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dc.contributor.advisorEngelbrecht, G. M.
dc.contributor.advisorDu Preez, C. C.
dc.contributor.authorJordaan, Jacques
dc.date.accessioned2017-05-16T08:39:19Z
dc.date.available2017-05-16T08:39:19Z
dc.date.issued2002-11
dc.identifier.urihttp://hdl.handle.net/11660/6225
dc.description.abstractEnglish: Stuck fermentation is currently a serious production associated problem in the South-African wine industry. This can mainly be attributed to insufficient levels of nitrogen in grape must, thus are not being able to supply in yeast demands. This study was undertaken to investigate whether the nitrogen content of grape must can be improved by fertilisation. In order to achieve this three nitrogen application treatments (N1C = 20 kg N/ha-¹ post-harvest; N2F = 20 kg N/ha-¹ post-harvest, followed with 20 kg N/ha-¹ after budbreak and fruitset respectively; and N2V = 20 kg N/ha-¹ post-harvest, followed with 20 kg N/ha-¹ after budbreak and veraison respectively), were applied to six grape cultivars (Cabernet Sauvignon, Chenin blanc, Pinot noir, Weisser Riesling, Chardonnayand Pinotage) for two seasons (1999/2000 = 1st season and 2000/2001 = 2nd season). The vineyard is situated on a high potential loam soil, classified as a red-brown Oakleaf, with a mean organic matter content of 1.4%. The effect of these nitrogen application treatments on the growth characteristics, grape must composition, leaf nitrogen content, as well as the soil nitrate content, were measured. Nitrogen applications during the vegetative phase had a positive effect on the shoot length and shoot elongation during both seasons, although more so during the 1st season. The pruning mass was significantly affected by cultivar during both seasons. Treatments receiving no nitrogen fertilisation during the vegetative phase (N1C) resulted in higher free amino nitrogen (FAN) and FAN/oB ratio in grape must, indicating a negative reaction to nitrogen fertilisation for soils having a high organic matter content. No nitrogen fertilisation during the vegetative season resulted in significantly lower bunch and berry mass values than those receiving fertilisation. This might indicate a negative relationship between bunch and berry mass and the FAN content of grape must. The nitrate content of the soil differed for the different soil depths and was affected by sampling date and N treatments. Results indicated that 70% of the nitrate was available in the top 30 cm of soil. Nitrogen fertilisation during the vegetative season on soils with an organic matter content of 1.4% should be strongly discouraged. This study therefore indicates that although high organic matter content and inorganic fertiliser applications may increase the nitrate content of the soil, this might not have the same effect on the nitrogen status of the vine.en_ZA
dc.description.abstractAfrikaans: Slepende gisting is tans 'n ernstige produksieverwante probleem in die Suid-Afrikaanse wynindustrie. Dit kan hoofsaaklik toegeskryf word aan die lae vlakke van stikstof in druiwemos, wat dus nie aan die gistingsbehoefte kan voorsien nie. Hierdie studie is gevolglik onderneem om te ondersoek of die stikstofinhoud van druiwemos deur bemesting verhoog kan word. Om hierdie doel te bereik is drie stikstofbemestingbehandelings (N1C = 20 kg N/ha-I na-oes; N2F = 20 kg N/ha-¹ na-oes, gevolg deur 20 kg N/ha-¹ na bot en met vrugset onderskeidelik; en N2V = 20 kg N/ha-¹ na-oes, gevolg deur 20 kg N/ha-¹ na bot en met deurslaan onderskeidelik) tot ses wyndruifcultivars (Cabernet Sauvignon, Chenin blanc, Pinot noir, Weisser Riesling, Chardonnayand Pinotage) toegedien oor twee seisoene (1999/2000 = Iste seisoen en 2000/2001 = 2de seisoen). Die wingerd is geplant op 'n hoë potensiaal leem grond, geklassifeseer as rooi-bruin Oakleaf, met 'n organiese materiaal inhoud van 1.4%. Die invloed van hierdie drie stikstof bemestingbehandelings op groei-eienskappe, mossamestelling, stikstofinhoud van blare, asook die nitraatinhoud van die grond, is gemeet. Stikstofbemesting gedurende die vegetatiewe groeifase het gedurende beide seisoene 'n positiewe effek op die lootlengte en lootverlenging gehad (wel meer so gedurende die eerste seisoen). Die tipe cultivar het (gedurende beide seisoene) die winterlootrnassa betekenisvol beïnvloed. Behandelings waar geen stikstof gedurende die vegetatiewe groeifase toegedien is nie (N1C) het tot hoër vry aminostikstof (FAN) en FAN/oB inhoud van die mos gelei. Dit dui op 'n negatiewe reaksie waar stikstofbemesting toegedien word op gronde met 'n relatief hoë organiese materiaal inhoud. Geen stikstof gedurende die vegetatiewe groeifase toegedien het ook betekenisvolle laer tros- en korrelmassas tot gevolg gehad. Dit mag op 'n negatiewe verwantskap tussen tros- en korrelmassa en die FAN-inhoud van druiwemos dui. Die nitraatinhoud het verskiloor die verskillende gronddieptes, datums van monsterneming en stikstofbehandelings. Resultate het aangedui dat 70% van die nitraat in die boonste 30 cm grondlaag beskikbaar was. Die toediening van N bemesting tydens die vegetatiewe fase van die wingerd op gronde met 'n organiese materiaal inhoud van 1.4% of meer behoort dus ten sterkste afgeraai te word. Resultate van hierdie studie dui daarop dat, hoewel 'n hoë organiese materiaalinhoud van die grond en anorganiese N bemesting die nitraatinhoud van die grond kan verhoog, dit nie noodwendig tot 'n verhoging in die N status van die wingerdstok sal lei nie.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectNitrogen fertilisationen_ZA
dc.subjectFANen_ZA
dc.subjectCultivaren_ZA
dc.subjectYielden_ZA
dc.subjectSoil nitrateen_ZA
dc.subjectLeaf analysisen_ZA
dc.subjectShoot elongationen_ZA
dc.subjectGrapes -- Fertilizersen_ZA
dc.subjectNitrogen fertilizersen_ZA
dc.subjectWine and wine makingen_ZA
dc.subjectDissertation (M.Sc.Agric. (Soil, Crop and Climate Sciences))--University of the Free State, 2002en_ZA
dc.titleImprovement of the nitrogen content of grape must with fertilisationen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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