has a significant impact on the
environment through greenhouse gas emissions, depletion of phosphorus, use of land and water
resources,andreleaseofchemicalproducts[2]. Ontheotherhand,todaymorethan54%oftheworld’s
populationlivesinurbanareas. Itisexpectedthattheurbanizationtrendwillincreaseto66%ofthe
globalpopulationby2050[3].
Urbanagriculturecanproducefoodlocally,usesresourcesveryefficientlyandhasaminimum
negativeimpactontheenvironment[4]. Foodproducersnotonlyfacethechallengeofsupplying
Water2016,8,533;doi:10.3390/w8110533 www.mdpi.com/journal/water
Water2016,8,533 2of21
staplefoodstomeetcaloricdemand,butalsothechallengeofproducingawidevarietyofhighquality
foodswithgoodnutritionalproperties. Therefore,itisimportanttofindsustainablefoodproduction
systemswhichcanalsobemaintainedwithinsettlementsorcities.
Aquaponics (AP) is one of the most promising sustainable systems for food production that
combineshydroponicsystems(HP)withrecirculatingaquaculturesystems(RAS).Ithasthepotential
to play a major role in food provision and tackling global challenges such as water scarcity, food
security,waterpollution,highenergyuseandexcessivefoodtransportmiles[5]. IfAPisoperatedin
aclosedwaterloop,ithaslittleenvironmentalimpactbecausethefoodisproducedwithlowwater
consumption [6,7]. Plant production yields in AP have been reported to be higher than for crops
grown in soil [8,9], however data are scarce. In AP, nutrients enter the system in the form of fish
feed. Thefeedisingestedandmetabolizedbythefish. Theremainsofthefeedandthemetabolic
productsfromthefishdissolveinthewatercreatinganaquacultureeffluentthatprovidesmostof
thenutrientsrequiredforplantgrowthinaHPpartofthesystem. Microorganismsinthebiofilter,on
plantroots,andintherecirculatingwaterreleaseandconvertthenutrients(e.g.,phosphatesfromthe
debris,andammoniumtonitrate)andtheplantsassimilatethem,thustreatingthewater,whichflows
backtotheaquaculturecomponentofthesystem[5,8]. InAP,fish,plants,andbacteriacoexistinthe
samewater,albeitindifferentcompartmentsofthesystem[10]. DifferenttypesofHPsystemshave
beenusedforgrowingcropsinAP:(i)dripirrigation;(ii)floatingraftculture;(iii)gravelbed;and
(iv)nutrientfilmtechnique(NFT)[5–8,11–14],howeververyfewstudieshavecompareddifferentHP
productionsystemsinanAPcontext. TheonlypaperweareawareofisbyLennardandLeonard[15]
comparesfloatingrafts,gravelbeds,andNFTforgrowinglettuceinAPandfoundthatNFTproduced
significantlylessbiomassandremovedthenutrientsfromfishwaterlessefficientlythantheother
twosystems.
Generally, all plant species that can be adapted to growth in HP systems can also be grown
inAP[16], meaningthereisanextremelywidevarietyofchoices. Savidov[17]reportedgrowing
over 60 different types of plant species in AP. Lettuce, specialty greens and herbs (chives, basil,
spinach, and watercress) have low to medium nutritional requirements and are well adapted to
AP[16]. Fruityieldingplants(tomato,bellpepper,cucumber,andsquash)haveahighernutritional
demandandperformbetterinheavilystockedAPsystems. Inindoorsystems,themostcommonly
used tomatoes are greenhouse varieties which are better adapted than field cultivars to low light
andhighhumidityconditions[16]. AccordingtoFAOstat[18],tomatoesareworldwidethesecond
most important vegetable crop after potatoes. Tomatoes are rich in nutrients and vitamins which
are associated with healthy food, i.e., carotenoids, flavonoids and lycopene [19,20]. Leaf nutrient
concentrationscanbeusedtodetectthemineralnutritionalstatusoftheplantsandthusmighthelpto
revealdifferencesinnutrientavailabilityindifferentgrowingsystems,whereasfruitnutrientcontent
indicates the nutritional value for human consumption [21]. Graber and Junge [5] compared four
varietiesoftomatoes(Grapella,RoseofBerne,FrogKingGoldenOrb,andSweetfromHungary)in
AP,andincommercialHPcultivationwithapplicationsofmineralfertilizeraccordingtoResh[22].
TheyfoundthatallvarietiesperformedbetterinAP.
Thepurposeofthisstudywastocomparetomatoyields,morphological(external)andbiochemical
(internal)quality,andoverallplantvitalityinthreedifferentHPsystems(NFTsystem,dripirrigation
system, andfloatingraftculture). Inaddition, nutrientuptakeanddistributionwithinthetomato
plantswasalsotobedetermined.
2. MaterialandMethods
Theexperimentwasconductedfrom31Marchto5November2014(220days)inadoubleplastic
coveredgreenhouseattheZurichUniversityofAppliedSciences(ZHAW)inWädenswil,Switzerland.
From31Marchto11June,thesystemswereoperatedasHPsystems,withnutrientsupplementsadded
directlytothesump(Figure1). Therequiredamountofnutrientsupplementswascalculatedbasedon
Water2016,8,533 3of21
thewatervolumeintheHPunit. On12June,theHPunitswereconnectedwiththeaquacultureunit
Wanatdert 2h0e16s, y8s, 5te33m  startedtoworkasaquasi-closedloopAP. 3 of 21 

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2.1. The Aquaponic System 
2.1. TheAquaponicSystem
Three identical experimental recirculating AP systems (A, B, and C) were installed in a 
ThreeidenticalexperimentalrecirculatingAPsystems(A,B,andC)wereinstalledinagreenhouse,
gcoreveenrhinogu2se7,0 cmov2eirnintgo t2a7l0(F mig2u irne t1o)t.aEl a(FchigAurPe s1y)s. tEeamch(F AigPu sreys2t)emwa (sFcigoumrep o2s) ewdaosf caofimsphohsoedld ionf ga tfainshk 
holding tank (2700 L), a solids removal unit (drum filter) with water level sensor (230 L), solids 
(2700L),asolidsremovalunit(drumfilter)withwaterlevelsensor(230L),solidsthickeningunit,
thickening unit, i.e., radial flow settler (45 L), a moving bed biofilter (580 L), an oxygenation zone (30 
i.e.,radialflowsettler(45L),amovingbedbiofilter(580L),anoxygenationzone(30L),acollection
L), a collection sump with water level sensor (470 L), piping (65 L) and a HP unit (730 L). The HP unit 
sumpwithwaterlevelsensor(470L),piping(65L)andaHPunit(730L).TheHPunitineachofthree
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(Dryhydroponics, BV’s‐Gravenhage, The Netherlands); and (iii) a drip irrigation system (4 m × 2 m) 
BV’s-Gravenhage,TheNetherlands);and(iii)adripirrigationsystem(4m×2m)withfourcoconut
with four coconut fiber slabs for plant support and 20 narrow tubes delivering water directly to the 
fiberslabsforplantsupportand20narrowtubesdeliveringwaterdirectlytotheplants. Eachreplicate
pAlPanstyss. tEeamchh aredpaliwcaatete ArvPo slyusmteemo fh4a.d8 5a mw3ataenrd vaolsuumrfea coef o4f.8355 mm32 a.nd a surface of 35 m2. 
The climate in the greenhouse was controlled and recorded by a greenhouse climate computer 
Theclimateinthegreenhousewascontrolledandrecordedbyagreenhouseclimatecomputer
(MasterClim 4 Zones, Anjou Automation, Mortagne‐sur‐Sèvre, France). During the day (start 1 h after 
(MasterClim 4 Zones, Anjou Automation, Mortagne-sur-Sèvre, France). During the day (start 1 h
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aeration (openings in the greenhouse roof and additional ventilation) started if the temperature was 
aeration(openingsinthegreenhouseroofandadditionalventilation)startedifthetemperaturewas
aabboovvee 2200 °◦CC.. DDuurriinngg tthhee nniigghhtt ((ssttaarrtt 11 hh aafftteerr aassttrroonnoommiiccaall ssuunnsseett)),, tthhee hheeaattiinngg wwaass aaccttiivvaatteedd iiff tthhee 
tteemmppeerraattuurree wwaass bbeellooww 1166 °◦CC aanndd aaeerraattiioonn ssttaarrtteedd iiff tthhee tteemmppeerraattuurree wwaass aabboovvee 2200 °◦CC.. TThhee sspprriinnkklliinngg 
system (CoolNet, Netafim Ltd., Tel viv, Israel) came into operation if the temperature was above 27 
system(CoolNet,NetafimLtd.,TelAviv,Israel)cameintooperationifthetemperaturewasabove
°2C7 ◦oCr tohret hhuemhuidmitiyd ibtyelobwelo 4w0%40 (%Fig(Fuirgeu 3r)e. 3).
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Water 2016, 8, 533  4 of 21 

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uuunnnuitiin utta uinaatnn nniadtidd nt a t dahtnthhn udtuudhs tss uhte heesnu nnusesssusn euu rsenrreuneesdrsudde uar daare c e daccodo o nac nnao scss tncoattosaanntnnnast ttstnw atwwtan anwaatt tettwa eerwtrr ael aelltreeetv elvvreer eellv elllie evniilvnne ite lnhtt lhhi eniteen h s t essuhtuu hmsemmeu sp msupp.u m..pD mDD.pu Dpuu.r .rriDu niiDnrnugiuggnr a rigaanuin uugatgott uoao mtaummouatmaoattoittmaciimcc tadi dcadtr itrrudciuuc mrd mmudr mfru iffiulmi tllmfetti eelrf trr iferl irrtirlnetii nnerrsir ssinr niirisnnngiinggns ws igwwnin igwtiightt hhwi tw hiti hth
ccclellceealaanecnnclaeeleedneadde an sdnsesy eyydssdsst yetst seesmytmymes stm wetwwem amwaat ettw aeerwtr,rae ,,a stresstm, emmrsr,a m,aals llslma llm alaaalm amlmallo lmooa uaumuonmnnutosttonus sut onsoonft ffsot ws wfwo aowfaat fettw aeerwtr rae watrwwet ierwtiirh tthw hi tw shisosti oohtlsihll odiis ddlssois dosl (ilsf(d(iif fidsis(shsfs ih(h sf( mhifmmsi sahmahan nm naumuunrareuranee nru aeauanr nnreaded dn a  rdanrern eedsrsdis ediir dsdrueiuedusesieuesdis sdeu osuoofe fefso fs ifffio si oshsffhi hf sf  fhifeffsie eeshfeehde ddf e)ef ))de e)ed d) )
wwweweerrreweee wrr erereeere mrremmee orm oorevevvmoemeedvoddeo vi dnivienn etditotdnoo it s niossontoo lostilloodi isdd lssoiss dolt ithltsdhih idtsciihcsc ktk ikhtecehenkincniieckniinknnegieggnn nu iguuninn nnguigtii nt,ut ,,uia ntaans,is s taid ,tdds ,ea eeadsssscs edcc rsdrriecbiiesbbrescieedcbrddrie bii dnibienn e diM dnMM i anMiaany yyM eaMeeryarr e[a y[2[ry22e 3[e3r3]2r ].][3 ..2T[ ]T2T3.h 3hh]Ti.]cii h.Tcck Tikkhecheenkicnnieeckeednkedde enf dnlffleol edoofadlaa tof ittlfaniiolnntogaiggna,t ,,itag niaann,g nnadg,ddn ,as  dassnenee tdstttdel ttsell tseeetdleddte tt ldtel edd
sslulsudldusgslgdeuleu gdwdewg agwease s wa mwsma aamsans nm aumunaaaulanllnayulylu alryaelrll emyrlmye or morevemvoemedvodeo vfdvrfeor edfomdr mof r fmtrohtomh emte h st eysht yhssetsey est sesmytymes stmtethtemh rmterh eet rhte ehtreitremi etmeiee mt esit msieamsa ew easws eaw eea ekwe wk eaekeane enkadk dn a cdanocn odlcldlo elc clecoltceoletlcldeeltedce ictdneitn e diadn ani nnia no naou anuotnd uto dootudooutoordt doruorouno ounritr ni.u t ui.ntn.i ti.t .
sludge was manually removed from the system three times a week and collected in an outdoor unit. 
SSooSlilodiSdlSsois-odlf-ilsrfdire-dsfeers-e ef-wrfwere aeweate etwa erwtr aewawtret aewarsr s wa rwrseae tarstueus rr trrneuneteruetdnudre rntdntoeo e dttdtoh ht eotte ho sts eohto hlselieoid ds lssois dolrirlesdie mdrmses orm orevvemoamavlol uaovulvna nuailit lnt.u . uintn.i ti.t .
Solids‐free water was returned to the solids removal unit. 
In IonIr nIdon reo dorr erdtdore etrmor t aotmok m aemk aaaek ck aeoe acm ao c pmcooampmriapsproaiarsnrio sitnsooo n tcno ot otcmoo c mmcoomemmrmcemiraecelri rcapcilrai paol ldrp opurdrocoudtdicuoutncicot,it nfoioo,n unf,o r,f u oftooru umtror ta mottomoam tpaoatl aotpon lp aptlsnal aotnsnft osttsh fo oetfh fst ehtah mseea s emsa acmemu celetu ci vclutuailvtlrit avivra arr
IInn oorrddeerr toto mmakaek ae caomcopmarpisaorins oton ctoomcmomercmiaelr pciraoldpurcotidounc, tfioounr, tfoomuartoto pmlaantots polfa tnhtes saomf teh ceulstaivmaer 
wewrweew regeerr reoge wrg ogrnwro owhnwy nhnd yh rhdoyyprdodorpronoopipcnoaoinlcnliaycilca loayllln yloy rno oo ncrn okr c rowkoc ckowk ow olw oouolos ouiln lsu guisn sidgninr gdigp rd idirprri rpiipir gir raiirrgtriiagoigtaniaot itinoino n inan i nicano a cma oc mmcoomemmrmcemiraecelri rcagcilari aegl lerg negrehreneeoehnunohshueoo su(ueMs se(eeM ( iM(eeMrie eeirei err
wcuelrtiev garrowwenr ehgyrdorwopnohnyicdarlolyp oonni craolclyk ownorool cukswinogo dlruispi nirgridgraitpioinrr iigna ati oconminmaerccoimalm greerceinahlogureseen (hMoeuiseer 
GeGmGeGümesemüem,sü Pües,ase Peu, ,aPl P uuaalun uuld lnu uRdnnu dRde uRd Reuiu dMeeid deMii iMe eMrie,e eRirei,eü rRr,t ,iüR hRtüoiühtfit,ohi Shfo,wo fS,fi w,St Szwiewtzritileztarzenleradrlnal)a.dn Fn)d.od )Fr.) o.Ft Fhro oitrshr t cihtsohi cmsiso c pmcooampmriapsproaiarsnrio signsoro nogn urg ogpruro,o putuo,p mpt,o ,ta mottomoam tcaoaut otclotu ci vclutuailvttlitiavoivtaniaot itnoio nn
(GMemeieürseG, Peamuül suen,d PRauueldiu MndeieRr,u RedütiihMofe,i Sewr,itRzüertliahnodf,). SFwori ttzheisr lcaonmd)p.arisFoonr gtrhoiuspc, otommpaatrois counltigvraotiuopn, 
memamesmuaeseraueasssru eurssreu esscs u hssc uuhacc shh a psa aespss tepipscetiesidscteiticid cieadid peaep palaippcplapiptcliilaocitcaniaot itnowio nenw r weew reeper reeper fepoprerfermorfrofemordrmem daee dcdca o cacracdoccrciondorgirdnd igntino g gt oe t sotote as ebtesalstibastalhbibselihldsiesh hdmee ddam n maamngaaanengmaaegegmenemetm neetn nt t
mtoemaasutorecsu lstiuvcaht ioans mpeesatsiucirdees saupcphliacsatpioesnt icwideerea pppelrifcoartmioendw aecrceoprderinfogr mtoe deastcacbolridshinegd tomeasntaagbelimsheendt 
prpacrptapriccrataecicscti teicisnce e siSns iw niSni wSt zSwiewtzritileztarzenleradrlnal [adn2n d4[d2] [. 4 2[I]24n.4 ] I.]an .I d nIand da iatddidoidtdniioti,it notiow,n nt,ow ,t wtdowi ofdof eid fdrfieefiffnrefeter nrecetnh ncte thrc rcehyhre retryorr rymtyo t amottomoam tacoaut otclot uci vclutuailvtlritsavi vrwasar erswsr w eew reaeerl sreaeo la s abloslo sobuo ob gbuohogutu hgignth h itn ti nin
pmraancatigceems ienn tSwpriatzcteircleasnidn [S2w4]i.t zIenr laadnddit[i2o4n],. tIwnoad ddiiftfieorne,nttw cohedrirfyfe troenmtacthoe crruylttiovmarast woceurelt iavlasors bwoeurgehatl sino 
a sau aspa ues spurumeppreamerrrmkameraktar erkokten eot t1no 5o n1 n O51 1c5O5t oO cObtcoectbrot oebtbroe e rtcro ot otcmo oc pmcooampmreapp raieanr retieen i rtninentraetnler arnfnrla uaflr iltf u rfqirutuu iqtia tuq liqautuylai atltyilrti ayttyir tt asrti ratfasirti ostfsmr f orf mrotohm meth t eehtxh eepe xee perxxiepmpreieermrinmietmaneletn anstlyat assl lyts essymtysest metem m
ab osuugphetrminaarkseutp oenrm 1a5r kOecttoobne1r5 toO cctoombepratroe cinotmerpnaarle firnutietr nqualaflrituyi ttrqauiatsl itfyrotmra itthsef reoxmpetrhiemeexnptaerl ismyestnetmal 
wiwthwiw tdhitii htfdhf eid fdrfieefiffnrefeter nrecetun ncltt tuci vclutuailvtrlitsavi vrgasarr rosgs wrg ogrnwro owinnw n iann ni nia nu na na nunk nu nuknonnkwkonnnwo owcnwo ncmn oc mmcoomemmrmcemiraecelri rcascilyai assly tls essymtysest.m etem.m . .
wsyistthe mdifwfeirtehndt icfufelrteivnatrcsu gltriovwarns ignr oawn nuninknaonwunn kcnomowmnecrcoimalm syesrcteiaml.s ystem.
Water2016,8,533 5of21
Water 2016, 8, 533  5 of 21 

Figure3.FWigeuerke l3y. Wmeeeaknly vmaelaune vsafluoerst feomr tpemerpaetruatruere(T (T),),a anndd rreellaatitvive ehuhmuimditiyd i(RtyH()R inH th)ei ngrtehenehgorueseen, ahnodu se,and
electrical conductivity (EC) in the system water; n = 1 for RH and T and n = 3 for EC. 
electricalconductivity(EC)inthesystemwater;n=1forRHandTandn=3forEC.
2.2. Stocking of the System 
2.2. StockingoftheSystem
In spring 2014, the AP system was stocked with tomato plants (Solanum lycopersicum L. cv. 
In sp“Grianrgden2b0e1r4ry, Fth1”e (HAiPld)s) yansdte Nmilew tilaaspisat (oOcrkeoecdhrowmiist hniltootimcusa)t. oTopmlaatno tssee(dSlionlgasn wumerel oybctoapineerdsi ocun m L. cv.
28 February from Tozer Seeds Ltd. (Pyports, UK) and were supplied by Max Schwarz AG (Villigen, 
“GardenberryF1”(Hild))andNiletilapia(Oreochromisniloticus). Tomatoseedlingswereobtainedon
Switzerland) before being cultivated further in the greenhouse. Seedlings were transplanted into the 
28FebruaryfromTozerSeedsLtd. (Pyports,UK)andweresuppliedbyMaxSchwarzAG(Villigen,
HP units on 31 March. Initially, each HP unit hosted seven tomato plants with 24 shoots (31 March–
Switzerla1n2d J)ubneef)o. rOenb 1e2in Jgunceu, lotinvea rtaenddfoumrt hheearltihnyt hsheogorte peenrh HoPu suen.iSt eweadsl irnemgsovweedr etot raasnsessps ltaontatle dgrienetno  theHP
unitson3b1ioMmaarscs hin. eInacihti aHlPly u,neiat,c lheaHviPngu 2n3i tshhooostste pders uenviet.n Ttoo emnsautroe peqlaunaltistyw bietthw2ee4ns HhoPo utnsit(s3, 1onM 2a5r Jcuhly–,1 2June).
On12Junoen,eo snhoeorta pnedr cohmanhneela wltahsy resmhoovoetdp, leeravHinPg u22n hitewaltahsy rsehmoootsv, ewdithto eaacshs etosmsatotot apllagnrte oecncubpiyoinmga asns ineach
average area of 1.1 m2. The tomato plants were cultivated using a high wire system [25], with the 
HPunit,leaving23shootsperunit. ToensureequalitybetweenHPunits,on25July,oneshootper
supporting wire at a height of 4.20 m. The growth period after transplanting was 31 weeks. The 
channelwasremoved,leaving22healthyshoots,witheachtomatoplantoccupyinganaverageareaof
tomato plant tips were cut nine weeks before the end of the experiment to prevent further elongation. 
1.1m2. ThPelatnot mpraottoecptiolann wtsithw beerneecfiucilatli voargteadnisumssin (Egnacahrsiiga hforwmiorsea,s Iychsnteeummo[n2s5, ]a,nwd iPthhytthoseeisuulups ppeorrstiminilgis)w  ireata
heightofa4n.d2 0pemsti.ciTdhese (gNraotuwratlh, Ppeegraisouds, aanftde Erntvraidnosrp) wlaanst pinergfowrmaesd3 d1epwenedekenst. oTnh tehet onmeedast o(Tpablalen At1ti)p  swere
cutninewanede kacscboredfionrge ttoh ienteengrdatoedf tpheeste mxpaneargimemeenntt tporipncriepvleesn utsfiungr tbheenrefeilcoianl goargtiaonnis.mPs laanndt pprroodtueccttsi onwith
registered for organic production as standard pest control measures. Other chemical pesticides were 
beneficialorganisms(Encarsiaformosa,Ichneumons,andPhytoseiuluspersimilis)andpesticides(Natural,
only applied to control high pest pressure situations. Bumblebees provided by Andermatt Biocontrol 
Pegasus,andEnvidor)wasperformeddependentontheneeds(TableA1)andaccordingtointegrated
AG (Grossdietwil, Switzerland) were used to support pollination. In June, a high occurrence of spider 
pestmanamgietems wenats pobrisnercvipedle isn uthsei nggrebenehnoeufiscei, awliothr goanne iosfm thsea rnafdt cpurlotudrue cHtsP rseugbiusnteitrse (dC9f)o breoinrgg athnei cmporsot duction
asstandaarfdfepcteedst cchoannntreol l(Fmigeuarseu 1r easn.dO Ftihguerrec Ahe1)m. Hicoawlepveesrt, iac idraetisngw oefr espoindelyr mapitpe ldieadmatogec oonn tlreoavlehsi ghpest
sampled for nutrient analysis did not show severe damage or significant differences between the 
pressuresituations. BumblebeesprovidedbyAndermattBiocontrolAG(Grossdietwil,Switzerland)
treatments. Towards the end of September blossom‐end rot was observed on some fruits in all of the 
were used to support pollination. In June, a high occurrence of spider mites was observed in the
HP units (Figure A2). From July onwards regular cutting of the roots in the NFT channels was 
greenhouse,withoneoftheraftcultureHPsubunits(C9)beingthemostaffectedchannel(Figure1and
necessary. Inside the channels, increasing root biomass was blocking the water flow, causing 
FigureA1le)a.kHagoews, eavnedr c,laogrgaitnign gtheo fpisppeisd. eTrhem roitoetsd waemrea cguet oonn bleotahv seisdessa omf pthlee dchfaonrnenl uotvreire an tpearnioadly osfi as didnot
showsevfeerwe ddaayms atog ceaousres liegsns isfitrceassn ttod tihfefe prleannctse, sasb sehtwowene nint Fhiegutrree aAt3m. Renotttse.nT roowotsa rwdesret hoebseenrvdedo fafSteerp tember
removing roots from the raft culture and NFT channels in November. The most damaged roots were 
blossom-endrotwasobservedonsomefruitsinalloftheHPunits(FigureA2). FromJulyonwards
found in the corners of the raft culture (Figure A4), probably resulting from insufficient aeration, and 
regularcuttingoftherootsintheNFTchannelswasnecessary. Insidethechannels,increasingroot
in the NFT channels under the coconut fiber slabs (Figure A5). 
biomasswasNbliolec tkilianpgiat lhaervwaea wteerrefl oobwta,inceadu fsrionmg Tleila‐Akqaugae sIn,taenrndatciolongalg (iVnegldtehne, Tphiep Nese.thTehrleanrdoso)t. sOwn 1e2r ecuton
bothsideJsunoef, tehacehc fhisahn tannekl wovase srtoackpeedr wioidth o30f0a tifleapwiads (aaypsprtooxicmaautse e67l.e8s gs psetrr efisssh)t.o Ththe efisphl wanertes ,feads asdh ownin
FigureA3li.bRituomtte (in.er.,o too taspwpaererneto sbatsiaetrivone)d tharfetee trimreems ao dvaiyn g(8:r0o0o, 1ts3:0fr0o, amndt h17e:0r0a)f wtcituh lat uswreimanmdinNg pFeTllectheda nnelsin
feed (Table A2). While nutrient uptake by the tomato plants remained more or less stable after 12 
November. Themostdamagedrootswerefoundinthecornersoftheraftculture(FigureA4),probably
resultingfrominsufficientaeration,andintheNFTchannelsunderthecoconutfiberslabs(FigureA5).

Nile tilapia larvae were obtained from Til-Aqua International (Velden, The Netherlands).
On 12 June, each fish tank was stocked with 300 tilapias (approximate 67.8 g per fish). The fish
were fed ad libitum (i.e., to apparent satiation) three times a day (8:00, 13:00, and 17:00) with a
swimmingpelletedfeed(TableA2). Whilenutrientuptakebythetomatoplantsremainedmoreor
lessstableafter12June,thefishbiomassincreased. Gainedfishbiomassovertheentireaquaponic
experimentwas59.0±5.0kg.
Water2016,8,533 6of21
To balance the feed input demand of the fish with nutrient demand of the plants, fish were
harvestedthreetimesbetween12Juneand5November,accordingtotheZHAWinternalstandard
operatingprocedure.
2.3. SystemMonitoringandDeterminationofNutrientSupplementationfortheHPSystem
Electricalconductivity(EC),pH,dissolvedoxygen,andtemperatureweremeasuredcontinuously
in the fish tank and logged every 15 min with SC1000 sensors from HACH Lange (Loveland, CO,
USA).CalciumhydroxideandpotassiumhydroxidewereusedtoadjustpHduringtheexperiment.
Weeklysystemwateranalysesoftotalphosphorus(TP),nitrate-nitrogen(NO -N),nitrite-nitrogen
3
(NO -N),ammonium-nitrogen(NH -N),potassium(K),iron(Fe),calcium(Ca),magnesium(Mg),and
2 4
boron(B)wereperformedwithaDR3800VISSpectrophotometerandLCKtests(HACHLange). Each
week(1April–5November),onesamplefromeachfishtank(A,B,andC)wastakenin500mLplastic
bottles. Nutrient target values for system water (Table 1) were determined according to standard
tomatonutrientrequirements[26]. Inmid-September,theparameterswereadjustedtolowertarget
values. HydroBuddyfreesoftware[27]wasusedtocalculatetheamountofnutrientsupplementation
neededtoreachsystemwatertargetvaluesusingIronDTPAandMultiMicroMix(ÖkohumGmbH,
Herrenhof,Switzerland),KristaSOP,KristaMKP,andYaraLiva®Calcinit(YaraUKLimited,Grimsby,
UK),andEPSOTOP® (K+SKaliGmbH,Kassel,Germany). ThetargetvaluesforECandpHwere
2500µScmand6.5,respectivelythroughouttheentireexperiment.
Table1. Targetedlevels(mg·L−1)foreachmeasuredparameterintheaquaponicsystem,andthe
correspondingHACHLangeLCKtestnumbers.
Parameter TP NO3-N NO2-N NH4-N K Fe Ca Mg B
HACHLangetestnumber 349 339 341 304 328 321 327 326 307
31March2014until14September2014 40 160 0 0 250 3 200 50 0.2
15September2014until5November2014 40 160 0 0 234 3 130 24 0.2
2.4. TomatoHarvestandBiomassSampling
The fresh weight of removed biomass (pruned biomass, unripe tomato fruits, and roots) was
recordedfrom31Marchto5November. Ripe(i.e.,fullyred)tomatoeswereharvestedtwiceaweek
from 15 May till 5 November. Harvested fruits were classified into three categories according to
thecurrentmarketrequirementsforcherrytomatoes(Table2)[28],andsubsequentlycountedand
weighedforeachHPunitseparately. Startingfrom6June,thetomatoplantswereprunedweekly
by removing the side branches and old leaves, leaving 12–15 completely developed leaves on the
shoots,andshorteningtheflowerclustersto15tomatoespercluster. Theprunedbiomassdryweight
wasdeterminedtwice,on12Juneand25July. Afterthefinalharveston5November,theremaining
biomasswasweighed. Todeterminethedryweight,onetomatoplantfromeachHPunitwasused.
Freshsampleswerecutintopiecesofapproximately2–4cmwithgardenscissors,andoven-driedat
105◦Cuntiltheyreachedaconstantweight(24–48h). Thedriedsamplesweregroundintoapowder,
whichwaslaterusedtodeterminethetotalbiomassnutrientcontent,asdescribedbelow. Todetermine
theleafchlorophyllstatus(aplantvitalityparameter),theleafandfruitmineralnutrientconcentrations,
theinternalfruitquality,theleavesandthefruitsweremeasuredandsampledonthreedates(12June,
7 August, and 16 October), after the respective fruit harvest. To analyze the leaf mineral nutrient
content,theleaveslocatedbetweenthetwotrusses,whereactualharvestingtookplace,weresampled
fromfourplants. Thechlorophyllstatuswasestimatedusingachlorophyllmeter(SPAD-502,Minolta
Corporation,Ramsey,NJ,USA)measuringthefiveleafletsatthetipofeachleaf. Subsequently,leaves
werecutandstoredinacoolingboxforlaterprocessingonthesameday. Leafstomatalconductance
andtemperatureweremeasuredwithasteadystatediffusionleafporometer,SC-1(DecagonDevices,
Pullman,WA,USA)onthetipleaflet. Chlorophyllfluorescencewasmeasuredonthesamefiveleaflets
wheretheSPADmeasurementsweretakenusingaportablechlorophyllfluorometer(MiniPAM,Waltz
Water2016,8,533 7of21
GmbH,Effeltrich, Germany). Fluorescencewasonlymeasuredforthesecondandthirdsampling
harvest. Toanalyzethefruit,16randomfirstcategorytomatofruitswereselectedfromeachHPunit
andwereanalyzedasdescribedbelow. Toestimatethecumulativetomatofruitnutrientuptakefor
thetomatofruitsharvestedfrom15Mayto10July,resultsfromtheharveston12Junewereused.
Samplestakenon7Augustwereusedfortheperiodfrom11Julyto12September,andsamplestaken
on16Octoberwereusedforthelastharvestperiodfrom13Septemberto5November.
Table2.TomatoqualityclassificationsaccordingtoSwissmarketqualitynormsforcherrytomatoes[28].
Category Criteria FruitQuality
Category1 diameter:20–35mm marketable
Category2 diameter:>35or<20mm non-marketable,edible
rotten,cracked,damaged,blossom-endrot,
Category3 non-marketable,notedible
greenoryellowcolored(compost)
2.5. LeafandFruitAnalysis
Toanalyzetheleafmineralnutrients,thefoursampledleavesandfourfruitsfromeachHPsubunit
channelwerepooledanddriedinanovenat60◦Cuntilaconstantweightwasreached.Priortodrying
thefruitswerecutintohalvesandthedriedsamplesweregroundtopowder.Todeterminephosphorus
(P),K,Ca,copper(Cu),sulfur(S),Mg,manganese(Mn),zinc(Zn)andFe,200mgofdriedpowderwas
weighedintoaTeflontubeanddissolvedin15mLofnitricacid(HNO ,70%)at120◦Cfor90min.After
3
coolingdownfor30min,3mLofH O wasaddedandthesolutionswereincubatedforanother90min
2 2
at120◦C.Aftercoolingdownforafurther30min,thesolutionsweretransferredinto50mLtubes
andfilledupto50mLwithnanopurewater. Formeasurementpurposes,thesolutionswerediluted
tenfoldandanalyzedwithanaxialICPOES(VarianVistaMPX,Waldbronn,Germany). Toobtainthe
carbon(C)andnitrogen(N)concentration,2.5mgofdriedpowderwasweighedoutintotincapsules
andanalyzedinaCHNSOanalyzerEUROEA(HEKAtechGmbH,Wegberg,Germany). Forsugarand
aciditymeasurements,twofreshlyharvestedtomatofruitsweresqueezedandblended(Moulinex,
Glattpark,Switzerland)infourreplicatesforeachHPsubunit. Thesugarcontentwasthenmeasured
byareflectometer(HR75,Fa. A.KrüssOptronicGmbH,Hamburg,Germany)usingnanopurewater
asablank. Acidity(fruitpH)wasmeasuredwithapHmeter(Metrohm632,Herisau,Switzerland).
Theremainingfourtomatofruitswerefreeze-dried(ChristFreezeDryers,Beta2–8LDplus,Osterode
am Harz, Germany). Prior to freeze-drying, several tiny holes were pierced into the tomato fruit
skin to allow better evaporation. Afterwards, the tomatoes were ground up. The measurement
of the fruit lycopene content was adapted from the protocol by Anthon and Garrett [29]. For this
purpose,25mgoftomatopowderwasdissolvedin1.5mLHEA(Hexane:Ethanol:Acetone,2:1:1)and
centrifuged. Aftercentrifugation,thesupernatantcontainingthelycopenewasremoved. Toobtain
all of the potential lycopene, this extraction step was repeated. Then, 0.45 mL of H O was added
2
tothepooledsupernatanttoreachphaseseparation. Fromtheupperpart,containinghexanewith
dissolvedlycopene,200µLwasplacedinatransparent96-wellplateandmeasuredintheEnspire
2300multimodeplatereader(Perkin-Elmer,Schwerzenbach,Switzerland)at503nm. Acorrection
functionfortheorganicsolventsusedwasestablishedusingcuvettespectrophotometer(UV-1800,
ShimadzuManufacturingInc.,Canby,OR,USA)andacrystalglasscuvette. Theopticalabsorbanceof
thelycopenesolutionisproportionaltothelycopeneconcentration,whichwascalculatedforeach
sampleweightusingtheEquation(1)establishedbyAnthonandGarrett[29].
(cid:16) (cid:17) 1.717×A ×V
Lycopene mg·kg−1 = 503 (1)
W
whereVisavolumeofHEAsolution(mL)andWisasampleweight(mg).
Oxygen radical absorbance capacity (ORAC) was adapted from the protocol developed by
Garrett et al. [30] For this purpose, 25 mg of tomato powder was dissolved in 1.5 mL MetOH
Water2016,8,533 8of21
(MetOH:H O, 1:1), mixed and centrifuged. The supernatant that contained the antioxidants was
2
removed. Thisextractionstepwasrepeatedthreetimes. Theremovedsupernatantswerepooledinto
onesample. Formeasurementpurposes,20µLofthesamplewereaddedto200µLofFluorescein
(Fluorescein Sodium Salt) and incubated at 37 ◦C for 10 min. After the incubation step, 75 µL of
2,2(cid:48)-azobis(2-amidino-propane)dihydrochloridewereaddedbeforetheabsorptionwasmeasuredin
anEnspire2300multimodeplateatawavelengthof485nmusinganemissionwavelengthof528nm.
AcalibrationcurvewascreatedusingTrolox(Trolox(±)-6-Hydroxy-2,5,7,8-tetramethylchromane-2-
carboxylic acid, 97%). The ORAC concentration is given as mmol TE L−1 where TE is the Trolox
equivalent.Themethodfordeterminingthetotalphenoliccontent(TPC)wasadaptedfromthemethod
developedbyWaterhouse[31],usingpooledextractsfromtheORACmeasurement. Thirtymicroliters
ofthesamplewasaddedto30µLH Oand50µLofFCR(Folin-Ciocalteau,10%). After1min,80µL
2
Na CO wereadded. Theplatewasincubatedfor2hatroomtemperaturebeforemeasuringat765nm
2 3
in an Enspire 2300 multimode plate reader. A calibration curve was made using Gallic acid and
measuredtogetherwiththesamples.
2.6. StatisticalAnalysis
The data were statistically analyzed in R-project using the R-studio software (R version 3.0.2,
2013)[32]. Thetotalfruityieldandbiomassparameterswerecalculated,usingaone-wayAnalysis
ofVariance(ANOVA)withtheHPsystemasafactor. Fortheleafandfruitanalysisandtheplant
vitalityparameters,atwo-wayANOVAwasperformedusingHPsystemandtimeofharvestasfactors.
Ifsignificanteffectswerefound,aTukey’stest(HSDtest)withap-valueofp<0.05wasperformed.
3. Results
3.1. TomatoYieldandExternalFruitQuality
Thetomatofruitsmeasuredapproximately25mmindiameter,hadastrawberryshapeanda
deepredcolor,asweetflavorandfirmconsistency(FigureA6). Themarketableyield(fruitsofthe
category1)wassignificantlyhighestinthedripirrigationandthenon-marketableyield(category2)
wassignificantlyhigherintheraftculturesystem(Table3). ThetotalcumulativeyieldperHPunit
showed significantly better performance for the drip irrigation system (Figure A7). This was also
observedforsingleharvestswherethedripirrigationsystemoftenhadthehighestweeklyyieldsand
theraftcultureprovidedthelowestones(however,notalwayssignificantlydifferent). Thenumberof
tomatofruitsincategory1wassignificantlyhighestinthedripirrigationsystemandthecategory2
yieldwassignificantlyhigherintheraftculture. Fruitfreshweightdecreasedsignificantlyduringthe
seasonbutnodifferenceswereobservedbetweentheHPsystems. Thenegligibledifferenceindry
matterwasonlydetectedincategory1wheremeanweightwashighestinthedripirrigationsystem
(19.4±3.2g)andlowestintheraftculture(18.8±4.3g).
Table3.Averagecumulativeandtotalyield(g·m−2)andaveragenumberoftomatofruits(±SD)shown
forthreequalitycategories(Table2)indripirrigationsystem,raftculturesystem,andnutrientfilm
technique(NFT)system.Differentlettersindicatesignificantdifferences(Tukey’sHSD,n=3,p<0.05).
FruitQualityClass DripIrrigationSystem RaftCultureSystem NFTSystem
Averagecumulativeyield(g·m−2)
Category1 18,323±667 16,857±341 17,176±364
Category2 86±220 b 156±290 a 73±110 b
Category3 248±108 371±177 255±650
Total 18,657±568 a 17,383±242 b 17,503±339 b
Averagecumulativenumberoffruits
Category1 936±350 877±500 869±350
Category2 11±400 b 20±4.00 a 10±200 b
Category3 15±7.00 21±900 16±400
Total 963±350 918±580 895±340
Water2016,8,533 9of21
Water 2016, 8, 533  9 of 21 
3.2. InternalFruitQualityParameters
3.2. Internal Fruit Quality Parameters 
ThefruitsugarcontentwasatitslowestinJune,andsignificantlyhighestintheAugustharvest
The fruit sugar content was at its lowest in June, and significantly highest in the August harvest 
(Figure4A).ThesignificantlyhighestsugarcontentwasmeasuredintheNFTsystem,andthelowest
(Figure 4A). The significantly highest sugar content was measured in the NFT system, and the lowest 
inthedripirrigationsystem(Figure4A).ThesugarcontentofthefruitsfromcommercialHPcontrol
in the drip irrigation system (Figure 4A). The sugar content of the fruits from commercial HP control 
wawsains itnh ethsea msaemrae nrgaengaes faosr ftohre thder idpriirpr iigraritgioanti.oTnh. eThfreu firtusiut gsaurgcaorn ctoenntteonft tohfe tOhec tOobcteorbhearr hvaersvtewsta swnaos t
menaostu mreedabsuecreadu sbeeocfauloswe onfu lmowbe nruomffbrueri tosfa nfrduiotsth aenrdfr outihtearn afrluysite sanwaelyresepsr iwoerirteiz perdi.oFrirtuizietdp.H Fr(uaciti dpiHty )
wa(sacsiidgintyifi) cwanatsl ysilgonwifeisctanintltyh eloOwcetsotb ienr thhaer vOecstto.bPerro nhoaurvnecsetd. Pdrifofneroeunncceesdb edtiwffeereenntchees HbePtwsyesetne mthsew HePre 
onslyysotebmsesr vweedrei nonthlye fiobrssterhvaerdv eisnt ,thweh feinrstt hhearrvafetstc,u wlthueren sthhoe wraefdt csuigltnuirfiec ashnotlwyehdig shigenriffriucaitnptlHy hviaglhueers 
thafrnuNit FpTH( vFaigluuerse t4hBa)n. NFT (Figure 4B). 

FigFuigreur4e. F4r. uFitruinitt eirnntaelrnqaula lqituyapliatyra pmaertaemrsestuergsa rsucognatre ncotn(Ate)n;tf r(uAit);p Hfru(Bit );psHu g(aBr)–;a csuidgraart–iaoc(iCd );ralyticoo p(Cen);e 
conlyteconpt(eDne); ctootnatlepnht e(nDo)l;i ctocotaml ppohuenndoslic(E c)o;amnpdoouxnydgse n(Er)a; daincadl aobxsyogrebna nrcaedcicaapla caibtyso(rFb)acnocme pcaarpeadciftoyr r(Faf)t 
culctoumrep,adrreidp ifrorirg artaifot nc,unlututrriee,n tdfriilpm itrercighantiiqoune, (nNuFtrTi)enatn dfialmc otnetcrhonligqruoeu p(NcuFlTti)v aatnedd ian acocnotmroml egrrcoiaulply 
opceuralttievdatehdy dinr oap coonmicmseyrsctiaelmly aotpethrarteeeds haymdprolipnognipco siynsttsemin astu tmhrmeee sr.amEprlrionrg bpaorisntrse ipnr esusemnmt setra. nEdrraorrd 
debvaiartsi orne.pDreisffeenrte nsttaunpdpaerrdc adseevainadtiolonw. eDricfafeserelnett teurpspinerdciacsaete asnigdn ilfoiwcaenrtcdasifef elreetntecress (inTudkiceayt’es sHigSnDi,finca=n3t ,
differences (Tukey’s HSD, n = 3, p < 0.05) for harvests and hydroponic systems, respectively. The 
p<0.05)forharvestsandhydroponicsystems,respectively.Thefactors,harvest(H)andtreatment(T),
factors, harvest (H) and treatment (T), and their interaction (H*T) were reported by “***” for p < 0.001, 
andtheirinteraction(H*T)werereportedby“***”forp<0.001,“*”forp<0.05and“.”forp<0.1.
“*” for p < 0.05 and “.” for p < 0.1.
Water2016,8,533 10of21
The fruits from commercial HP control had pH values similar to the aquaponically grown
tomatoes. Theratioofthesugartoacidityratio(Figure4C)showedsimilartendencies,beinglowestin
JuneandhighestinAugust;theNFTsystemdeliveredhighervaluesandthedripirrigationsystem
significantly lower values. Again, commercially produced tomato had similar values to the drip
irrigationsystem. ThefruitlycopenecontentwasobservedtobesignificantlyhighestintheAugust
harvest(Figure4D),whileonlyintheJuneharvest, werepronounceddifferencesbetweentheHP
systemsobserved.
At this time, the NFT system had significantly lower values compared to the raft and drip
irrigationsystems. Thelycopenecontentmeasuredinthecommerciallyproducedtomatoeswashigher
thanintheaquaponicallygrowntomatoesthroughouttheentireseason. TheTPCwassignificantly
higher in the October harvest compared to the June and August harvests. However, only in the
Augustharvest,weresignificantdifferencesbetweenHPsystemsobserved,whenthedripirrigation
systemhadthehighestTPC(Figure4E).ThecommerciallyproducedtomatoeshadalowerTPCin
theJuneandAugustharveststhaninOctober. TheORACchangedsignificantlybetweenharvests,
with the highest ORAC observed in August and the lowest in October. No significant differences
betweenHPsystemswereobserved(Figure4F).However,commerciallyproducedtomatoeshadlower
ORACvalues.
ThecomparisonoffruitqualityparametersfromAPgrowntomato(thisstudy)andtomatoes
boughtinthesupermarketwithSwissandDutchoriginrevealedsimilarsugarcontents,fruitpHand
sugarcontenttopHratios(Figure5). ForlycopeneandTPC,weobservedslightlyhighervaluesinthe
supermarkettomatofromtheNetherlands,whereasSwisssupermarketandtheAPsystemgrown
tomatoeshadsimilarvalues. IntermsofORAC,weobservedslightlyhighervaluesintheAPsystem
growntomatoes.
Intermsoffruitmineralconcentrations,themostvariancewasfoundbetweenharvests(Table4).
WhileC,N,PandSconcentrationsinfruitsdecreasedovertime,theconcentrationsofK,Mg,Fe,Ca,
Cu,Mn,andZnincreasedsignificantly. SignificantdifferencesbetweentheHPsystemswereonly
foundforMn,wheretheraftcultureexhibitedsignificantlyhigherconcentrationsinallthreeharvests
comparedtothedripirrigationandtheNFTsystems(Table5).
Table4.Averagefruitmineralconcentrations(±SD)shownforthethreeharvestsandthecorresponding
ANOVAresults. Differentlettersindicatesignificantdifferences(Tukey’sHSD,n=3,p<0.05)for
harvests. Thefactors,harvest(H)andtreatment(T),andtheirinteraction(H*T)werereportedby
“***”forp<0.001,“**”forp<0.01,“*”forp<0.05and“.”forp<0.1.
MineralNutrient 1stHarvest 2ndHarvest 3rdHarvest ANOVAResult
C(mg·g−1) 397.6±2.20 A 408.5±2.20 B 408.3±3.10 B H:***
N(mg·g−1) 17.4±0.8 A 15.4±0.6 B 14.6±0.5 B H:***
P(mg·g−1) 1.6±0.1 A 3.8±0.1 B 3.8±0.1 B H:***
K(mg·g−1) 10.6±0.3 B 28.6±0.40 B 34.9±2.5 A H:***
S(mg·g−1) 0.6±0.0 A 1.5±0.1 AB 1.4±0.1 B H:**,HxT:.
Mg(mg·g−1) 0.3±0.0 B 1.1±0.1 A 1.1±0.0 A H:***
Fe(µg·g−1) 4.0±2.0 C 24.7±2.80 B 39.2±15.3 A H:***,T:.
Ca(mg·g−1) 0.3±0.1 AB 1.0±0.3 A 0.6±0.2 B H:***
Cu(mg·g−1) 1.2±0.3 B 8.5±4.6 A 8.9±1.4 A H:**
Mn(µg·g−1) 4.1±0.8 B 22.6±9.6 A 27.3±10.3 A H:***,T:***,HxT:*
Zn(µg·g−1) 6.0±0.5 B 16.2±1.9 A 18.3±1.60 A H:***
Table5.Averagemanganesefruitmineralconcentrations(±SD)inµg·g−1shownforthethreeharvests
fromeachofthethreehydroponicsystems.Differentlettersindicatesignificantdifferences(Tukey’s
HSD,n=3,p<0.05)betweenHPsystems.
Harvest DripIrrigationSystem RaftCultureSystem NFTSystem
1st(12June2014) 2.6±0.1 b 4.2±0.1 a 2.6±0.1 b
2nd(7August2014) 12.0±5.1 b 31.4±3.0 a 24.3±5.8 b
3rd(16October2014) 20.2±2.3 b 39.6±6.7 a 22.2±4.4 b