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Masters Degrees (Agricultural Engineering)

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    Developing integrated climate change adaptation strategies using the water-energy-food nexus approach: a case study of the Buffalo River catchment, South Africa.
    (2023) Dlamini, Nosipho.; Senzanje, Aidan.; Mabhaudhi, Tafadzwanashe.
    South Africa’s climate has high spatial and temporal variability. Literature on historical rainfall patterns shows substantial declines in rainfall across the country, except in south-western South Africa, which displays increasing trends. Under the Representative Concentration Pathways (RCPs) 4.5 and 8.5 scenarios, statistically downscaled rainfall projections show different patterns across South Africa throughout the 21st century. Literature indicates that this uncertainty will majorly impact South Africa’s surface water availability as its main input variable is rainfall; hence, all possible outcomes need to be planned for. Planning should include the energy and food production sectors as they primarily depend on the water sector. The Buffalo River catchment, situated in the northern parts of KwaZulu-Natal, South Africa, is a high rainfall receiving area, with a mean annual precipitation of 802 mm. Despite its abundant rainfall, the catchment has had its fair share of droughts, significantly impacting livelihoods and socio-economic activities. Recent reports indicate that the Buffalo River catchment’s surface water storage facilities are insufficient to meet the population’s demands by 2050. A detailed water resources assessment is required to confirm and quantify the possible alterations that climate change could cause to the catchment’s hydrology before any actions can be taken, especially regarding increasing the water storage capacity of the catchment. As such, this study aims to investigate and assess the impacts of climate change on the Buffalo River catchment’s surface water availability and reliability of water resources in meeting projected water demands, with a specific focus on agricultural and energy generation water demands. Furthermore, the study aims to develop integrated water resources adaptation strategies to increase water, energy and food security within the catchment. Due to its transdisciplinary nature, the Water-Energy-Food (WEF) nexus methodology was used as an analytical tool to carry out the research’s objectives. The study was based on the null hypotheses of climate change not varying surface water availability and reliability, and that the optimized CC water management strategies will not yield any improvements in merging potential gaps between water supply and demands. Study findings indicate that the Buffalo River catchment is anticipated to receive increases in precipitation magnitude and fluctuations throughout the 21st century. However, the increases in surface water availability that result from the anticipated rainfall increases are insufficient and unreliable to meet the rise in demands for water within the catchment, more so the irrigation demands. Through investigating the catchment’s already-existing proposed climate change policy interventions for water resources management, the study found that they were centred around boosting domestic water provisions whilst only meeting <3% of projected demands by the energy and agricultural sector. As such, by optimizing these policy plans using the WEF nexus’ Climate, Land-Use and Water Strategies (CLEWS) framework’s analytical tools, integrated climate change adaptation strategies were formulated, which were modelled to significantly improve the water storage capacity of the catchment, as well as water allocations and distribution among water users. The study concluded that the Buffalo River catchment’s surface water availability is expected to increase under climate change, however, current water storage capacity is not reliable to meet water demands throughout the 21st century. Lastly, the study also concluded that the catchment does possess immense potential for improved surface water availability to merge the gap between its water supplies and demands. Thus, the null hypotheses stipulated in this research are rejected. For discussions, policymaking and general research related to these improvements in water resources management in the Buffalo River catchment, the climate change adaptation strategies established in this research are recommended. Also, based on model evaluation statistics, the WEF nexus was successful in examining the interrelations among WEF resources, and is recommended for future studies to examine long-term integrated demand-supply strategies for WEF sectors.
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    Effects of different packaging materials and storage conditions on the quality attributes of tomato fruits.
    (2021) Dladla, Sandile Sifiso.; Workneh, Tilahun Seyoum.
    Abstract available in PDF.
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    The effects of different storage environments on the quality of stored amadumbe (Colocasia esculenta L. Schott) corms, flours, and their starches.
    (2022) Mukansi, Demian Vusimusi.; Workneh, Tilahun Seyoum.
    Abstract available in PDF.
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    Design and development of a solar powered irrigation system model for South Africa.
    (2021) Piliso, Piwe Vuyo.; Senzanje, Aidan.; Dhavu, Khumbulani.
    Abstract available in PDF.
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    The development of a sheller for bambara groundnuts.
    (2020) Nkambule, Siboniso Nhlanhla.; Workneh, Tilahun Seyoum.; Lagerwall, Gareth.; Kassim, Alaika.
    Abstract available in PDF.
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    Drying of sweet potato tubers using a naturally-ventilated solar-venturi dryer and a hot-air dryer.
    (2020) Gasa, Siyabonga Robern.; Workneh, Tilahun Seyoum.; Laing, Mark Delmege.; Kassim, Alaika.; Sibanda, Sipho.
    Abstract available in PDF.
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    Characterisation of the electrochemical properties of maize grain contaminated with aflatoxin.
    (2017) Muga, Francis Collins.; Workneh, Tilahun Seyoum.; Marenya, Moses Okoth.
    Abstract available in pdf.
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    The role of decision making and management of construction projects in fostering sustainability for intensive urban development through public housing initiatives in South Africa.
    (2018) Qwabe, Nombuso Nomfundo.; Tramontin, Vittorio.
    The current discourse in sustainable development is centred on the 17 Sustainable Development Goals stipulated in the 2030 Agenda for Sustainable Development as well as the New Urban agenda. The resilience, inclusiveness and safeness of human settlements and the need to readdress the manner in which these are planned, financed, developed, governed and managed is at the forefront of the narrative. In the South African context this soughtafter target of integrated and sustainable human settlements delivery has seen a trajectory riddled with a myriad of policies and programmes. One of the predicaments at the heart of the new urban agenda globally, and South Africa specifically, is whether population growth should be accommodated by extensive or intensive urban development. Both approaches have gained support in the South African context in recent years. The research looked at the role of decision making and management of construction projects within the context of producing sustainable housing through intensive redevelopment in South Africa and particularly in Durban. The intensive redevelopment approach indeed seems to address the ideals of the New Urban Agenda, however a case study analysis and an overview of recent research related to intensive redevelopment through building conversion and renovation has revealed that efforts to date do not address sustainability issues comprehensively. The study paid special attention to the social aspect of sustainability, which reflects recent increasing awareness that the construction industry must support the sustainable development agenda by including social considerations throughout the construction project life cycle in hopes of achieving sustainable buildings and communities. An environmentally friendly building requires only the minimizing of its environmental impact, however a sustainable building asks for more. The sense of a community is fundamental for a sustainable building, since it should increase social equity, cultural and heritage issues, human health and social infrastructure, as well as safe and healthy environments. The research adopted a multi-dimensional approach involving an extensive literature review, individual and focus group interviews with stakeholders, a questionnaire-based survey conducted with the occupants of buildings involved in intensive urban redevelopment and case studies’ analysis. Findings demonstrated that the New Urban Agenda needs to recognise and respond to drivers such as the demand for central city living from low and middle income groups desperate for the access to amenities and economic opportunities it provides. Core urban areas, inner suburbs and old transport routes are full of derelict and under-utilised land, former buffer strips and run-down buildings in need of renewal and regeneration. There are unrivalled opportunities within South African municipalities to rehabilitate worn-out infrastructure, to install new energy and communication systems, and to refurbish and construct better buildings. Rerouting capital flows to retrofit existing urban assets makes sense from a resource efficiency perspective. Long-term considerations, global thinking and local action, responsibility and transparency from a management and decision making perspective, and the purposive application of the principles of sustainability throughout a project lifecycle and to all stakeholders promotes continual improvement and distinctive steps towards archiving sustainable buildings and communities through the process of conversions and rehabilitation of existing buildings in urban areas.
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    Breeding dry bean for resistance to bacterial brown spot disease conditions in South Africa.
    (2018) Salegua, Venancio Alexandre.; Melis, Robertus Johannes Maria.
    Bacterial brown spot (BBS) disease is a major disease in dry beans in South Africa causing yield losses of up to 55%. The overall goal of the research was to improve dry bean production through identifying high yielding and stable cultivars, with resistance to the BBS disease, classifying or detecting mega environments for dry bean production and to conduct prebreeding trials that will provide information that will contribute to BBS disease breeding in South Africa. Four hundred and twenty three Andean Diversity Panel (ADP) dry bean genotypes were screened for grain yield and BBS disease resistance in three regions. The plants were inoculated with three isolates of BBS strains or inoculum at 21, 28 and 36 days after planting. Disease severity was rated at 7, 14 and 21 days after the first infection and the relative area under disease progress curve (RAUDPC) was calculated. The analysis of variance revealed significant differences (P<0.001) in grain yield and BBS severity for genotype, environment and genotype by environment interaction (GEI). Genotypes were classified as resistant, moderate resistant and susceptible based on BBS severity and RAUPDC. The study identified 21.0% of the genotypes as resistant and 41.6% as moderately resistant to BBS disease. The RAUDPC was significantly (P<0.001) negatively associated with grain yield (r= -0.55). The small seeded genotypes showed lower RAUDPC than the medium and the large seeded, and genotypes with an indeterminate growth habit showed lower RAUDPC than those with a determinate growth habit. Genotypes ADP-0592, ADP-0790, ADP-0120 and ADP-0008 were selected for both resistance to BBS disease resistance and high seed yield across three environments. The best genotypes had grain yield above 1.45 t ha-1 across sites, and above1.85 t ha-1 at individual sites, and had grain yield above the grand mean (0.87 t ha-1) and the best performing cultivar (1.13 t ha-1), and mean BBS severity below the grand mean (39.85) and the best performing cultivar (31.67). These genotypes can be useful sources of genetic resistance for future dry bean improvement.
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    The foliar micromorphology and medIicinal phytochemicalpProperties of Heteropyxis Natalensis (Myrtaceae).
    (2018) Chetty, Saiyuri Dayinee.; Naidoo, Yougasphree.
    The use of medicinal plants as a form of therapeutic healing is an ancient tradition in various regions of the world. As a result, there is a dire need to screen medicinal plants for their unrevealed pharmacological potential. The foliar micromorphology of plants enables researchers to investigate the synthesis and location of medicinal phytocompounds. Heteropyxis natalensis is a South African medicinal plant and is traditionally used in Venda and Zulu communities to treat several illnesses. This study aimed to characterise the foliar structures of H. natalensis leaves, locate the site of secondary metabolites, determine the phytochemical composition of the leaves, and investigate the antibacterial efficacies and silver nanoparticles (AgNPs) of the methanolic extract. Emergent, young and mature leaves were examined using various microscopy techniques which confirmed the presence of non-glandular trichomes as the main external appendages of the leaves. Micrographs also revealed internal secretory cavities and crystal idioblasts. Secretory cavities were observed accumulating amorphous secretions and histochemical tests detected alkaloids, phenolics, essential oils and lipids. Qualitative phytochemical analyses were conducted on hexane, chloroform and methanol leaf extracts, and detected phenolics, alkaloids, saponins, sterols and terpenes. Crude methanolic extract was further examined using gas chromatographymass spectrometry and identified several important bioactive compounds of pharmacological value. A “green approach” was used to synthesise AgNPs using the methanolic leaf extract. Characterisation studies identified spherical particles below 100 nm in size, as well as the functional groups responsible for the capping of silver ions (Ag+). The crude methanolic extract and AgNPs were screened for their antibacterial efficacy and showed inhibition of five pathogenic bacterial strains. The results obtained in this study revealed that the phytochemical compounds present in H. natalensis leaves justify the use of this species in traditional medicine.
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    Effects of water deprivation on the prevalence of gastrointestinal parasites in Nguni goats.
    (2016) Ndlela, Sithembile Zenith.; Chimonyo, Michael.
    The broad objective of the study was to determine the effects of water deprivation on prevalence of gastrointestinal parasites in Nguni goats. A cross-sectional survey was conducted on 285 farmers that kept goats from KwaNongoma in Zululand district in South Africa. Data collected included household demographics, goat production constraints, extent of water scarcity, disease challenges and prevalence of gastrointestinal parasites. Varying periods of water deprivation (0, 24 and 48 hours) on water intake, feed intake, body weight, body condition score, FAMACHA, faecal egg counts and faecal larval counts were determined. Government grant was the main source of income for households experiencing no water shortages (60 %) and those experiencing water shortages (65 %). All households kept goats for traditional ceremonies. The mean goat flock sizes were not significantly different (P > 0.05) between households that did not face water shortages (14.7 ± 1.25) and households that experienced water shortages (13.2 ± 1.23). Goats in households experiencing water shortages were 11.0 times more likely to experience water scarcity than goats from households facing no water shortages (P < 0.05). Coccidia and roundworms were the most prevalent parasites in goats from households experiencing water shortages. From the experiment, daily water intake (DWI) was the same in goats deprived of water for 0 (control) and 24 and 48 hours (P > 0.05). The daily feed intake (DFI) and the DWI: DFI ratio deprived of water for 0 and 24 hours was similar (P > 0.05). The FEC was the same in goats deprived of water for 0 and 24 hours (P > 0.05). Faecal egg counts (FEC) were highest in goats deprived of water for 48 hours (P < 0.01). Faecal larval counts (FLC) for goats deprived of water for 48 hours were almost double the counts from goats deprived for 24 hours. This implied that parasite infestation was strongly related to water intake. Correlation between water deprivation period with DFI, DWI: DFI ratio and BCS were negative (P < 0.05). The FAMACHA scores increased as the water deprivation period was increased. The FAMACHA correlated positively with FEC and FLC (P < 0.01) and negatively with BWT. There was a negative correlation between water deprivation period and BWT (P < 0.01). Pearson’s correlation coefficients between FEC with water deprivation period were positive (P < 0.01), and negative with BWT (P < 0.01) and BCS (P < 0.05). There was a positive correlation between FLC and water deprivation period (P < 0.01), whereas a negative correlation with DFI (P < 0.05). It was concluded that coccidiosis and gastrointestinal parasites were major constraints to goat productivity and were severe in households that experienced water shortages. The increased periods of water deprivation compromised goat productivity, therefore, water deprivation periods can be set to 24 hours for Nguni goats.
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    Engineering and water governance interactions in smallholder irrigation schemes for improved water management.
    (2019) Dirwai, Tinashe Lindel.; Senzanje, Aidan.; Mudhara, Maxwell.
    Smallholder Irrigation Schemes (SISs) in South Africa have reported below expectation performance, despite massive investments. A diagnosis of the SISs poor performance indicates prevalence of infrastructural deficiencies, as well as poor institutional setup. The government’s Irrigation Management Transfer (IMT) initiative compounds the problem. IMT placed irrigators in self-governance, which inadvertently made irrigators carry the burden of scheme Operation and Maintenance (O&M) costs. This study sought to investigate and evaluate how technical design principles i.e., technical aspect of irrigation design, interact with irrigation water governance for SISs in KwaZulu-Natal Province. The study hypothesized that the existing current water control infrastructure does relate to the water governance frameworks in the selected study sites. The study was carried out in Tugela Ferry Irrigation Scheme (TFIS) and Mooi-River Irrigation Scheme (MRIS). An infrastructure condition assessment was carried out followed by a root cause analysis. Questionnaires were then administered to relevant stakeholders to rate the degree of identified causal factors. Key informants ranked how water governance and infrastructure aspects are related. The data was processed using a fuzzy theory approach. Finally, structured questionnaires were administered to irrigators to establish how water governance impacted on water adequacy for crop production. A binary logit regression model was employed to process the data. Assessments revealed the poor condition of the infrastructure, such as deep cracks in canals and missing latches on hydrants. The study revealed that TFIS had a strong institutional setups according to the Closeness Coefficients(𝐶𝐶𝑖 = 0.18), and clearly defined goals and objectives for the scheme operation. However, other governance aspects such as procedures (𝐶𝐶𝑇𝐹𝐼𝑆 = 0.17, 𝐶𝐶𝑀𝑅𝐼𝑆 = 0.16) were not strong. MRIS (𝐶𝐶𝑀𝑅𝐼𝑆 = 0.20) had a good standing on rules and regulations as compared to TFIS (𝐶𝐶𝑇𝐹𝐼𝑆 = 0.14). Eight water governance related statistically significant variables that influenced water adequacy were identified. The eight variables were irrigation scheme (𝑝 = 0.000), location of plot within the scheme (𝑝 = 0.008), training in water management (𝑝 = 0.012), satisfaction with irrigation schedule (𝑝 = 0.000), irrigation training (𝑝 = 0.085), farmer knowledge of governments aims in SIS (𝑝 = 0.012), availability of water licenses (𝑝 = 0.002), and water fees (𝑝 = 0.022). A descriptive analysis showed that 24% and 86% of the farmers in MRIS and TFIS respectively, had adequate water. The study concluded that the SISs lacked an O&M plan and the farmers were not willing to opt for collective action and iii cooperate in Water Users Association (WUAs) and Irrigation Management Committees (IMCs). Some of the water governance aspects were discordant with infrastructure characteristics and requirements, consequently, impacting on the water adequacy for the irrigators. Overall, the study proved the hypothesis that the water control infrastructure does not relate with the water governance framework. This study recommends that the stakeholders involved in SISs, i.e., government, extension workers, NGOs, should aid the irrigators in policy articulation. In addition, the WUA and IMCs should provide incentives to motivate farmers to actively participate in scheme O&M.
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    Haematological, blood glucose and insulin profile in sprague-dawley rats experimentally infected with trichinella Zimbabwensis and plasmodium berghei anka.
    (2017) Nkemzi, Achasih Quinta.; Mukaratirwa, Samson.; Murambiwa, Pretty.
    Malaria and helminth co-infection have been widely reported by other researchers. Despite the increasing knowledge on co-infection, the impact of helminths and malaria on humans and laboratory animal models remains uncertain. Furthermore, studies have associated co-infection to the induction of hypoglycemia. Accordingly, the effect of Plasmodium berghei ANKA and Trichinella zimbabwensis co-infection on haematology, blood glucose and insulin profiles was investigated in male Sprague-Dawley rats. The study was investigated using 168 Sprague-Dawley rats that were assigned into four groups of 42 rats each; control (C), P. berghei (Pb), T. zimbabwensis (Tz) and P. berghei (Pb) + T. zimbabwensis (Tz) co-infection groups. The Tz group was orally infected with 3 muscle larvae/g animal body weight of Tz strain (Code ISS1209) at day 0. The Pb group received (1×105 PRBCs) of P. berghei ANKA using intraperitoneal injection and Pb + Tz co-infection group received 3 muscle larvae/g animal body weight at day 0 followed by intraperitoneal injection of 1×105 PRBCs at day 28 post-infection with Tz while the Control group was uninfected. Plasmodium berghei parasitaemia (%), Tz adult worms (AWs) and muscle larvae (ML), blood glucose, liver and muscle glycogen, insulin concentration as well as the cumulative body weight were determined. Results showed a significant increase in parasitaemia for Pb + Tz co-infection at day 3 and 4 PI compared to Pb group. Adult Tz worms and ML recovered showed no significant difference (P > 0.05) between the co-infection and the Pb group (P > 0.05). Blood glucose levels for co-infected group were also not significantly different compared to the control although the Pb group showed a decrease in blood glucose at day 7 and 14 PI. The co-infection group showed a higher mean glycogen accumulation compared to Tz group although there was no significant difference between the two groups. Tz group and Pb + Tz co-infection groups showed a decrease in liver glycogen at day 7 Pl and at day 14 PI. The Pb + Tz co-infection group showed a significant decrease in glycogen compared to the control. After Pb infection, there was a decline in insulin for both Tz and Pb + Tz co-infection whereas at day 7 only the Pb + Tz co-infection group presented a decrease in insulin compared to the control. Therefore, the current study revealed that co-infection increased Pb parasitaemia and glycogen levels without decreasing the host blood glucose concentration. Early increase in Pb parasitaemia demonstrated that co-infection could alleviate parasitaemia severity in the host.
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    Development of a naturally-ventilated solar energy-assisted maize seed store.
    (2018) Mdlalose, Siphiwe Nduduzo.; Workneh, Tilahun Seyoum.; Laing, Mark Delmege.; Sibanda, Sipho.
    The seed industry continues to face losses during seed storage, especially in Africa. Moreover, there is high loss of seed viability during storage, mainly due to the poor ventilation in seed storage structures, which results in the development of storage fungi. In this study, the main objectives were to construct, to evaluate the solar energy assisted maize seed store. A 22-m3 room was converted to a seed storage room by retrofitting a chimney on its wall and a solar collector on its roof. Different chimney sizes were investigated in order to identify which size would be best for the construction of a naturally-ventilated seed storage room. The chimney sizes that were used included those with a diameter and a height of 200 mm x 3600 mm, 200 mm x 4800 mm, 300 mm x 3600 m and 300 mm x 4800 mm. The parameters, air velocity in the chimney duct, as well as the air temperature and relative humidity at the inlet, centre and outlet of the storage room, were recorded during the seed storage period. A naturally- ventilated seed storage room was developed based on the results obtained. A naturally-ventilated seed storage room was then evaluated in terms of its effectiveness to preserve the quality of the stored maize seeds. To compare the performance of the modified storage room, a room with similar storage capacity, but without the retrofitted components, was used as a control. Maize seeds were stored in each storage room for the duration of three months. Samples were taken every two weeks for germination, moisture content and seed vigour analyses. Both the diameter and height of the chimney were found to have a significant (P≤0.05) influence on the air ventilation rate inside the storage room. A seed storage was therefore developed using a 300 mm x 4.8 m chimney size, which performed better than the other chimney sizes that were explored in this study. The relative humidity in the control storage room was significantly (P≤0.05) higher (60.6 ± 5.87%) than the relative humidity in the modified storage room (40.1 ± 3.21%). The moisture content obtained in the control room was significantly (P≤0.05) higher (13.3%) than the moisture content obtained in the modified storage room (12.6%). The initial germination was 99%. The seed germination percentage obtained after three months of storage in the modified storage room was significantly higher (P≤0.05) (98.5 ± 0.85%) than the germinations percentage obtained in the control storage (96.8 ± 1.49%). The seed vigour obtained in the modified storage was significantly higher (P≤0.05) than the seed vigour obtained in the control room. Thus, a naturally-ventilated seed storage room was tested and was found to preserve the quality of the seeds over the duration of storage.
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    Evaluation of the effects of pre-drying treatments and drying methods on the drying kinetics and quality of Tommy Atkin mango slices.
    (2017) Mugodo, Khuthadzo.; Workneh, Tilahun Seyoum.; Sibanda, Sipho.
    Mango is a perishable fruit, harvested once a year during the summer season. Smallholder farmers growing mango experience relatively high post-harvest losses because they receive large volumes of produce at the same time. Drying is a preservation method proven second to cooling in performance. In South Africa, dried mango fetches higher returns compared to canned mango, and mango juice, atchar and jam. Open-Air solar Drying (OAD) is a popular drying method used for producing dried mango. However, this method of drying has setbacks resulting in produce quality loss. Convective Oven Drying (OVD) is a more efficient drying method, however, it has high-energy consumption. In South Africa, there is lack of research on hot-air drying methods, as well as their performance when drying mango fruit. With the current shift in use of renewable energy for drying operations, research is focusing on improving solar drying technologies. These include increasing the drying capacity and reducing the drying time through modifying a greenhouse. Considering the research gap in South Africa on drying technologies and the limitations of open-air solar drying, this study comparatively assessed the performance of three drying methods, namely, (a) Convective Oven Drying (OVD), (b) Open-Air solar drying (OAD) and (c) a Modified Ventilation Solar Drying (MVD). OVD was carried out at a set temperature of 70˚C, OAD and MVD at ambient temperature of 15.55˚C -36.77˚C, at an RH of 22.96%-79% and solar radiation of 317W.m-2- 1016 W.m-2. The MVD improved the ambient conditions to obtain an average maximum temperature of 64.26 ˚C and RH of 17.6%. The drying time was longer for mango slices dried in OAD, MVD and OVD, respectively. The lemon juice pre-treatment did not affect the drying time. The drying time was reduced for 3 mm, as compared to the 6 mm and 9 mm dried mango slices, due to the relatively high drying rates. Drying took place in the falling drying rate period for most mango samples, indicating that diffusion was the driving mechanism in the drying experiments. The effect of the drying methods on the drying kinetics of mango slices (3 mm, 6 mm and 9 mm) as well as the effect of lemon juice pre-treatment was investigated. Non-linear regression analysis was used to assess the empirical model that best fits the experimental moisture ratio data. The quality parameters that were evaluated included the colour, rehydration, sensory properties, changes in mango microstructure and microbial changes. The empirical model that was best fit for the drying data was that of the Midilli et al., followed by Page model because a higher R2, a lower root mean square (RMSE) and a lower chi-square (X2) was obtained from non-linear regression analysis. A quality analysis indicated that colour change (ΔE) was not significantly (P>0.05) affected by pre-treatment, although control samples that were dried in the OAD had a relatively higher colour change, resulting to browning. The rehydration ratio and electronic microscopy (SEM) showed structural changes in dried samples, with thicker mango slices having a relatively lower rehydration ratio, and the SEM scans dominated by cracks and pores, which were much more visible for 9 mm mango slices. Sensory evaluation results indicated that the panellists preferred the flavour and colour of pre-treated 3 mm mango slices compared to thicker control and pre-treated dried mango slices. In addition, the overall acceptability of dried mango was relatively higher for MVD-dried, than OVD- and OAD-dried mango slices, respectively. The fungi and anaerobic bacteria levels found in dried mango slices were higher than the recommended levels of 1x103; however, there were no pathogenic microbes detected in the fresh and dried samples. The study findings show that dried mango is an acceptable produce to consumers, especially in areas like Kwazulu-Natal, were mango is scarce. MVD is a drying method, which is practical and can solve the shortcomings of OAD. This method is a renewable energy alternative to OVD and further improvement is required to increase temperature and ventilation is necessary to reduce drying time.
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    Improving rainfall erosivity estimates for the design of soil conservation structures in South Africa.
    (2018) Johnson, Robyn Anne.; Smithers, Jeffrey Colin.; Senzanje, Aidan.
    Soil erosion is a major problem, both in South Africa and globally. Soil erosion reduces the productivity of land and has major environmental, as well as economic, impacts. South Africa, in particular, experiences considerable challenges in combatting soil erosion owing to a combination of factors. Examples of these factors include low vegetal cover as a result of arid climatic conditions, as well as intense thunderstorm activity. As more data and computing power become available, it is important that approaches to the design of soil conservation structures and design tools be updated, in order to reduce soil erosion. In this study, literature has been reviewed in order to obtain an overview of mechanical soil conservation measures in South Africa, soil loss estimation models currently used and design approaches to the determination of contour bank intervals. Literature showed that site-specific evaluation, using soil loss prediction tools, is the preferable approach to determining contour bank intervals, rather than the use of empirical equations. It was also found that the Revised Universal Soil Loss Equation (RUSLE) held the most potential as a model, in terms of creating a design tool for the design of soil conservation systems in South Africa. This was due to manageable input requirements as well as reliability – a result of widespread and extensive application of the model. This study applied the erosivity density approach in order to calculate rainfall erosivity (i.e. the ability of rainfall to cause erosion) across South Africa. Owing to the paucity of suitable short duration rainfall data, a second approach was attempted in which rainfall erosivity calculated from short duration data was related to daily rainfall data characteristics. It was found that the both approaches resulted in erosivity density patterns similar to what had been determined in previous studies. The erosivity density method produced results with a very fine level of detail, while the daily data method resulted in a more general overview of erosivity patterns and did not pick up localised variations as effectively. The erosivity density method showed lower rainfall erosivity values than the daily data method, in general. It also produced a much lower maximum annual rainfall erosivity than the daily data method (5 866 vs. 16 399 The verification of the interpolation of the erosivity density values gave poor results (an overall error of 75 %), indicating that the spatial density of the data was too low. This was improved in the daily data approach through the use of a greater number of daily rainfall stations, v achieving an overall interpolation error of 43%. However, when verifying the results against observed erosivity at test stations, the erosivity density method performed better, achieving an error of 55 %, compared with 91 % for the daily data method. Both methods showed potential, but require a larger network of short duration stations, in order to improve accuracy. A tool was developed to assist in contour interval determination. This took the form of a Microsoft Excel spreadsheet. The tool utilised the updated rainfall erosivity values determined in the study and focussed on determining recommended contour intervals in sugarcane plantations. The tool took into account the timing of erosive rainfall relative to crop development and tillage operations. Various scenarios were modelled and the results of the spreadsheet were compared to current methods used in the sugarcane industry. The spreadsheet was found to be highly sensitive to slope and the results suggested that soil erosion in sugarcane plantations has previously been underestimated, particularly on steep slopes. The study highlighted the need for ongoing research in the field of soil conservation.