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Aspects of mineral nutrition affecting fruit quality of ‘Nadorcott’ mandarin

dc.contributor.advisorCronje, Paul Jacobus Robbertseen_ZA
dc.contributor.advisorHoffman, L. (Lynn) (Horticulturalist)en_ZA
dc.contributor.advisorZacarias, Lorenzoen_ZA
dc.contributor.authorMarais, Helenen_ZA
dc.contributor.otherStellenbosch University. Faculty of AgriSciences. Dept. of Horticulture.en_ZA
dc.date.accessioned2017-08-14T13:54:39Z
dc.date.accessioned2017-12-11T10:52:52Z
dc.date.available2017-08-14T13:54:39Z
dc.date.available2017-12-11T10:52:52Z
dc.date.issued2017-12
dc.identifier.urihttp://hdl.handle.net/10019.1/102775
dc.descriptionThesis (MScAgric)--Stellenbosch University, 2017.en_ZA
dc.description.abstractENGLISH SUMMARY: Mineral nutrition of Citrus is one of the key controllable factors influencing fruit quality. The mineral nutrients known to have the greatest impact on Citrus fruit quality, in order of magnitude of effect, are nitrogen (N), potassium (K) and phosphorous (P). The timing of application together with the amount of fertiliser applied is of critical importance in determining the impact it will have on Citrus fruit quality, including any possible long-term effects on tree growth, development and phenology. Three experiments were conducted to study fruit quality of ‘Nadorcott’ mandarin, taking both these above-mentioned considerations into account. The first experiment explored the known influence of P on decreasing citric acid content of Citrus fruit. In production areas with cold winters, harvest dates can be delayed by high fruit acid content, to such an extent that flowering is detrimentally impacted and hence also the fruit yield of the following season. Results obtained indicated that the citric acid content of fruit was significantly decreased by mono-ammonium phosphate (MAP) sprays, applied at seven and/or eight weeks after full bloom (WAFB). The second and third experiments concentrated on the influence of late N application on ‘Nadorcott’ fruit quality when studied in combination with different irrigation regimes and under different climatic conditions, respectively. The second experiment showed that, when the influence of N is considered in combination with irrigation, it has a more pronounced effect on Citrus fruit quality than exerted by N alone. Over-irrigation can have the most serious negative effect on fruit quality when all the factors studied were considered, therefore it is proposed that irrigation is likely to be the main determinant for success when managing N fertilisation. In the third experiment where the effect of late N in different forms on fruit quality was studied, the influence thereof was found to be insignificant. In addition, none of the N applications negatively affected rind quality, including that of colour development or the incidence of disorders. Beneficial effects on flowering for the following season were, however, also not recorded. Currently it can be concluded that since the application of late N had negligible effects on fruit quality in this study it may be used in an orchard with a known N deficiency, later in the season, subject to the prerequisite that the orchard is not over-irrigated. This study confirmed the complexity of mineral nutrition in citriculture, based on the large number of factors that influence fruit quality. Future research should attempt to establish the ideal time of MAP application, also taking different concentrations and production areas into account. Late N application trials should be expanded to an in-depth study of the effect of the N status of the tree on flower initiation, whilst establishing the production conditions under which this practice should be recommended.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die minerale voeding van Citrus is een van die vernaamste beheerbare faktore wat vruggehalte beïnvloed. Die drie minerale nutriënte wat die grootste invloed op Citrus se vruggehalte het, is, in volgorde van die impak, stikstof (N), kalium (K) en fosfor (P). Tydsberekening asook die hoeveelheid kunsmisstowwe wat toegedien word, bepaal in ’n groot mate watter uitwerking dit op Citrus-vruggehalte en die langtermyngroei, ontwikkeling en fenologie van die boom sal hê. Met die inagneming van die bogenoemde was daar drie eksperimente uitgevoer om vruggehalte van ‘Nadorcott’-mandaryne te bestudeer. Die eerste eksperiment was gebaseer op die erkende feit dat P die sitroënsuurinhoud van Citrus verlaag. ’n Hoë vrugsuurinhoud kan problematies wees in koue produksie-areas weens die geassosieerde uitstel van die oesdatum. Gevolglik kan dit blomtyd en vrugopbrengs vir die komende seisoen nadelig beïnvloed. Die sitroënsuurinhoud was beduidend verlaag deur mono-ammoniumfosfaat (MAP) blaarspuite wat sewe en/of agt weke na volblom (WNVB) toegedien was. Die tweede en derde eksperimente het onderskeidelik gefokus op die invloed van laat N-toediening op vruggehalte wanneer dit gekombineerd was met verskillende besproeiingsvolumes, asook soos toegedien in verskillende klimaatsomstandighede. In die tweede eksperiment is bevind dat die invloed van N op Citrus-vruggehalte groter is in kombinasie met besproeiing as wanneer N alleen in ag geneem word. Oorbesproeiing kan die grootste nadelige uitwerking op vruggehalte hê, nadat alle faktore oorweeg was. Besproeiing blyk die belangrikste bepalende faktor te wees in die bestuur van N-bemesting. In die derde eksperiment was slegs die effek van laat N toediening in verskillende vorms op vruggehalte ondersoek en die invloed daarvan was nie beduidend nie. Verder is daar met geen van die N-toedienings ’n nadelige invloed op skilkwaliteit, insluitend kleurontwikkeling en die voorkoms van skildefekte, aangeteken nie. Daar was egter ook geen voordelige uitwerking op blom vir die daaropvolgende seisoen waargeneem nie. Die gevolgtrekking is dus dat die toediening van laat N ’n weglaatbare effek op vruggehalte het en in ’n boord met ’n N-tekort aanbeveel kan word, op die voorwaarde dat nie oorbesproei word nie. Die kompleksiteit van die minerale voeding van Citrus weens al die bydraende faktore betrokke by vruggehalte is weereens gestaaf deur die resultate verkry in hierdie studie. Voorgestelde toekomstige navorsing kan fokus om die ideale tyd van MAP-toediening vas te stel, asook om verskillende konsentrasies daarvan en ook verskeie produksie areas in te sluit. Laat N-toedieningsproewe kan uitgebrei word tot ’n in-diepte studie van die uitwerking van die N-status van die boom op blom-inisiasie, asook in watter produksie kondisies dit ’n aanbevole praktyk kan wees.af_ZA
dc.format.extentvii, 152 pages : illustrationsen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.subjectNitrogen fertilizersen_ZA
dc.subjectUCTD
dc.subjectMandarin orange -- Nutritionen_ZA
dc.subjectCitrus fruit -- Nutritionen_ZA
dc.subjectMandarin orange -- Qualityen_ZA
dc.subjectCitrus fruit -- Qualityen_ZA
dc.titleAspects of mineral nutrition affecting fruit quality of ‘Nadorcott’ mandarinen_ZA
dc.typeThesisen_ZA
dc.rights.holderStellenbosch Universityen_ZA


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