Investigating the potential income and future water requirements of existing pecan orchards in the Western Cape

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dc.contributor.advisorLotze, Elmien_ZA
dc.contributor.advisorTaylor, N. J.en_ZA
dc.contributor.authorOberholzer, Abraham Stephanen_ZA
dc.contributor.otherStellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.en_ZA
dc.date.accessioned2022-03-04T13:09:36Z
dc.date.accessioned2022-04-29T09:23:05Z
dc.date.available2022-03-04T13:09:36Z
dc.date.available2022-04-29T09:23:05Z
dc.date.issued2022-04
dc.descriptionThesis (MScAgric)--Stellenbosch University, 2022.en_ZA
dc.description.abstractENGLISH ABSTRACT: The peak in pecan production occurs between 12 and 15 years, in traditional densities of 10 x 10 m, resulting in a long period before break even. To address this financial challenge, different approaches can be followed i.e., higher planting densities and earlier production, and cultivar choice for higher productivity, nut quality and adaptability to the environment. Tree performance under higher densities were evaluated in newly established orchards varying from three to six years, with the objective to assess vegetative and reproductive development of 'Wichita' pecans in the Hermon and Vredendal regions of the Western Cape, South Africa. Additionally, the suitability of three main cultivars, Wichita, Navaho and Choctaw, were evaluated in the Vredendal region. Both studies were conducted during two consecutive seasons. A desktop study on evapotranspiration was conducted using historical data (2009-2020) for both regions, applying the FAO-56 model in conjunction with a locally adapted pecan-specific model, to ascertain the potential water use of pecans under current and future climate scenarios. In paper 1, phenological development in Hermon commenced approximately two weeks earlier than in Vredendal. Results from both seasons and regions suggested that lower densities resulted in larger trees (volume), with no difference in light interception at this stage, irrespective of tree age. Yields varied according to density, with lower densities showing a higher yield efficiency per tree, but lower yield per ha. Thus, a higher yield is expected at higher densities, providing overcrowding can be managed. Overcrowding occurred in Vredendal, in the 10 x 5 m orchard, (year five), resulting in lower and reduced shoot growth compared to, lower density (10 x 8 m) orchard, with the same age. In paper 2, there was no significant difference in yield efficiency or nut quality between the cultivars in Vredendal. 'Choctaw' produced bigger nuts in the second season, with significantly bigger trees in both seasons than 'Wichita' and 'Navaho', except for the volume of trees in the first season. Despite the difference in tree volume, no significant difference in light interception between cultivars was observed, indicating that tree shape, rather than volume, influenced light interception. Additionally, 'Navaho' pecans demonstrated an earlier phenological development than ‘Choctaw’ and ‘Wichita’, with an earlier bud break and pollination period, which is critical to serve as cross-pollinator for 'Wichita'. Our data indicate that these three cultivars were suitable for cultivation in the Vredendal region, as the minimum chill units (237.5 CU) was recorded, required for pollination, although additional yield data is required before commercial recommendations can be made. Evapotranspiration data suggested a higher potential water use for pecans in the Vredendal compared to the Hermon region, with Hermon recording a lower ET than for Cullinan. This trend was also corroborated by actual evapotranspiration, as determined by satellite images. Climate change, with a predicted increase of 2 °C, increased ET and therefore the future water demand for both regions. Although the suitability of the crop, pecan, was confirmed for both regions, the prerequisite for access to irrigation in summer was evident from the ET study and needs to be incorporated in proposed extension of commercial orchards in these regions.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die piek in pekanneutproduksie word tussen 12 en 15 jaar bereik in tradisionele plantdigthede van 10 x 10 m, wat 'n lang tydperk voor gelykbreek tot gevolg het. Om hierdie finansiële uitdaging die hoof te bied, kan verskillende benaderings gevolg word, bv. hoër plantdigthede, vroeër produksie en kultivar keuse, vir hoër produktiwiteit, neutkwaliteit en aanpasbaarheid by die omgewing. Boomprestasie onder hoër digthede is geëvalueer in nuutgevestigde boorde tussen drie en ses jaar, met die doel om vegetatiewe- en reproduktiewe ontwikkeling van 'Wichita' pekans in die Hermon- en Vredendal-streke van die Weskaap, Suid- Afrika, te evalueer. Daarbenewens is die geskiktheid van drie hoofkultivars, Wichita, Navaho en Choctaw, in die Vredendal-streek geëvalueer. Beide studies is gedurende twee opeenvolgende seisoene uitgevoer. 'n Studie oor evapotranspirasie is uitgevoer met behulp van historiese data (2009-2020) vir beide streke, met die toepassing van die FAO-56-model in samewerking met 'n plaaslik aangepaste pekan-spesifieke model, om die potensiële watergebruik van pekans onder huidige en toekomstige klimaatsenarios te bepaal. In artikel 1, het fenologiese ontwikkeling in Hermon ongeveer twee weke vroeër as in Vredendal begin. Resultate van beide seisoene en streke het aangedui dat laer digthede groter bome (volume) tot gevolg gehad het, met geen verskil in ligonderskepping op hierdie stadium nie, ongeag boomouderdom. Opbrengste het gewissel volgens plantdigtheid, met laer digthede wat 'n hoër opbrengsdoeltreffendheid per boom toon, maar laer opbrengste per ha. Dus word 'n hoër opbrengs by hoër digthede verwag, mits oorskaduwing bestuur kan word. Oorskaduwing het voorgekom in Vredendal, in die 10 x 5 m boord (jaar vyf), wat gelei het tot laer en verminderde lootgroei in vergelyking met die laer digtheid (10 x 8 m) boord, van dieselfde ouderdom. In artikel 2, was daar geen betekenisvolle verskil in opbrengsdoeltreffendheid of neutkwaliteit tussen die kultivars in Vredendal nie. 'Choctaw' het groter neute in die tweede seisoen geproduseer, met aansienlik groter bome in beide seisoene as 'Wichita' en 'Navaho', behalwe vir boomvolume in die eerste seisoen. Ten spyte van die verskil in boomvolume, is geen betekenisvolle verskil in ligonderskepping tussen kultivars waargeneem nie, wat aandui dat boomvorm, eerder as volume, ligonderskepping beïnvloed. Boonop het 'Navaho' 'n vroeër fenologiese ontwikkeling as 'Choctaw' en 'Wichita' getoon, met 'n vroeër knopbreek en bestuiwingsperiode, wat van kritiese belang is om as kruisbestuiwer vir 'Wichita' te dien. Ons data dui daarop dat hierdie drie kultivars geskik was vir verbouing in die Vredendal-streek, aangesien die minimum koue-eenhede (237.5 CU) wat benodig word vir bestuiwing aangeteken is, alhoewel addisionele opbrengsdata benodig word voordat kommersiële aanbevelings gemaak kan word. Evapotranspirasie data dui op 'n hoër potensiële watergebruik vir pekans in die Vredendal in vergelyking met die Hermon-streek, met Hermon wat 'n laer ET as Cullinan aangeteken het. Hierdie tendens is ook bevestig deur werklike verdamping soos bepaal deur satellietbeelde. Klimaatsverandering, met 'n voorspelde toename van 2 °C, het ET verhoog en dus ook die toekomstige water aanvraag vir beide streke. Alhoewel die geskiktheid van die gewas, pekan, vir beide streke bevestig is, was die voorvereiste toegang tot besproeiing in die somer duidelik uit die ET-studie en moet dit geïnkorporeer word in voorgestelde uitbreidings van kommersiële boorde in hierdie streke.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentix, 141 pages : illustrations (some color)en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/124628
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subjectLeaf area indexen_ZA
dc.subjectPecan (Carya illinoinensis) -- Growth -- South Africa -- Western Capeen_ZA
dc.subjectPecan -- Yieldsen_ZA
dc.subjectPecan -- Water requirementsen_ZA
dc.subjectPecan -- Phenologyen_ZA
dc.subjectPecan -- Effect of cold onen_ZA
dc.subjectUCTDen_ZA
dc.titleInvestigating the potential income and future water requirements of existing pecan orchards in the Western Capeen_ZA
dc.typeThesisen_ZA
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