Thesis (MSc)--Stellenbosch University, 1980. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OSPOMMNING: Geen opsomming beskikbaar

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The financial decision-making environment within which wine-grape producers function is challenging because of the complex interrelationships between yield, product price and input requirements. The complexity of farm systems is increased because production and financial decisions are necessarily made under uncertainty. Various issues influence the resilience of the wine industry. The goal of this study is to determine the financial implications of irrigation, integrated with canopy management practices on red wine cultivars in the Robertson area. Canopy management and irrigation cost play an important role within the multi-faceted farm system regarding yield, quality and input cost. This necessitates that research be carried out within the context of a systems approach. In this manner the interdependence among the various components of the farm system, and the associated synergies can be captured. Farm management, as a field of research, is dependent on other disciplines that present an alternative perspective to the research problem. Viticulture trials specifically focused on the impact of various irrigation and canopy management activities is being done on Wansbek farm. Nine treatments were tested at various combinations of soil water depletion levels and canopy management strategies. The farm is situated in Agterkliphoogte, an area in the Robertson valley. A multi-disciplinary group discussion was held to firstly obtain insight in the complex working of a farm. Secondly the group discussion was used to gain insight into the application of the Wansbek trial data and the setting of guidelines as to its application to determine the expected farm level financial implications of the treatments. Dealing with complexity necessitates insight form various areas of expertise, which is achieved time efficiently within expert group discussions. A quantitative method is required to reflect the interrelatedness and dynamics of a whole farm system in a user-friendly manner. Multi-period budget models present the ability to accommodate the complexity associated with a farm through a sequence of mathematical and accounting equations. The physical/biological interrelations and structure of the farm can be modelled while the financial performance of various irrigation and canopy management strategies can be determined. Farm-level profitability is especially sensitive to yield and price of farm products. The treatments that showed the highest expected profitability, return relatively high yields and prices at relatively low production costs. The sprawling canopy management treatment at c. 60% and c. 30% plant available water depletion levels returned the highest and second highest profitability at both gross margin per hectare and whole farm level. Scenarios were incorporated to illustrate the expected impact of key variables and the capability of the model. Key factors associated with the success of specific treatments could be identified. Results showed throughout that the balance between yield, price and input cost are the determining factor to profitability, rather than a focus on any particular one of these factors. / AFRIKAANSE OPSOMMING: Die finansiële besluitnemingsomgewing waarbinne wyndruifprodusente funksioneer, is uitdagend weens die komplekse verwantskappe tussen oesopbrengs en -kwaliteit en gepaardgaande insetbehoeftes. Die kompleksiteit van die boerderystelsels word verhoog deurdat produksie- en finansiële besluite noodwendig op grond van onvolmaakte inligting geneem word. Verskeie kwessies beïnvloed die voortbestaan van die wynbedryf. Die doel van hierdie studie is om die finansiële implikasies te bepaal van besproeiing, geïntegreer met lowerbestuur, vir rooi wyndruifverbouing in die Robertson-wynvallei. Lowerbestuur- en besproeiingkoste speel ʼn belangrike rol binne die multifasettigheid van ʼn boerderystelsel ten opsigte van opbrengs, kwaliteit en produksiekoste. Dit vereis dat die navorsing binne die konteks van die stelselsbenadering aangespreek word. Sodoende word die interafhanklikheid tussen die onderskeie boerderystelselkomponente, gekoppel aan die sinergistiese effek wat daarmee gepaardgaan, in ag geneem. Boerderybestuur as navorsingsveld, is gevolglik afhanklik van ander vakdissiplines wat ‘n alternatiewe perspektief verleen aan die navorsingsprobleem. Wingerdbouproewe wat spesifiek fokus op die impak van verskillende besproeiing- en lowerbestuursaksies word uitgevoer op die Wansbek-plaas. Die plaas is geleë te Agterkliphoogte, ʼn area in die Robertson-vallei. Nege behandelings is getoets teen verskillende kombinasies van plant beskikbare water (PBW)-onttrekkingspeile en lowerbestuurstrategieë. ʼn Groepsbespreking met multidissiplinêre deskundiges is gehou om eerstens, insig in die kompleksiteit van die werking van ʼn plaas te verkry. Tweedens, is die groep van multidissiplinêre deskundiges gebruik om insig te verwerf aangaande die hantering van die Wansbek-proefdata. Die groep het riglyne daargestel om die proefdata prakties aan te wend sodat die verwagte finansiële implikasies op plaasvlak geëvalueer kan word. Die hantering van kompleksiteit vereis insig vanuit verskeie gebiede van kundigheid wat tydsdoeltreffend binne ʼn groepsbespreking van multidissiplinêre deskundiges geakkommodeer kan word. ʼn Kwantitatiewe tegniek is nodig om die wisselwerking en dinamika van ʼn geheelboerderystelsel op ʼn gebruikersvriendelike en toepaslike manier te weerspieël. Multiperiode-begrotingsmodelle gee die vermoë om die kompleksiteit, wat met ʼn tipiese plaas geassosieer word, te akkommodeer deur die toepassing van basiese wiskundige en rekeningkundige beginsels. Die fisies-biologiese wisselwerking en struktuur van die plaas kan sodoende gemodelleer word, terwyl die finansiële prestasie van die kombinasies van verskillende besproeiing- en lowerbestuurstrategieë bepaal kan word. Die plaasvlakwinsgewendheid is veral sensitief vir die opbrengs en prys van produkte gelewer. Die behandelings wat die beste verwagte winsgewendheid getoon het, produseer teen ʼn relatiewe hoë produksie en prys en ’n relatiewe lae produksiekoste. Die oophanglowerbestuurbehandeling teen c. 60% en c. 30% plant beskikbare water-onttrekkingspeile is die mees en tweede mees winsgewende strategieë op per hektaar bruto marge en geheelplaasvlak. Die gebruik van scenario’s is geïnkorporeer om die impak van sleutelveranderlikes uit te wys en die vermoë van die model te illustreer. Sleutelfaktore tot die sukses wat aan sekere strategieë verbind word, kan sodoende uitgewys word. Deurgaans wys die resultate dat die balans tussen opbrengs, prys en produksiekoste belangriker is as die fokus op enige enkele een van die faktore.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2011. / Includes bibliography. / ABSTRACT: The grapevine must constantly find a balance between two continually changing environments, the rhizosphere (i.e. soil) and the troposphere (i.e. macroclimate). The adaptations are extremely complex because they encompass complicated and interrelated processes that are not yet fully understood. In terms of water-use behaviour, differences between cultivars have been described in the literature. In this study, the water status and stomatal conductance of four cultivars (Shiraz, Grenache, Pinot noir and Chardonnay) grafted onto R99 were studied. Diurnal cycles of water status and stomatal conductance, from 07:00 to 19:00, were followed for a single day at the end of the 2009 season. The results showed that, at the end of the season, Shiraz was subjected to water stress conditions, losing leaves and showing symptoms of berry shrivelling. The other three cultivars had a much better canopy status and no symptoms of berry shrivelling were observed. Based on the canopy observations and a comparison of the curves of stem water potential (Ψs) and stomatal conductance (gs), it seems that Pinot noir and Chardonnay are closer to the water-use behaviour of Grenache noir, which is known as a “pessimistic” cultivar, than to Shiraz, which is an “optimistic” cultivar. A study of four plots each of Chardonnay/101.14 Mgt and Shiraz/101.14 Mgt was carried out in eight commercial vineyards in the Robertson region in order to investigate the relationship between soil and root morphology, and the influence thereof on canopy development and berry growth. These plots had different soil types. Important soil properties are reported to limit root growth, individually or as a combination of restrictions. It was found that the size of the root system of 101.14 Mgt is defined by soil physical and chemical properties. The roots of 101.14 Mgt under irrigation can grow to a depth of 100 cm or beyond if the soil physical and chemical properties allow it. Because the soil properties define the root system and the water storage/drainage, they greatly influence the plant water status, even under irrigation. In an arid zone like Robertson, irrigation is an important management tool. The balance between canopy growth before véraison and the ability of the root-soil system to maintain that canopy size during the ripening process is crucial in an area with a high evaporative demand. In this regard, not all the soil properties-root system combinations showed satisfactory performance in maintaining the canopy functioning, which affected berry sugar loading and berry volume. In another study that is presented, forty soil profiles were characterised in the Robertson valley. The root systems were considered as a product of the soil properties, and thus the morphology of the root systems was used as a starting point to group soils together. The importance of soil depth has been described well, thus the root systems were first classified according to rooting depth – into shallow and deep root systems. The deep root systems were then subdivided, creating two subgroups of high root density and low root density. The two extreme groups (i.e. shallow roots, and deep roots with high root density) have particularly different soil properties. The soil characteristics found in these extremes are represented up to certain point by families of the South African soil taxonomy, mainly due to the restrictive function of the B horizon. This restrictive function is related to soil properties that are taken into consideration in the South African soil classification and that are important for grapevine root growth, as well as the thickness of the described horizons and the physical and chemical differences between the horizons. Soil properties have an important influence on root morphology. Due to the fundamental role played by the root system in the overall plant functioning, soil properties are of critical importance. In an arid area, the low water pressure in the atmosphere and the high temperature greatly affect the plant water status. The soil-root system combination plays an important role in the ability of the root system to supply the plant with water during times of high evaporative demand. Different cultivars will react differently due to differences in transpiration control. The maintenance of an adequate water status will have an immense influence on canopy development and maintenance, and on normal and steady berry ripening. In this study it was found that not all the soil-root combinations can fulfil this satisfactorily. Thus, the grapevine balance determined by the combination of the soil-root-canopy complex and the influence of management techniques is extremely important for the favouring of a good canopy:root system ratio, a functional canopy throughout the season and a steady berry ripening curve.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The topic of landscape heterogeneity has captured the imagination of ecologists and agriculturists alike and has been extensively investigated in this dissertation. Heuweltjies are landscape features putatively created by the termite Microhodotermes viator through their burrowing and nest-building activities. They have been closely examined in the natural veld of the Western Cape in the recent past and are the focus of many ecological studies. However, the effect of heuweltjies in cultivated landscapes (e.g. vineyards, orchards and wheat lands) remains unexplored. This study contributes significantly to our understanding of soil modifications associated with heuweltjies, as well as the physiology of vines growing on and off heuweltjies and wine made from these vines. It was hypothesized that heuweltjies occurring in cultivated areas can significantly affect crop yield and quality, thereby establishing itself as a potentially important role player in the agricultural economy of the Western Cape. This study was conducted in two climatic regions of the Western Cape, Stellenbosch (Mediterranean climate, Cabernet Sauvignon) and Robertson (semi-arid climate, Shiraz) to better understand how differences in heuweltjie characteristics correspond to differences in rainfall and temperature. In both study areas, heuweltjie soils were compared to non-heuweltjie soils with respect to physical and chemical. Grapevines associated with these heuweltjies were also compared to those growing on the adjacent, non-heuweltjie soils to determine any variation in vine vigour, physiology, phenology, berry characteristics and wine quality. Through the use of ANOVA's and Fisher's LSD posthoc tests to indicate statistical significance in soil and grapevine characteristics, it was apparent that heuweltjies induce substantial changes in soil and vine properties. Significant differences in the water content exist between the soils of the heuweltjies and non-heuweltjie areas. Heuweltjie soils exhibited higher values in comparison to the non-heuweltjie soils in the Stellenbosch study area, with opposite results in Robertson. Heuweltjie soils also displayed higher exchangeable calcium and magnesium and higher total carbon and total nitrogen values than non-heuweltjie soils in both study areas. Differences in physiology were more subtle, but vine vigour was severely altered on the heuweltjie-associated vines, exhibiting excessive vegetative growth in Stellenbosch, leading to variations in berry characteristics on and off the heuweltjies. Again, the opposite was observed for Robertson. Lower sugar and alcohol percentages and higher titratable as well as malic acid concentrations were observed in the wines emanating from the heuweltjies in Stellenbosch. Sensory analyses proved significant, as lower astringency and alcohol burn were detected in the Cabernet Sauvignon heuweltjie wines than the non-heuweltjie wines in the Stellenbosch study area. Chemical differences in the wines from the Robertson study are were insignificant. However, a significantly lower fruitiness was observed in the Shiraz heuweltjie-wines when compared to the non-heuweltjie wines. Differences in soil water content between heuweltjies and its adjacent soils was the most influential factor in this study, and affected all of the soil-grapevine interactions to a large extent. Further research need to be conducted to better understand and clarify the reasons behind these variations, as well as possible effects of global warming on heuweltjie functioning in different climatic regions of the Western Cape. / AFRIKAANSE OPSOMMING: Die onderwerp van landskap heterogeniteit het die verbeelding van beide ekoloë en landboukundiges aangegryp en is op `n omvangryke wyse ondersoek in hierdie tesis. Heuweltjies is landskap eienskappe geskep deur die uitgrawe en nesbou aktiwiteite van die termiet Microhodotermes viator. Heuweltjies in die natuurlike veld is intensief bestudeer in die onlangse verlede en is die fokus van `n verskeidenheid ekologiese studies. In bewerkte landskappe (bv. wingerde, vrugteboorde en koringlande) is daar egter `n groot tekort aan navorsing oor die invloed van heuweltjies. Hierdie studie dra grotendeels by tot ons begrip van heuweltjie-geassosieërde grondverandering, asook die fisiologie van wingerd wat groei op en af van heuweltjies, sowel as die wyn afkomstig van hierdie wingerdstokke. Hipoteties sal heuweltjies in bewerkte areas die gewasopbrengs asook –kwaliteit betekenisvol beïnvloed en word so dus gevestig as `n potensieël belangrike rolspeler in die landbou-ekonomie van die Wes-Kaap. Die studie was onderneem in twee klimaatstreke van die Wes-Kaap, Stellenbosch (Mediterreënse klimaat, Cabernet Sauvignon) en Robertson (semi-ariede klimaat, Shiraz) om vas te stel hoe verskille in heuweltjie eienskappe ooreenstem met verksille in reënval en temperatuur. In beide studie areas is heuweltjie gronde met nie-heuweltjie gronde vergelyk met betrekking tot fisiese en chemiese eienskappe. Wingerdstokke geassosieër met heuweltjies is ook vergelyk met dié wat heuweltjies omring om enige variasie in groeikrag, fisiologie, fenologie, druifkorrel eienskappe en wynkwaliteit te bepaal. Deur gebruik te maak van ANOVA's en Fisher se LSD posthoc toetse om statistiese betekenisvolheid in grond- en wingerdeienskappe aan te dui, was dit duidelik dat heuweltjies wesenlike veranderinge in dié eienskappe teweegbring. Betekenisvolle verskille heers in die waterinhoud tussen die heuweltjie en nie-heuweltjie gronde. Heuweltjie gronde het hoër waardes getoon in vergelyking met die nie-heuweltjie gronde in die Stellenbosch studie area, met teenoorgestelde bevindings in Robertson. Heuweltjie gronde het ook `n hoër konsentrasie uitruilbare kalsium en magenesium, en totale koolstof en stikstof in vergelyking met nie-heuweltjie gronde. Verskille in fisiologie was baie meer subtiel, maar wingerd groeikrag was beduidend verskillend op die heuweltjie-geasossieërde wingerdstokke, met oormatige vegetatiewe groei in Stellenbosch wat lei tot `n verskil in druifkorrel eienskappe op en af van die heuweltjie. Weereens is die teenoorgestelde waargeneem in Robertson. Laer suiker en alkohol persentasies, asook hoër titreerbare - en appelsuur konsentrasies was te bespeur in die wyne afkomstig van die heuweltjies in Stellenbosch. Sensoriese analise het betekenisvolle verskille bewys, met `n laer vrankheid en alkohol-brand sensasie waargeneem vir die Cabernet Sauvignon heuweltjie wyne as die nie-heuweltjie wyne in die Stellenbosch studie area. Chemiese verskille in die wyne vanaf Robertson was onbeduidend. Sensoriese analise het egter anders bewys, met `n betekenisvolle laer vrugtigheid te bespeur in die nie-heuweltjie wyne as die heuweltjie wyne in die Robertson studie area. Verskille in die grondwaterinhoud tussen heuweltjies en omringende gronde was die mees invloedryke faktor in hierdie studie en beïnvloed tot `n groot mate al die grond-wingerdstok interaksies. Verdere navorsing is nodig om helderheid te verskaf agter die redes vir hierdie variasies, sowel as moontlike gevolge van aardverwarming op funksionering van heuweltjies in verskillende klimaatstreke van die Wes-Kaap.

Thesis (MSc) -- Stellenbosch University, 2012. / ENGLISH ABSTRACT: One of the main objectives of the South African Wine of Origin Scheme (SAWOS) is to guarantee the quality of wine products emerging from South Africa’s viticultural production areas by preventing the abuse of names of products originating from outstanding viticultural areas. The study of terroirs contributes to knowledge that assists in delimiting potential viticultural areas in South Africa. Terroirs are areas with homogeneous groups of natural factors that, with the aid of effective management, have the potential to produce a unique product over a recognizable period. Natural terroir units (NTU) reflect the integration of relatively homogenous environmental factors, which include topography, climate, soil and geology. This study investigates the use of geographic information systems (GIS) and remote sensing methods in the identification of NTU in the Robertson wine district. Existing topographical, soil, geological and climatic GIS data layers were collected at various scales. In addition to this spatial data, orthorectified and radiometrically corrected SPOT 5 and ASTER satellite imagery were used to classify the land use/cover using an object-based image analysis (OBIA) approach. Eight land use/cover classes were distinguished by a sequential ruleset and an overall accuracy of 81.2% was achieved. The land use/cover layer was combined with the slope aspect and soil landscape to provide a three-component NTU description. One hundred and seventy NTU were identified, of which fifty five units exist for agriculture. These NTU can be used for site selection of agricultural produce and effective planning and management of land use. Climate was not included in the delimitation of NTU because the coarse resolution of climatic data could not be used to distinguish between different NTU. Therefore, all NTU identified in this research has similar climatic conditions. The major drawback of GIS-assisted terroir studies is the difficulty of representing a number of NTU on one GIS map. Therefore, it is recommended to associate the NTU map with a table of the classes instead. Furthermore, the accuracy, scale and resolution of available GIS data in South Africa influence the delimitation of NTU. Although remote sensing was found to provide efficient methods for land cover mapping, the use of multiseasonal satellite images would classify vineyards more efficiently because such an approach accounts for the different growth cycles of grapevines. / AFRIKAANSE OPSOMMING: Een van die hoof doelwitte van die Suid-Afrikaanse Wyn van Oorsprongskema (SAWOS) is om die kwaliteit van wynbouprodukte afkomstig van Suid-Afrikaanse wingerdbougebiede te verseker. Die studie van terroirs is geïdentifiseer as ‘n metode om moontlike wingerdbougebiede in Suid-Afrika af te baken. Terroirs is gebiede met relatief homogene natuurlike faktore wat oor ‘n erkenbare tydperk en met behulp van effektiewe bestuur die vermoë het om ‘n unieke produk te lewer. Dié natuurlike faktore word, “natuurlike terroir eenhede” (NTE) genoem en sluit topografie, klimaat, grond en geologie in. Hierdie navorsing ondersoek die gebruik van geografiese inligtingstelsels (GIS) en afstandswaarnemingstegnieke om NTE in die Robertson-wyndistrik te identifiseer. Bestaande ruimtelike topografiese-, grond-, geologiese- en klimaatdata is op ‘n verskeidenheid skale versamel. Bykomend tot hierdie ruimtelike data, is ortogekorrigeerde en radiometries-gekalibreerde SPOT 5 en ASTER satellietbeelde gebruik om landgebruik/ -bedekking te klassifiseer. Objekgerigte beeldanalise (OGBA) is toegepas tydens hierdie klassifikasie en agt landgebruik/ -bedekkingsklasse is onderskei deur gebruik te maak van ‘n stapsgewyse reëlstel. OGBA het ‘n algehele akkuraatheid van 81.2% gelewer. Die landgebruik/ -bedekkingsdata is gekombineer met hellingaspek en die grondlandskap om ‘n drieledige NTE-beskrywing te lewer. Een honderd en sewentig NTE is geïdentifiseer waarvan daar vyf-en-vyftig eenhede vir landbou bestaan. Hierdie NTE kan aangewend word vir die selektering van geskikte terreine vir landbou-gewasse en effektiewe grondgebruikbeplanning en -bestuur. As gevolg van die bestaande klimaatdata se growwe resolusie, was dit ongeskik om te onderskei tussen verskillende NTE. Dus heers daar soortgelyke klimaatstoestande vir elke NTE wat in hierdie navorsing geïdentifiseer is. Die grootste stremmende faktor wat GIS-verwante terroir navorsing beïnvloed, is die uitdaging om ‘n groot getal NTE op een kaart voor te stel. Daarom is dit beter om die NTE kaart met ‘n tabel te assosieer. Verder beïnvloed die akkuraatheid, skaal en resolusie van beskikbare digitale geografiese data in Suid-Afrika die afbakening van NTE. Alhoewel bevind is dat afstandwaarneming ‘n effektiewe metode is om landbedekking te karteer, sal die gebruik van meerseisoenale satellietbeelde wingerde meer doelmatig karteer omdat dit verskeie siklusse in die groei van wingerde in ag neem. SLEUTELWOORDE EN FRASES terroir, natuurlike terroir eenhede (NTE), geografiese inligtingstelsels, afstandwaarneming, wingerdkunde