The Namibian government introduced the Small Stock Marketing Scheme (SSMS) for the sheep market in 2004. The SSMS is a quantitative export restriction. Quantitative export restriction policies decrease the tradable quantity of a commodity, and increases domestic supply of a commodity, causing a lack of equilibrium in spatial markets. This, therefore, has the capacity to hinder market integration. Moreover, a quantitative export restriction disrupts the domestic supply and demand, and ultimately the equilibrium prices. A policy such as the quantitative export restriction therefore determines the domestic price levels. The effect of the SSMS on spatial market integration and price formation remains unclear. A lack of empirical evidence on spatial sheep market integration and domestic price levels can create challenges for policy makers. This is because a lack of evidence could prevent policy makers from implementing evidence-based policies, which might buffer poor consumers and producers from adverse price shocks, and lead to improved resource allocation. This study hypothesises that the SSMS policy negatively affected the long-run equilibrium relationship and short-run dynamics between the Namibian and South African markets. The study further hypothesises that the policy negatively influenced the level of equilibrium prices. As a result, this study hence observes spatial price integration in the presence of the SSMS, by defining the long-run equilibrium and short-run dynamics. The spatial price integration analysis is evaluated by subdividing price series data into pre-SSMS (1999M01-2003M12) and post-SSMS (2004M01-2015M12). The long-run equilibrium relationship is conducted with the Engle and Granger (1987) method and the Johansen (1988) cointegration approach. Short-run dynamics are, in turn, determined with an error correction model (ECM) and vector error correction model (VECM). The study also examined the impact of the SSMS on domestic price levels. This was done by recognising the reaction of the domestic supply, demand, and price functions to the SSMS. The analysis is conducted within the partial equilibrium framework (PEF). Additionally, the synthesis generated a simulation with the PEF to determine the impact on price changes were the SSMS to be removed. The analyses acknowledged a long-run equilibrium relationship between the spatial markets. As predicted, the long-run equilibrium relationship is not the same, pre- and post-SSMS. The price transmission elasticity (0.94) post-SSMS is marginally higher than pre-SSMS (0.88) is, which contradicts a priori expectation that quantitative export restrictions weaken price transmission. The pre-SSMS evaluation indicated a presence of short-run dynamics. Post-SSMS, the VECM revealed no bidirectional effect. The VECM also specified that the Namibian prices are effecting the adjustments in the short run to return to the long-run equilibrium position. This implies that if there is a shock that disturbs the equilibrium between the two spatial prices, Namibian prices would move to restore equilibrium. Likewise, the study appraised the response of the supply and demand functions to the policy in the PEF, incorporating the SSMS as an export ratio variable. The PEF results displayed that the SSMS influenced the supply function negatively, because of the negative elasticity of 0.013. This denotes that in the presences of the SSMS a 10 per cent increase in the quantitative export ratio decreases supply by 0.13 per cent, in which the response is slow. A negative effect is bound to decrease supply, and increase domestic price levels. Furthermore, the SSMS had a positive influence on the demand function, with an elasticity of 0.03 for the export abattoir demand, and 0.93 for the non-export abattoir demand. A positive impact on demand means a decrease in the producer price increases demanded for live sheep. The price equation outcome revealed that the SSMS had an insignificant effect of -0.0044 on the domestic producer prices. The price equation result is attributed to the low elasticity of the SSMS in the domestic supply and demand equation; the continued increase in producer prices post-SSMS due to the drought; and finally, because the SSMS is allowed to vary. Based on the simulation results, the removal of the SSMS policy would increase domestic producer prices by 4 per cent and 6 per cent, in 2017 and 2018, respectively. The percentage increase is considered low, as a result, this suggests that other dynamic factors, such as drought and market structure, affecting prices. This study therefore rejects the hypothesis stating that the long-run equilibrium relationship and short-run dynamic forces had reduced post-SSMS price transmission. The price transmission and speed of adjustment improved, post-SSMS. The study concludes that the SSMS policy did not have a detrimental effect, which was contrary to what was anticipated. The synthesis further fails to reject the hypothesis stating that the SSMS influenced domestic price levels, but the influence was very minimal and negligible. Both the spatial price integration and price formation analyses conclude that the SSMS had no detrimental effect on the sheep market. As a result, the study indicates that a quantitative export restriction policy, which varies, is better than an export control policy that does not allow any variation. / Dissertation (MSc (Agric))--University of Pretoria, 2017. / Agricultural Economics, Extension and Rural Development / MSc (Agric) / Unrestricted

Malawi is a predominantly agrarian economy, as the majority of the population is reliant on agriculture as their main source of livelihood. Despite that critical role the sector has to the economy, it has undergone minimal revolution to match its crucial status to the economy. There is need to understand the factors that have influenced agricultural policy decisions overtime. The quality of policy decisions taken over the last decade implies that, apart from economic motives, government has another agenda that it aims to achieve through some policy decisions. The government has manipulated the Farm Input Subsidy Programme (FISP) through populist pricing and implementation to uphold its popularity and legitimacy. Stakeholders and the citizenry need to ensure that their interests are included in agricultural policies. Mass media can play a crucial role in agricultural policy decisions. The media’s precise role in policymaking, however, has received little attention. This study aimed at establishing the influence of the media on agricultural policy decisions in Malawi, with a focus on the Farm Input Subsidy Programme (FISP). The study catalogued 853 articles, selected from two newspapers over a ten-year period (2005–2015). Malawi has implemented the subsidy programme for over a decade now to ensure food sufficiency. However, it is argued that the programme lacks direction and that it has been branded as a political tool for the ruling elites. The policy-makers have been criticised to the effect that the fertiliser policy is not motivated or driven by the technical efficiency required, but rather by the political incentives that are associated with the programme. The study adopted a political economy approach in establishing the role that the media has on agricultural policy. / Dissertation (MSc (Agric))--University of Pretoria, 2017. / Agricultural Economics, Extension and Rural Development / MSc (Agric) / Unrestricted

Between 75% and 90% of the world market for agricultural commodities is controlled by four major agribusiness multinationals (MNCs), namely Archer Daniels Midland (ADM), Bunge, Cargill and Louis Dreyfus Company (the ‘ABCD’ firms). The activities of the ABCD firms typically involve extensive cross-border trade and investment, which define internationalisation at a grand scale. The similarities in strategy and approaches of ABCD firms from an internationalisation perspective can be interpreted as a “convergence in practice” in the global agro-food system. However, the virtual absence of the ABCD firms in sub-Saharan Africa means that the continent remains the last frontier of global agro-food system convergence. In this sense, emerging agribusiness MNCs in sub-Saharan Africa represent a harbinger of global convergence in the continent’s agro-food sector. Yet there is limited understanding of the activities, strategies and approaches of these agribusiness MNCs. The objective of the study is to unpack agro-food system convergence within the context of agribusiness internationalization in sub-Saharan Africa. This task is achieved in four ways. First, the study shows evidence of convergence in sub-Saharan Africa through a trend analysis of four agribusiness MNCs within the continent. The analysis identifies similarities in strategy and approach between agribusiness MNCs in sub-Saharan Africa and ABCD firms. Second, the study assesses the cross-border market entry behavior of 67 agribusiness firms in the continent, including the four aforementioned firms that were used to illustrate evidence of convergence. Third, the study assesses the transboundary alliance behavior of 10 firms drawn from the same sample to show evidence of “corporate clustering” or cluster convergence. Fourth, the study takes a closer look into firm-level behavior through a specific case study of an internationalising agribusiness MNC in Zambia to show evidence of supplier convergence. Several research methods were used to analyse the various dimensions of convergence, all of which were examined within the framework agribusiness internationalisation. These methods include trend analyses to identify strategies and approaches, a multinomial logit model to assess cross-border entry strategies, game theory to assess the likelihood of transboundary strategic alliances and cluster convergence, and system dynamics modelling to analyse value chain integration and supplier convergence. The respective research methods were applied to a variable number of agribusiness firms which were drawn from the same sample. The study found evidence of convergence – defined by a gravitation of the agro-food system towards fewer large-sized agribusiness MNCs – which is being driven by two growth phenomena, namely, growth through value chain integration and growth through strategic alliances. The study identified these two types of convergence as follows: a) Supplier (?) convergence, which occurs when firms seek to gain competitive advantage in new markets by internalising critical but non-core value chain functions; and b) Cluster (?) convergence, which occurs when agribusiness MNCs leverage complementary assets of other competing firms and use collaborative advantage as a means to gain competitive advantage in new markets. The analysis predicts that there will be “a collapse of the middle”, which is defined by a gradual disappearance of agribusiness firms with an annual turnover ranging between US$160 million and US$996 million per annum, most of whom will enter into strategic alliances. Such strategic alliances are leading to a formation of large clusters that will likely morph into multi-billion-dollar agribusiness firms. It is entirely possible that these mega-agribusiness MNCs can ultimately be acquired by the powerful quartet of ABCD firms once the sub-Saharan African market matures, a phenomenon that will complete the final phase of global agro-food convergence. / Thesis (PhD)--University of Pretoria, 2018. / Agricultural Economics, Extension and Rural Development / PhD / Unrestricted

Semiclassical orthogonal polynomials are polynomials orthogonal with respect to semiclassical weights. The fascinating link between semiclassical orthogonal polynomials and discrete integrable equations can be traced back to the work of Shohat and Freud and later by Bonan and Nevai; orthogonal polynomials with Freud-type exponential weights have three-term recurrence coe cients that satisfy nonlinear second order difference equations. Fokas, Its and Kitaev identi ed these equations as discrete Painlev e equations. Magnus related the recurrence coe cients of orthogonal polynomials with respect to the Freud weight and classical solutions of the fourth Painlev e equation. We extend Magnus's results for Freud weight, by considering polynomials orthogonal with respect to a generalized Freud weight, by studying the theory of Painlev e equations. These generalized Freud polynomials arise from a symmetrization of semiclassical Laguerre polynomials. We prove that the coe cients in the three-term recurrence relation associated with a generalized Freud weight can be expressed in terms of Wronskians of parabolic cylinder functions that appear in the description of special function solutions of the fourth Painlev e equation. This closed form expression for the recurrence coe cients allows the investigation of certain properties of the generalized Freud polynomials. We obtain an explicit formulation for the generalized Freud polynomials in terms of the recurrence coe cients, investigate the higher order moments, as well as the Pearson equation satis ed by the generalized Freud weight. We also derive a second-order linear ordinary di erential equation and a di erential-di erence equation satis ed by the generalized Freud polynomials and we use the di erential equation to study some properties of the zeros of generalized Freud polynomials. Furthermore, we obtain limit relations for the recurrence coe cients of the generalized Freud polynomials using Freud's Kunstgri method. We verify the existence of an asymptotic series for the recurrence coe cient using an extension of the result by Bleher and Its [17] and we provide an asymptotic expansion for the recurrence coe cients of the three-term recurrence relation satis ed by monic generalized Freud polynomials. / Thesis (PhD)--University of Pretoria, 2018. / Mathematics and Applied Mathematics / PhD / Unrestricted

The degradation of hemicellulose is a vital step in the efficient utilisation of plant biomass, an abundant source of carbohydrates in nature. Xylan, the most prevalent hemicellulose, is digested by xylanases and much work has gone into improving the efficiency and stability of these enzymes. Interest has recently shifted to non-catalytic, accessory domains found in many xylanases, including carbohydrate binding modules (CBMs). CBMs may enhance enzyme properties, such as thermostability and efficiency. This effect has, however, not yet been fully explained. In this study, a novel multimodular xylanase isolated from the hindgut metagenome of the snouted harvester termite (Trinervitermes trinervoides) was characterised and the properties of its two identical CBMs analysed. Xylanase variants were produced in E. coli by deleting none, one or both CBMs. The variants were functionally characterised using a modified DNS assay in a thermocycler and structurally modelled using computational techniques. Deleting one CBM shifted the pH profile, slightly increasing activity at lower pH whereas removing both CBMs decreased activity at 60°C from 90% (SD = 1.3) to 56% (SD = 2.9). Removal of the CBMs did not statistically significantly affect the Michaelis constants (KM), but did reduce the turnover number (kcat). Structure modelling failed to accurately predict the structure of the complete enzyme and in particular any interactions between domains. The origin of the stabilising effect of the second CBM and hence the evolutionary benefit of two CBMs remains unresolved. / Dissertation (MSc)--University of Pretoria, 2017. / Biochemistry / MSc / Unrestricted

In this dissertation, we t various nancial models to observed stock prices and we calculate the option prices under each of these models. All of the models considered are based on Lévy processes, which are processes with independent and identically distributed increments. The processes are popular in nance due to their exibility and their desirable mathematical properties. The models considered include the celebrated Black-Scholes model, under which the log-retuns are assumed to be driven by a Brownian motion. Two other classes of models are included in this study, both of which are generalizations of the Black-Scholes model. The rst class is the geometric Lévy process models, of which the Black-Scholes is a special case. Two speci c examples within this class are considered, the two models use the normal inverse Gaussian and Meixner processes to model log-returns. The second class of model considered generalizes the Black-Scholes while modeling the passing of time using an increasing stochastic process. The two speci c examples considered models time using a Pareto and a lognormal process. The aim of this dissertation is to explore the question of which model to use in a given nancial market. To this end, we t each of the models considered to observed log-returns. Following this step we calculate the prices of options available in this market. This is done in order to compare the prices calculated under the models to the prices observed in the market. In each case the Esscher transform is used in order to calculate the equivalent martingale measure used for the calculation of the option prices. Note that this is not the approach typically employed by nancial practitioners. In practice these models are often calibrated to the observed option prices, meaning that the parameters of the models are chosen so as to minimise some distance measure between the observed and calculated option prices. In this dissertation we depart from this methodology in order to determine if the models tted to the stock prices are capable of producing realistic option prices. When analysing the results obtained we use a two fold approach. The rst step is to determine which of the models considered provides the best t to the observed log-returns (this is done by comparing the integrated squared errors between the resulting densities and a kernel density estimate), and the second step is to compare the calculated and observed option prices (using the root mean square error calculated between the two sets of option prices). We conclude that, surprisingly, the model that ts the stock price data best often does not provide an adequate t to the option prices, and vice versa. / Dissertation (MSc)--University of Pretoria, 2017. / Statistics / MSc / Unrestricted

Adequate knowledge of the regional subsurface geometry depth relationship between the limbs and distribution of mineral zones within the Rustenburg Layered Suite (RLS) is required for better understanding of the emplacement geometry, distribution of economic mineral zones and structural evolutionary issues. This will lead to improved exploration prospects that could assist in less degradation mining activities and environmental hazard control and management. Incompleteness of surface outcrops and limited availability of seismic data has been a hindrance to this. This research focused on the determination from available borehole data, the geometry and depth relations to modern topography of the RLS. Extensive Geostatistical analysis of hundreds of borehole log data was carried out to better constrain the complex geologic structural framework and architecture of the RLS. This has helped to identify and visualize the subsurface stratigraphic units, their geometric forms and improved the understanding of the geology and structure of the RLS. / Thesis (PhD)--University of Pretoria, 2015. / Geology / PhD / Unrestricted

Nitrogen (N) plays a vital role in plant metabolic processes, and may cause severe economic losses in crop production if deficient. When agricultural composts are used to counteract soil impoverishment and supply crop nutrients, it is crucial to understand the dynamics of nitrogenous compounds to optimize N uptake. Five major soil groups of Mauritius were amended with three types of compost, filtercake (FC), poultry litter (PL), and poultry manure-sugarcane thrash (PM), at application rates to supply 140 kg N ha-1in a laboratory incubation experiment over 215 days. In each soil group, only specific types of agricultural composts resulted in a statistically significant (P < 0.05) increase in cumulative N mineralized, relative to the control: PM in the Low Humic Latosol (L), PM and PL in the Humic Latosol (H), PL in the Humic Ferruginous Latosol (F), PL in the Latosolic Reddish Prairie (P) group, and FC and PL in the Latosolic Brown Forest (B) group. In general, the N-NO3- form was dominant in all the treatments across the soil groups. Only in the H soil amended with PM and PL was the N-NH4+ form pre-dominant. The index of N availability, N0k, showed that in control soils, the daily N availability (mg N kg-1 soil day-1) was in the order B (1.242) > H (0.975) > F (0.674) > P (0.637) > L (0.524). The relatively high N availability in the B may explain why sugarcane cultivated in this soil islowly responsive to increments in N fertilizers. Relative to the control soils, FC resulted in a decrease in N availability, mostly due to a relatively slower rate of N mineralization. Poultry litter compost increased daily N availability in all the soil groups. Increased N availability was also noted in all soils amended with PM, except in the P soil. In general, the percentage of organic N mineralization in control soils varied from 2% to 4%. In FC-amended soils, between 2% and 5% of the organic N from soil and compost mineralized. Applied in the weathered soil groups (H, L and F), PM resulted in an appreciable increase in organic N mineralized that varied between 6% and 9%. However, in the immature soil, PM had a relatively mitigated effect, with 1% of total N mineralization in the amended P soil, and 3% in the B soil. Across the soil groups amended with PL, from 4% to 8% of the total soil and compost organic N mineralized. / Dissertation (MSc (Agric))--University of Pretoria, 2017. / Plant Production and Soil Science / MSc (Agric) / Unrestricted

This study was conducted to better understand the usefulness of water footprint (WF) information for vegetable crops produced on a water-stressed aquifer in South Africa. Different methodologies were investigated in a literature review and the methodologies proposed by the Water Footprint Network (WFN), the Life Cycle Assessment (LCA) communities, and the hydrological-based WF community were selected for a case study on the cultivation of carrots (Daucus carota), beetroot (Beta vulgaris), cabbage and broccoli (Brassica oleracea), lettuce (Lactuca sativa), maize (Zea mays) and wheat (Triticum aestivum) on the Steenkoppies Aquifer, Gauteng, South Africa. A key aim was to identify one or more simple yet effective WF method(s) that can be applied in South Africa to improve water resource management and for raising consumer awareness. The case study on the Steenkoppies Aquifer indicated that WF metrics from the three methodologies differed notably. For example, an annual two-crop rotation sequence (carrots in summer and cabbage in winter) had an average blue WF of 57 m3 tonne-1 according to the WFN methodology, compared to 32 and 44 m3 tonne-1 according to the hydrological-based method and the LCA methodology, respectively. Estimated WFs differed notably between different crops and growing seasons, for example, according to the WFN methodology the blue plus green WFs of lettuce in summer was 56 m3 tonne-1, compared to 327 m3 tonne-1 for the blue plus green WF of broccoli in winter. The WFN methodology consists of goals and scoping phase, an accounting phase, determining the volume of water required to produce a product, followed by a sustainability assessment, which interprets the impact of the WF in the local context of water availability. Finally, a suitable response is formulated. The WFs according to the WFN methodology is not considered to be suitable for awareness raising if it is communicated without the sustainability assessment or outside the local environmental context of the water use. As an alternative, the LCA-based WF methodologies have been developed to incorporate the environmental sustainability in the WF assessments, and represent a stress weighted index of water use, which can be used together with other LCA metrics. Also, a hydrological-based methodology has been proposed and developed to incorporate all the water flows and other aspects of the hydrological system, so the WFs can be reported as a stand-alone value. While the latter two methodologies aimed to develop single WF values that indicate the sustainability of a water use, due to the vast number of variables, complexities and trade-offs involved in sustainable water use, obtaining such a number still does not seem possible at this stage. Following this comparison, the WFN method was selected as the key methodology for this research project for reasons that include the following: • The methodology is simple and well-developed. • The WFs are based on actual water volumes used for a product, a process or by an entity, which can potentially be used in different information systems, such as water use licensing, up-scaling to a catchment level, and quantifying water consumed by different users for allocation purposes. • By using different functional units, such as nutritional value and economic gain, the volume of water can be directly linked to certain benefits derived from the product. • The volumetric WFs can reveal impacts on water resources in different seasons of a hydrological or calendar year. • It can indicate high WFs of certain crop species, such as broccoli, or certain growing regions, such as those which experience relatively high vapour pressure deficits or with poor soils. • It allows for local geographic contextualisation if there is suitable information to conduct the sustainability assessment. Despite the relative simplicity of the WFN methodology, some complexities were encountered in its application for quantification of WFs of selected vegetable crops on the Steenkoppies Aquifer. In this study, we assessed that WF outcomes are influenced by several factors, including natural variations in weather conditions between growing seasons and between different years. Therefore, WFs should be site specific and calculated for a particular season or year. Water footprints are also directly dependent on crop simulation model outputs, which are in turn affected by the quality of parameterisation and input data used. Whether solar radiation (Rs) data was measured or estimated were found to have a notable impact on estimates of crop reference evapotranspiration (ETo) and crop yields in summer season. It was recommended that if estimated data for a specific weather variable is used for crop parameterisation, the same type of data be used when simulations are executed with those crop parameters (assuming that the variation in the error in Rs will be consistent for a crop calibrated in summer or winter and simulated in the same season). The error in Rs estimates was, however, not consistent over different seasons and parameters generated for crop in a particular season should be used cautiously for other seasons. Variations in water content between different crops can impact the WFs, which are most commonly expressed as a volume of water (e.g. in m3) used per unit of yield (e.g. in tonnes) in fresh mass. This resulted in relatively higher WFs for grain crops with low moisture contents, when using yields in fresh mass. For example, alternative functional units, such as nutritional content (such as zinc or iron) or economic gain are proposed to be used to link the WFs to a more specific potential benefit, which makes comparisons possible. Packhouse WFs were calculated to quantify the volume of water used in cleaning and/or packaging a unit yield of carrots, cabbage and lettuce in a packhouse on the Steenkoppies Aquifer according to the WFN methodology. As observed in previous studies, packhouse blue WFs were relatively low compared to the WFs linked to the cultivation phase (ET) (2.2% of the total field to farm gate WF for carrots, 0.5% for cabbage and 1.5% for lettuce). This highlights the importance of water use during cultivation, as compared to the rest of the supply chain, when considering measures to reduce water use impacts on the aquifer. Using phosphorus (P) as the critical pollutant, packhouse grey WFs were estimated to be considerably larger than the packhouse blue WFs. For carrots, cabbage and lettuce, packhouse grey WFs were 44, 12 and 16%, respectively, of the grey WF linked to the cultivation of these crops. The inclusion of recycling and filtration systems, final fate of the disposed water and associated pollutants, and assimilation capacity of the natural environment make the estimation and interpretation of grey WFs challenging! Grey WF assessments, which were not validated by the Steenkoppies Aquifer water quality measurements, require further research and refinement. / Thesis (PhD)--University of Pretoria, 2017. / Plant Production and Soil Science / PhD / Unrestricted

In South Africa, Nguni cattle are one of the breeds found predominantly in extensive production systems. In this study the effect of two feedlot diets with different energy levels have been investigated using a transcriptome approach. Twenty Nguni and twenty Bonsmara bulls were fed a low or a high energy diet for 120 days and growth parameters were measured. At slaughter, L. dorsi muscle samples were collected for transcriptome analysis. Performance results showed a higher live weight, carcass weight and marbling score for all bulls fed the high energy diet compared to bulls fed the low energy diet. Diet had a greater effect on the Bonsmara compared to the Nguni according to transcriptomic and phenotypic values. A total of 73 differentially expressed genes were observed between the diets across breeds. The genes that were involved in intramuscular fat deposition (CRHR2, NR4A3, MMD) were expressed on a higher level in the bulls on the low energy diet compared to bulls on the high energy diet. Genes that were involved in muscle deposition (PITX2, Leptin, AVP) was expressed higher in the bulls on the high energy diet. Comparing the breeds revealed that 2214 genes were differentially expressed between the Bonsmara and the Nguni. At the end of the feedlot trial a higher expression of marbling genes (SIRT, ND, ADIPOQ) were observed in the Nguni, however this expression was not observed in the marbling scores recorded. Several genes (ASIP, MOGAT, SNAI3) that were involved in fat deposition were upregulated in the Bonsmara. This suggests that the Nguni was still growing at the end of the feedlot trial while the Bonsmara had reached physiological maturity. An extended feedlot period for Nguni cattle should be considered in future studies. This study provides reference data for differentially expressed genes in muscle of South African feedlot cattle. / Dissertation (MSc (Agric))--University of Pretoria, 2018. / Animal and Wildlife Sciences / MSc (Agric) / Unrestricted