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Effects of different nitrogen sources and levels on tomato fruit quality

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Abstract

The use of nitrogen fertilizers contributes significantly to the proper growth and development of tomato plants, with significant gains in the production of fruit. However, incorrect use of nitrogen can change tomato fruit quality, making it undesirable for consumers. The aim of this work was to study the effect of different sources and levels of nitrogen on tomato quality to improve N management. The field experiment was conducted at the State University of Southwest Bahia - Vitória da Conquista, Bahia, Brazil. The experimental design was a randomized block with 4 replicates, with three nitrogen sources (calcium nitrate, ammonium sulfate and urea) and four levels of nitrogen (0, 140, 280 and 420 kg ha-1) in a 3×4 factorial. Fruit from the experimental treatments were evaluated for the following characteristics: firmness, pulp pH, titrate able acidity of the juice, ascorbic acid, soluble solids and the ratio of these. Increased levels of nitrogen negatively influenced the levels of ascorbic acid and titrate able acidity. The values of soluble solids and pH did not change with increasing nitrogen level, showing different effects in the sources used only. Due to effects several of different nitrogen sources on fruit quality characteristics, fertilization practices using nitrate and ammonium are recommended in order to improve quality.
Acta Hortic. 1106. ISHS 2015. DOI 10.17660/ActaHortic.2015.1106.13
XXIX IHC – Proc. VI Int. Symp. on Human Health Effects of Fruits and Vegetables
(FAVHEALTH 2014)
Eds.: T.J. O’Hare and M.E. Netzel
79
Effects of different nitrogen sources and levels on
tomato fruit quality
T. N . H .  R e b o u ç as 1,J.S.Porto1,J.S.Jesus1andM.O.B.Moraes2
1StatesUniversityofSouthwestBahia,VitóriadaConquista-BA,Brazil;2FederalInstitute ofBahia,Eunápolis-
BA,Brazil.
Abstract
Theuseofnitrogenfertilizerscontributessignificantlytothepropergrowthand
developmentoftomatoplants,withsignificantgainsintheproductionoffruit.
However,incorrectuseofnitrogencanchangetomatofruitquality,makingit
undesirableforconsumers.Theaimofthisworkwastostudytheeffectofdifferent
sourcesandlevelsofnitrogenontomatoqualitytoimproveNmanagement.Thefield
experimentwasconductedattheStateUniversityofSouthwestBahia-Vitóriada
Conquista,Bahia,Brazil.Theexperimentaldesignwasarandomizedblockwith4
replicates,withthreenitrogensources(calciumnitrate,ammoniumsulfateandurea)
andfourlevelsofnitrogen(0,140,280and420kgha-1)ina3×4factorial.Fruitfrom
theexperimentaltreatmentswereevaluatedforthefollowingcharacteristics:
firmness,pulppH,titrateableacidityofthejuice,ascorbicacid,solublesolidsandthe
ratioofthese.Increasedlevelsofnitrogennegativelyinfluencedthelevelsofascorbic
acidandtitrateableacidity.ThevaluesofsolublesolidsandpHdidnotchangewith
increasingnitrogenlevel,showingdifferenteffectsinthesourcesusedonly.Dueto
effectsseveralofdifferentnitrogensourcesonfruitqualitycharacteristics,
fertilizationpracticesusingnitrateandammoniumarerecommendedinorderto
improvequality.
Keywords:Solanumlycopersicum,nitrate,ammonium,urea,nitrogenfertilizers
INTRODUCTION
The overall production oftomatoes doubled in the last 20 years. Increased tomato
consumptionhasprovedtobeamajorfactorfortheexpansionanddevelopmentofthecrop
inseveralcountriesintheworld.Thisexpansionhasbeendrivenbysales growthoffresh
tomatoes,occurredforthesearchformorehealthyproducts(CasaandEvangelista,2009).
Tomatoesareanimportantsourceofvitaminsandminerals.Thefruit also contains
antioxidantcarotenoidsthatcontributeto humannutritionand givethe redcolorfor most
existingcultivarsonthemarket(RochaandSilva,2011).
Foryears,increasingtomatoyieldwasthemainobjectiveinthe development of
cultural practices and fruit quality has seldom been considered (Ferreira et al., 2006).
However, the search for healthier foods and raw materials for the industrial sector has
motivated the search for management practices that result in higher fruit quality. Mineral
nutritioncontrolsthephysiologicalprocessesofplants.Nitrogen,forexample,caninfluence
the quantities of certain organic and inorganic compounds present in the composition of
fruit.Fortomato,severalauthorshaveverifiedtheeffectofnitrogen fertilization on: pH,
solublesolidcontent,titratableacidity,vitaminCcontentandnitrate.(Warneretal.,2004).
Basedontheseconsiderations,thisworkaimedtoevaluatetheeffectsofsourcesand
levelsofnitrogenonthephysicalandchemicalqualityoftomatofruit.
MATERIALSANDMETHODS
TheexperimentwascarriedoutatUniversidadeEstadualdoSudoeste da Bahia,
Vitória da Conquista - BA, from October, 2012 to March, 2013, in a red yellow Latosol,
accordingtotheBrazilianSystemofSoilClassification.
A randomized complete block design, with four replications in a 3×3+1 (control)
80
factorialschemewasused,totaling40plots.Thetreatmentsconsisted of three sources of
nitrogen(calciumnitrate,ureaandammoniumsulphate)andthreelevels(140,280and420
kgha-1).
The transplanting was performed in November 2013, using tomato hybrid Silvety®
(SyngentaSeeds)inspacingof1.2×0.6m.Thefertilizationswereperformedaccordingtothe
results of soil analysis (Table 1) and recommendations of Filgueira (2008). Application of
the treatments began two weeks after transplanting, top dressing.Thetopdressing
fertilizationwasdividedinweeklyapplicationsuntilthe9thweek.
Table1.Resultsofsoilanalysisofexperimentalarea.Vitó riadaConquista,Bahia,Brazil.
pH 5.7
K
cmol dm-3
0.3
Ca 1.6
Mg 0.6
Al 0.6
Na 1.7
T 5.4
H+Al 2.9
MO dag kg-1 2.8
P1
mg dm-3
3.0
Fe 85.0
Zn 1.3
Cu 1.0
Mn 64.0
1Extractor, Mehlich-1
Harvest began at 110 days after sowing, harvesting only fruits with physiological
maturity for marketing (pinkish green color). After harvest, fruit quality attributes were
evaluated:firmness,pH,titratableacidity,solublesolidscontent,solublesolidsandtitratable
acidityratioandascorbicacid.
Fourfruitsofeachtreatmentwereusedandsenttothelaboratory,andthenfirmness
readingsofthefruitwerecarriedout,usingatexturemeter.Fruits were ground and one
20-g sample of crushed pulp was removedfor chemical analysis. The pH was determined
usingadigital pHmeter,thetitratable aciditywasdetermined bytitration withNaOH0.05
M,thesolublesolidscontentwasdeterminedusingadigitalrefractometer,attemperatureof
2C,theratiowasobtaineddividingthevaluesofsolublesolidsand titratableacidity and
ascorbicacidcontentwasdeterminedbytitrationwithTillmanssolutionat0.5%.
Data were subjected to analysis of variance, polynomial regression, and means
comparedbyTukeytest(P<0.05).
RESULTSANDDISCUSSION
Considering the quality traits of tomato studied in response to nitrogen fertilization
(Table2),noNeffectonfruitfirmnesswasobserved,theseresultsbeinginaccordancewith
Warner et al. (2004) and Heeb et al. (2005), studying the influence of different rates and
formsofnitrogenincommercialqualityoftomatofruit.However,forfirmnesstraitthesame
authorsfoundhighervalues(6.9kgcm-2)tothosefoundinthiswork(1.38kgcm-2),which
canbeattributedtothedifferenceinfruitmaturationstage.
We only observed changes in pH values of tomato fruit pulp whenthreesourcesof
nitrogenweretested(Table 2). Theuseofcalcium nitrateresultedin alowerpH valuefor
fruit,whencomparedwithurea.Nevertheless,forthesourceperformanceinrelationtopH,
wesuggestthatthepresenceofhigherNH4+didaccumulatehigherlevelsofmineralsolutes
inthefruitpulp,which,consequently,eventuallydilutedtheorganic acids present in the
pulp.
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Evaluatingacidityintomatopulpunderdifferentnitrogenlevels,itwasobservedthat
therewasnocorrelationwithdifferentnitrogensourcesused(Table2).Reductioninacidity
wasobserved,withincreasednitrogenlevels(Figure1)obtainingaveragevaluesof0.386%
acid.AccordingtoJonesJr.(1999),theincreaseofnitrogenadverselyaffectthequalityofthe
fruit in the acidity grating, as the author states that the higher acidity results reduces the
flavoroftomatoes.
Table2. Summaryofvarianceanalyzesandmediumfirmness,pH,titratableacidity,soluble
solids,ratioinrelationtonitrogen.VitóriadaConquista,Bahia,Brazil.
FV GL
Firmness
(kg cm-2) pH Titratable
Acidity
(% acid)
Soluble
solid
(°Brix)
SS/AT
ratio
Means squares
Sources 2
17,14ns 0,03482*
0,00083ns
1,52336*
4,82ns
Levels 3
32.39ns 0.019ns
0.02601*
0.16ns
10.73735*
S×L 6
22.01ns 0.013ns
0.017ns
0.21ns
1.48ns
Error 37
13.79294 0.00948
0.00484
0.16543
0.98237
CV (%) 25,56 2.29
9.4
17.31
9.08
Calcium nitrate 1,38 a 4,20 b
4,27 a
0.395 a
11,38 a
Ammonium sulfate 1,38 a 4,27 ab
3,99 b
0.396 a
10,31 b
Urea 1,38 a 4,29 a
4,26 a
0.398 a
11,11 ab
DMS 0,09 0,08
0,16
0,03
0,86
* = Significant (P<0.05) by F test; ns = not significant (P<0.05) by F test; Means followed by the same letters in the column do not
differ by Tukey test (P<0.05).
Figure1.Valuesoftitratableacidity(A)andSS/ATratio(B)asafunctionofnitrogen.
Although the average values of titratable acidity were similar tothosefoundby
Ferreira et al. (2006), who found 0.389% of citric acid in tomatofruit,inthisstudy,these
valuesdidnotchangewiththeincreaseoflevelsofKobryńandHallmann(2005)confirm
thedatafoundinthispresentstudy,whentheystatethatnitrogenfertilizationcanaffectthe
totaltitratableacidityoftomatofruit.
For values of soluble solids of tomato pulp (Table 2) the different nitrogen sources
gavethecalciumnitrateandureahighervalues(°Brix)inrelation to ammonium sulfate.
Heebetal.(2005)founddifferentresultsforsolublesolidscontentfordifferentNsources,
verifyingthatthetreatmentwithNH4+providedhighercontentsofsolublesolids.Although
nitrate has obtained higher average without significant differencefromurea,whichstill
allowstobeverifiedinthisstudy,forthistrait,NH4+performedwell.
However,no influence oflevelsof N onsolublesolidscontent was noticed(Table 2).
82
TheseresultswereconsistentwiththosefoundbyWarneretal. (2004), who studied the
effects of N fertilization on fruit production and tomato quality for industrial processing,
usinglevelsrangingfrom0to200kgha
-1ofN,whoseBrixvalueswerenotaffectedby
differentlevelsofN;theaveragecontentofBrixwashigher(5.8) than the average  values
foundinthisstudy.However,Ferreiraetal.(2006)foundaverage values of 3.93 °Brix, a
lowervaluethanthosefoundinthispresentstudy;andaccordingtotheauthorsmentioned,
valuesofsolublesolidsdidnotchangewithanincreaseoflevelsofNeither.
Forratiovalues(Figure1B),anincreaseinthisratio,withan increaseoflevelsofN,
wasobserved.KobryńandHallmann(2005)foundsimilarvaluesofratiofortomatofruit,
rangingfrom9.95to12.54;inthisstudy,thesameway,anincreasein this ratio,when the
levels of N were increased, was also noticed. Nevertheless, Bénard et al. (2009) found
contrastingresultsforratio,inwhichanincreaseofthisratio,withareductionofdoseofN
innutrientsolution,wasnoticed.
Inthisstudy, theNlevelsperformance wastheresponsibletoinfluencethe titratable
acidity,sincethereductioninthevaluesoftitratableacidityenabledtoincreasethisratio,in
accordancewithanincreaseoflevelsofN.
For ratio results, a significant difference was also observed when different nitrogen
sourceswereused(Table2).Theuseofcalciumnitrateresulted in higherratiovalues for
fruit,whencomparedwithammoniumsulfateandurea,whichshowedsimilarresultsfor
thisvariable.However, theeffectof levelsofN ontitratableaciditymayhavemaskedratio
results,sincetheNH4+hasahigherfruitpalatabilityrating(Heebetal.,2005).
Regardingtheascorbicacidpresentinfruit, fromthedoseof140kgha-1,areduction
inthesecontents,accordingtoanincreaseoflevelsofN(Table3),wasobservedonlywhen
ammoniumsulfatewasusedasfertilizer.InaworkperformedbyBénard etal.(2009), the
reductionofNcontentsimpactedonascorbicacidcontents,causingaslightincreaseof11-
29% in these variable values, when levels of N were reduced, consistent with the results
presentedinthisstudy,whenthelevelsofNusedwerehigherthan140kgha-1. Simonneet
al.(2007)reporteda25%reductioninacidascorbiccontent,whenthe supplyofnitrogen
wasincreasedfrom0to392kgha-1.
Table3. Analysisofdeploymentascorbic acidcontent(mg100 g-1) of Silvetyhybrid fruits
tomatofromdifferentnitrogensourcesandlevels.VitóriadaConquista,Bahia,
Brazil.
Levels N (kg ha-1) Sources
Calcium nitrate Ammonium sulfate Urea
0 14.45 Aab 11.27 Aa 16.01 Ab
140 13.33 Aa 15.75 Aa 13.23 ABa
280 13.02 Aa 14.03 ABa 13.64 ABa
420 14.35 Aa 12.63 Ba 12.50 Ba
DMS 3.02
CV (%) 6.83
Means followed by the same lowercase letters in the rows do not differ by Tukey test (P<0.05); Means followed by the
same capital letters in columns do not differ by Tukey test (P<0.05).
CONCLUSIONS
IncreasesinlevelsofNaffecttomatoqualitybothpositivelyandnegatively.Therefore,
thestudysuggeststhatmoderateNsupplycanbeusedtobetterachievethebalance
betweentheyieldsandtheoptimizationofnutritionalandsensorialqualityoftomatofruits.
ACKNOWLEDGEMENTS
Thisisreservedforsourcesoffundingandhelpfromcolleagues or professional
associateswhoassistedintheprojectinminorways.
83
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... The sources and doses of nitrogen fertilizers can influence tomato quality. Rebouças et al. [19] have verified the effect of nitrogen fertilization on pH, soluble solid content, titratable acidity, and vitamin C content. These authors suggest that fertilization practices using NO 3 − and NH 4 + are recommended in order to improve quality. ...
... N. Soto et al. (2015) did not find a significant effect on firmness under increasing N treatments. On the other hand, increasing levels of N negatively influenced the levels of ascorbic acid and titrate acidity [19], but the values of soluble solids and the pH did not change. Nevertheless, Segura et al. [31] found that firmness and SSC increased throughout the time cycle, independently of the fertilization level. ...
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... For example, leaf yellowing (Prinsi et al., 2020), decreased lodging resistance (Ayoub et al., 1994), and decreased quality and yield (Read et al., 2006) were observed. When the nitrogen supply exceeds the nitrogen loading capacity of plants, the concentrations of ascorbic acid and titratable acid in the fruits will increase (Rebouças et al., 2015), leading to lower fruit quality. In addition, excessive nitrogen is often lost through rainwater erosion, denitri cation, and volatilisation and other ways (Kumar and Wagenet, 1985). ...
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Qualidade do tomate em função de doses de nitrogenio e da adubação orgânica em duas estações
  • M M M Ferreira
  • G B Ferreira
  • P C R Fontes
  • J P Dantas
Ferreira, M.M.M., Ferreira, G.B., Fontes, P.C.R., and Dantas, J.P. (2006). Qualidade do tomate em função de doses de nitrogenio e da adubação orgânica em duas estações. Hortic. Bras. 24, 141-145 http://dx.doi.org/10.1590/ S0102-05362006000200003.
Novo Manual de Olericultura: Solanaćeas II, Tomate: A Hortaliça Cosmopolita
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Tomato Plant Culture in the Field
  • J B Jones
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Jones, J.B., Jr. (1999). Tomato Plant Culture in the Field, Greenhouse and Home Garden (Florida, USA), pp.199.
Effects of low nitrogen supply on tomato (Solanum lycopersicum) fruit yield and quality with special emphasis on sugars, acids, ascorbate, carotenoids, and phenolic compounds
  • C Beńard
  • H Gautier
  • F Bourgaud
  • D Grasselly
  • B Navez
  • C Caris-Veyrat
  • M Weiss
  • M Geńard
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