Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Profitability in the export driven South African blueberry industry is dependent on early spring harvests. The George region in the Western Cape accumulates too few chill-units to release buds of some southern highbush (SHB) blueberry cultivars from endodormancy. This causes problems like delayed budbreak and extended harvests. Growers of other temperate fruit crops are also affected by these problems and chemical rest breaking agents (RBAs) are applied in orchards in an attempt to overcome these. Application of the RBA hydrogen cyanamide (HC) occurs commonly in commercial pome and stone fruit orchards while thidiazuron (TDZ), another RBA is applied on a limited scale in apple orchards. The effect of RBA application on berry ripening, berry size and yield in SHB cultivars Bluecrisp, Emerald and Star was investigated for two seasons in an orchard near George, in order to determine to what extent harvest scheduling with RBAs is possible. Following Dormex® (HC, 520 g L-1) application during 2010, when a warm winter was experienced, the berry ripening of ‘Bluecrisp’ was accelerated. Dormex® application before reproductive bud scales opened, but after some chilling, resulted in acceptable yield and berry size without damage to reproductive buds. A 1% rate gave similar results as a 2% rate, but at a lower risk of reproductive bud damage. Lift® (TDZ, 3 g L-1) application reduced the number of days to 75% harvest in ‘Star’ during 2010. Lower yielding plants produced larger berries than those from higher yielding plants. Lift® application after reproductive buds scales have opened caused malformed and damaged flowers. Delaying the initiation of reproductive buds could delay spring reproductive budbreak until after new leaves had formed. In turn, this should induce a faster berry ripening rate in some SHB cultivars than would otherwise be the case following unseasonably warm winters. Reproductive bud initiation in SHB blueberries occurs under long (16 hours) nights with the mediation of phytochrome. It is possible in a controlled environment to suppress SHB blueberry reproductive bud initiation by night interruption (NI). The effect of NI on berry ripening, berry size and yield in ‘Emerald’ and ‘Snowchaser’ was investigated for two seasons, to determine what degree of harvest scheduling is possible with this technique. NI did not suppress reproductive bud development under these trial conditions, since both cultivars flowered and produced fruit. The effect on berry size and yield was cultivar specific. During 2011 NI decreased the number of berries harvested and total yield per plant in ‘Emerald’, and this decrease was linear the longer the NI lasted. / AFRIKAANSE OPSOMMING: Winsgewendheid in die uitvoer-gedrewe Suid-Afrikaanse bloubessie-bedryf is van vroeë lente oeste afhanklik. In die George-omgewing in die Wes-Kaap bou te min winterkoue op om die endodormansie van sommige ‘southern highbush’ (SHB) bloubessie kultivars natuurlik op te hef, wat probleme soos vertraagde bot en uitgerekte oestye veroorsaak. Produsente van ander gematigde vrugtesoorte, word ook deur hierdie probleme geraak en chemiese rusbreekmiddels (RBs) word in boorde aangewend in ’n poging om dit te oorkom. In kern- en steenvrugboorde vind aanwending van die RB waterstofsianamied (WS) algemeen plaas. Thidiazuron (TDZ), ’n ander RB word op beperkte skaal in appelboorde aangewend. Die uitwerking van RBs op bessierypwording, -grootte en opbrengs van SHB kultivars Bluecrisp, Emerald en Star is oor twee seisoene in ’n boord naby George ondersoek, om vas te stel tot watter mate bloubessie-oesskedulering met behulp van RB aanwending moontlik is. Na Dormex® (WS, 520 g L-1) aanwending in 2010, waarin ’n warm winter ondervind is, is die bessierypwording van ‘Bluecrisp’ versnel. Dormex® aanwendingstye voordat blomknopskubblare oopmaak, maar nadat winterkoue opgebou het, het ’n aanvaarbare opbrengs en bessiegrootte met geen blomknopskade tot gevolg gehad nie. ’n 1% Konsentrasie gee soortgelyke reaksies as ’n 2% aanwending maar teen ’n laer risiko vir blomknopskade. Lift® (TDZ, 3 g L-1) aanwending het die aantal dae tot 75% oesinsameling van ‘Star’ in 2010 verminder. Plante wat ’n laer opbrengs lewer produseer groter bessies as die wat ’n hoër opbrengs lewer. Lift® aanwending nadat blomknopskubblare oopgemaak het, het misvormde en beskadigde blomme tot gevolg gehad. Vertraging van blomknopinisiasie kan die oopmaak van blomknoppe uitstel tot na nuwe blare in die lente gevorm het. Dit kan vinniger bessie rypwording meebring as wat die geval vir sommige SHB kultivars na warm winters is. Die aanvang van blomknopontwikkeling in SHB bloubessies vind tydens lang nagte (16 ure) plaas en staan onder beheer van fitochroom. Onder beheerde toestande kan bloubessie blomknopinisiasie deur onderbreking van die lang donker (nag) tydperk (ON) in ’n lig-donker siklus onderdruk word. Die uitwerking van ON op bessierypwording, -grootte en opbrengs van ‘Emerald’ en ‘Snowchaser’ is oor twee seisoene ondersoek, om die mate waartoe oesskedulering met hierdie tegniek in ’n boord moontlik is aan te spreek. ON het nie die blomknopinisiasie onder hierdie eksperimentele toestande onderdruk nie, aangesien beide kultivars in albei seisoene kon blom en opbrengste lewer. Die effek op bessiegrootte en opbrengs was kultivar spesifiek. In 2011 is die totale opbrengs en hoeveelheid bessies per plant geoes van ‘Emerald’, deur ON verminder en dié vermindering was liniêr met toename in aantal ON siklusse.

Thesis (PhD (Logistics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Computerised sugarcane harvest scheduling decision support is an active fi eld of research which ties in closely with the broader problem of automating and streamlining the various activities in the sugar supply chain. In this dissertation, the problem of providing decision support with respect to sugarcane harvesting decisions is defined within a number of contexts, each representing a typical kind of organisation of sugarcane farmers into a cohesive decision making unit with its speci fic requirements and limitations that exist in practice. A number of variations relevant to these contexts of an overarching tactical sugarcane harvest scheduling problem (THSP) are considered and solved in this dissertation. The THSP is the problem of providing objective, responsible decision support to persons charged with the task of determining optimal harvesting dates for a set of sugarcane fields across an entire season. Sugarcane fields typically diff er in terms of the age, variety, life-cycle stage and in many other properties of the cane grown on them. The growth of sugarcane crops may also be a ffected by environmental conditions such as accidental fires, frosts or storms which have a detrimental e ffect on crop-value. Since sugarcane is a living organism, its properties change over time, an so does the potential pro t associated with it. The practicalities of farming cause further complication of the problem (for example, seasonal changes alter the conditions under which the crop is harvested and transported). The rainy season carries with it the added cost of disallowing long-range vehicles to drive into the fields, forcing the unloading and reloading of cane at so-called loading zones. Other considerations, such as the early ploughing out of fields to allow them to fallow before being replanted, compounds the THSP into a multi-faceted difficult problem requiring efficient data management, mathematical modelling expertise and efficient computational work. In the literature the THSP has been viewed from many different standpoints and within many contexts, and a variety of operations research methodologies have been employed in solving the problem in part. There is, however, no description in the literature of a solution to the THSP that takes the negative e ffects of extreme environmental conditions on the quality of a harvesting schedule into account in a scienti fically justifi able manner; most models in the literature are based on optimising sucrose yield alone under normal conditions, rendering weak schedules in practice. The scope of the modelling and solution methodologies employed in this dissertation towards solving the THSP is restricted to integer programming formulations and approximate solution methods. The parameters associated with these models were determined empirically using historical data, as well as previous work on deterioration of sugarcane following environmental and other events. The THSP is solved in this dissertation by designing a generic architecture for a conceptual decision support system (DSS) for the THSP in the various contexts referred to above, which is capable of accommodating the e ects of extra-ordinary environmental conditions, as well as the introduction of a computer-implemented version of a real DSS for the THSP conforming to the framework of this generic architecture. The DSS building blocks include prediction models for sugarcane yield, sugarcane recoverable value under normal circumstances, the costs associated with a harvesting schedule and the negative e ects on sugarcane recoverable value of extraordinary environmental conditions. The working of the DSS is based on a combinatorial optimisation model resembling the well-known asymmetric traveling salesman problem with time-dependent costs which is solved approximately by means of an attribute-based tabu search in which both local and global moves have been incorporated. The DSS is also validated by experienced sugarcane industry experts in terms of the practicality and quality of the schedules that it produces. / AFRIKAANSE OPSOMMING: Gerekenariseerde besluitsteun vir die skedulering van suikerriet-oeste is 'n aktiewe navorsingsveld wat nou verwant is aan die bre ër probleem van die outomatisering en vaartbelyning van 'n verskeidenheid aktiwiteite in die suikervoorsieningsketting. Die probleem van die daarstelling van steun rakende suikkerriet oestingsbesluite word in hierdie proefskrif in 'n aantal kontekste oorweeg, elk met betrekking tot 'n tipiese soort organisasie van suikerrietboere in 'n samehorige besluitnemingseenheid met sy spesi eke vereistes en beperkings in die praktyk. Verskeie variasies van 'n oorkoepelende taktiese suikerriet-oesskeduleringsprobleem (TSOSP) wat in hierde kontekste relevant is, naamlik die probleem om objektiewe, verantwoordbare steun aan besluitnemers te bied wat verantwoordelik is vir die bepaling van optimale oesdatums vir 'n versameling suikerrietplantasies oor die bestek van 'n hele seisoen, word in hierdie proefskrif bestudeer en opgelos. Suikerrietplantasies verskil tipies in terme van ouderdom, gewastipe, posisie in die lewensiklus, en vele ander eienskappe van die suikerriet wat daar groei. Omgewingstoestande, soos onbeplande brande, ryp of storms, het verder ook 'n negatiewe impak op die waarde van suikerriet op sulke plantasies. Omdat suikerriet 'n lewende organisme is, verander die eienskappe daarvan oor tyd, en so ook die potensi ele wins wat daarmee geassosieer word. Boerderypraktyke bemoeilik verder die skeduleringsprobleem onder beskouing (seisoenale veranderings beïnvloed byvoorbeeld die wyse waarop suikerriet ge-oes en vervoer word). Addisionele koste gaan voorts met die re ënseisoen gepaard, omdat die plantasies dan nie toeganklik is vir langafstand transportvoertuie nie en suikerriet gevolglik na spesiale laaisones gekarwei moet word voordat dit op hierdie voertuie gelaai kan word. Ander oorwegings, soos die vroe ë uitploeg van plantasies sodat die grond kan rus voordat nuwe suikerriet aangeplant word, veroorsaak dat die TSOSP 'n moeilike multi-faset probleem is, wat goeie databestuur, wiskundige modelleringsvernuf en doeltreff ende rekenaarwerk vereis. Die TSOSP word in die literatuur vanuit verskillende standpunte en in verskeie kontekste oorweeg, en 'n aantal uiteenlopende operasionele navorsingsmetodologie ë is al ingespan om hierdie probleem ten dele op te los. Daar is egter geen poging in die literatuur om 'n oplossing vir die TSOSP daar te stel waarin daar op 'n wetenskaplik-verantwoordbare wyse voorsiening gemaak word vir die negatiewe e ffekte wat uitsonderlike omgewingstoestande op die kwaliteit van oesskedules het nie; die meeste modelle in die literatuure is op slegs sukrose-opbrengs onder normale omstandighede gebaseer, wat lei na swak skedules in die praktyk. Die bestek van die wiskundige modellerings- en gepaardgaande oplossings-metodologie ë word in hierdie proefskrif vir die TSOSP beperk tot onderskeidelik heeltallige programmeringsformulerings en die bepaling van benaderde oplossings deur lokale soekprosedures. Die parameters wat met hierdie modelle en soekmetodes geassosieer word, word empiries bepaal deur gebruikmaking van historiese data asook bestaande werk oor die degradering van suikerriet as gevolg van omgewings- en ander eksterne faktore. Die TSOSP word in hierdie proefskrif opgelos deur die ontwerp van 'n generiese argitektuur vir 'n konseptuele besluitsteunstelsel (BSS) vir die TSOSP in die onderskeie kontekste waarna hierbo verwys word en wat die e ekte van uitsonderlike omgewingsfaktore in ag neem, asook die daarstelling van 'n rekenaar-ge ïmplementeerde weergawe van 'n daadwerklike BSS vir die TSOSP wat in die raamwerk van hierdie generiese argitektuur pas. Die boustene van hierdie BSS sluit modelle in vir die voorspelling van suikerrietopbrengs, die herwinbare waarde van suikerriet onder normale omstandighede, die verwagte koste geassosieer met 'n oesskedule en die negatiewe e ekte van omgewingsfaktore op die herwinbare waarde van suikerriet. Die werking van die BSS is gebaseer op 'n kombinatoriese optimeringsprobleem wat aan die welbekende asimmetriese handelreisigersprobleem met tyd-afhanklike kostes herinner, en hierdie model word benaderd opgelos deur middel van 'n eienskap-gebaseerde tabu-soektog waarin beide lokale en globale skuiwe ge ïnkorporeer is. Die BSS word ook gevalideer in terme van die haalbaarheid en kwaliteit van die skedules wat dit oplewer, soos geassesseer deur ervare kundiges in die suikerrietbedryf.

The goal of harvest scheduling is to produce a practical operations schedule that can be implemented in the field by operational foresters and maximizes all values. The resulting harvest units need to represent a close approximation to what will be done operationally and while emulating natural disturbance regimes and topographic boundaries. using flow direction surfaces. Two methods of meeting spatially acceptable harvest units through a heuristic algorithm and a mixed integer programming method. A factor analysis was conducted on both to determine the statistical significance between 3 forest characterizations and mean financial and shape index indicators. Mixed integer programming had higher cash flows and net present values per hectare and the heuristic method had higher net present value per cubic meter at the 95% level of significance.

Ce projet de recherche a été réalisé avec la collaboration de FPInnovations. Une part des travaux concernant le problème de récolte chilien a été effectuée à l'Instituto Sistemas Complejos de Ingeniería (ISCI) à Santiago (Chili). / La planification de la récolte forestière comporte différents niveaux de planification selon l'horizon de temps du problème et la nature des décisions à prendre. Dans un premier temps, nous nous intéressons à un problème de planification annuelle de la récolte, à mi-chemin entre la planification tactique et opérationnelle. Ce problème appliqué à l'exploitation forestière au Québec, naît d'un besoin de l'industrie québécoise d'un outil pour la planification annuelle intégrée qui fournit aux équipes de récolte leur calendrier. L'intégration consiste à déterminer les affectations des équipes aux blocs en fonction des besoins des usines, et qui respectent les contraintes de transport, de gestion des stocks, et bien entendu les conditions d'exploitation en forêt. Plusieurs modèles de types MIP ont été formulés, des approches de résolution adaptées à la structure de chacun des modèles ont été développées. L'approche par horizon roulant est celle dont les résultats surpassent les deux autres et surtout, améliorent de façon significative les plans usuellement suivis, notamment en réduisant les volumes non livrés aux usines de moitié, ou encore en divisant entre 2 et 6 fois les volumes en stock quand la demande diminue. De plus, le développement d'une interface pour systématiser le processus de résolution et élargir le nombre d'utilisateurs, est la seconde contribution de la thèse. Cette étape du projet correspond à un transfert de technologie de l'université vers l'industrie. Le second problème de planification se situe au Chili, est une planification tactique de la récolte dirigée par les prix et demandes en produits finis, ces derniers étant considérés comme des paramètres aléatoires. Le problème stochastique formulé est résolu suivant une méthode de décomposition par scénarios dont le nombre varie entre 10 et 100. Pour chaque scénario, la solution déterministe, lorsqu'elle est réalisable, est comparée avec celle issue de la résolution du problème stochastique. La solution déterministe n'est réalisable que pour une dizaine de scénarios parmi 100, et les pertes encourues sont en moyenne de 9%. / Harvest planning has different levels according to the time horizon of the problem and the nature of the decisions to be taken. Initially, we are interested in an annual harvest scheduling problem, halfway between tactical and operational planning. This problem applied in Qu\'ebec, is motivated by a need from the industry for an integrated tool that provides annual schedules to harvest teams. The integration is to determine demand driven assignments of teams to cutblocks and to manage transportation and inventory accordingly. Several MIP models have been formulated, and three solution approaches have been developed according to the structure of each model. The rolling horizon approach performs better than the other two, by improving significantly from the traditional harvest plan, especially by reducing by half non delivered volumes or by dividing between 2 and 6 times volumes in storage when demands decrease. Another contribution of the thesis is the creation of an interface to systematize solution process and to allow other users. This is the object of a transfer project between academics and industry. The second problem is a Chilean tactical harvest planning. Harvesting decisions are driven by stochastic demands and prices of final products. The stochastic problem is solved using a heuristic based on a scenario decomposition technique. The number of scenarios considered is between 10 and 100 scenarios. For each scenario, when the deterministic solution is feasible, it is compared with the stochastic solution for the current scenario. The deterministic solution is only feasible for 10% of the scenarios, and induces losses of 9% in average.