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Effects of seaweed-based bio-stimulant kelpak© on chilling injury incidence in tomato (solanum lycopersicum L) fruit during postharvest cold storage
Full text linkThesis (M. Agriculture Management (Plant Production)) -- University of Limpopo, 2025Refer to documen
Evaluation of periphyton utilization by oreochromis mossambicus and clarias gariepinus in aqua dams in Limpopo Province, South Africa
Full text linkThesis (Ph. D. (Aquaculture)) -- University of Limpopo, 2025The high cost of fish feed in developing countries makes it imperative to develop aquaculture technologies that can produce natural food in production systems without increasing input costs. Periphyton-based aquaculture promotes the growth of periphyton on submerged substrates in water, which serves as a preferred natural food forvherbivorous and omnivorous fish such as tilapia and African catfish. Tilapia and African catfish are one of the most widely cultured species in Africa. In this study, the utilisation of periphyton by Oreochromis mossambicus (Mozambique tilapia) and Clarias gariepinus (African catfish) in aqua dams with net, plastic and stone substrates was investigated. The study aimed to reduce the cost of fish feed in rural aquaculture by enhancing the utilisation of periphyton by Mozambique tilapia and African catfish in aqua dams. Locally available materials were used as substrates for growing periphyton in the aqua dams. Periphyton dynamics in periphyton-based aquaculture are influenced by several factors thus, it was important to first determine the composition of periphyton in aqua dams before stocking the fish. The growth of periphyton on substrates in water also enhances the growth of bioseston in the water column. Therefore, the effect of substrates on periphyton and bioseston was explored simultaneously to fully understand the periphyton dynamics in aqua dams in summer and winter. Net, plastic and stone were deployed separately in the nine aqua dams in a completely randomised design in winter and summer. The experiment ran for 21 days in each season. The periphyton and bioseston were categorised as periphytic algae, metazoans, ciliates, protists, and aquatic invertebrates to easily distinguish the periphyton and bioseston communities. Periphytic algae was the most abundant category on all substrates in both winter and summer probably because they have adaptive features that enable them to thrive in various environments. The composition of periphyton and bioseston in the aqua dam with net, plastic and stone during winter and summer showed that substrate, season and grazing played a significant role. The composition and abundance of periphyton and bioseston were significantly higher (P < 0.05, ANOSIM) on the net and lowest on the stone substrate in both winter and summer. The net substrate also had the highest periphyton biomass (in terms of dry matter) while the stone substrate had the lowest in both summer and winter. This was because the texture, surface area and position of the substrate influenced the abundance and composition of periphyton and bioseston in aqua dams. Summer had higher periphyton and bioseston abundance than winter because the temperature was optimal for their growth Network analysis was later used to determine the pattern of the community structure of periphyton and bioseston in aqua dams in winter and summer and showed a weak community structure. This was caused by low genera diversity due to the similarities in water quality parameters and the high abundance of periphytic algae in both seasons. This indicated that the genera on one substrate were most likely to be found on another substrate despite the season. Subsequent to understanding factors affecting periphyton and bioseston composition in aqua dams with substrates, fish were then stocked into the aqua dams. To determine the utilisation of periphyton and bioseston by the fish in the aqua dams, three feeding regimes were designed. In the first feeding regime, the fish were fed every day (twice a day) and this was designated: N100, P100, and S100. The first feeding regime (N100, P100 and S100) represented the control because fish are normally fed twice every day at fish farms. In the second feeding regime, the fish were fed commercial pellets every other day (twice a day), and this was designated: N50, P50, and S50. In the third feeding regime, the fish were fed every third day (still twice a day), and this was designated N33, P33, and S33. Mozambique tilapia fingerlings (5.44 ± 0.81 g, mean ± SE) were stocked into the aqua dams with net, plastic and stone substrates in a completely randomised design for six weeks. Unexpectedly, specific growth rate and condition factor were significantly (P < 0.05, MANOVA) higher in aqua dams with plastic substrates. In prior experiments in aqua dams without fish, the net substrate had the highest periphyton biomass. However, the net substrate did not result in the highest fish growth rate (Chapter 4).This was probably because periphyton and bioseston in aqua dams with plastic substrate were accessible and of high quality. This shows that the periphytic algae, metazoans, ciliates, protists, and aquatic invertebrates provided sufficient protein, energy, and lipids to compensate for the nutritional value of the deprived commercial pellets. Furthermore, it was concluded that commercial pellets can be reduced by 50 to 67 % in aqua dams with periphyton substrates. Mozambique tilapia of three different size groups (2.62 ± 0.01 g, 5.08 ± 0.02 g and 25.24 ± 0.29 g; mean ± SE) were further observed for 24 hours to determine their feeding preferences between periphyton and bioseston in fibreglass tanks. The results showed that Mozambique tilapia did not show a preference between periphyton and bioseston, the fish was not actively selecting any food items. This was because Mozambique tilapia can nip and scrap periphyton from substrates and also filter feed on bioseston using gill rakers. Furthermore, the most abundant and dominant periphyton and bioseston in the fibreglass tanks were also abundant in the stomachs of all tilapia size groups. This indicates that Mozambique tilapia was ingesting the most abundant periphyton and bioseston. Diatoms were also abundant and dominant in the stomachs of all tilapia size groups but also abundant in the faecal matter. This indicates that diatoms were not digested, probably because tilapia lacked silica-reinforced teeth to break the diatom’s cell wall. The utilisation of periphyton and bioseston by African catfish was also explored. The same experiments and feeding regimes mentioned above were adopted to determine if African catfish is a good candidate for periphyton-based aquaculture. African catfish (200.2 ± 22.74 g, mean ± SD) were also stocked in the aqua dams in a complete randomised design for six weeks. The results showed that in aqua dams with net and plastic substrates, the highest specific growth rate was recorded in N100 and P100. However, in aqua dams with stone substrates, the highest specific growth rate was recorded in S33. Both N100 and P100 represented the control where the African catfish were fed commercial pellets twice, every day. The fish in S33 aqua dams were fed commercial pellets every third day. This indicates that catfish in S33 were able to utilise periphyton on stone substrates since the growth rate was comparable with the controls. This was attributed to its large lower jaw extensibility which enabled it to scoop periphyton from the stone substrates. This suggests that stone substrates can used in aqua dams stocked with African catfish to reduce commercial pellet input by 67 %. In the prior experiments, the stone substrate had the least periphyton composition and biomass, but this suggests that its nutritional value was sufficient to compensate for the nutritional value of the deprived commercial pellets. The results also showed that each substrate significantly influenced the growth performance of African catfish differently. However, there was no distinct pattern to conclude where the fish grew faster between the net, plastic and stone substrates. This was probably because the net substrate had the highest periphyton abundance and plastic had more genera of animal origin while the periphyton on the stone was more accessible to African catfish to easily scoop. The results also showed that African catfish selectively fed on insects, Chironomidae larvae, and Cladocera. Furthermore, insects and Chironomidae were important food items in the diet of African catfish across the different substrates. This was because African catfish have predatory behaviour and commonly prefer food items of animal origin. However, diatoms, Microcystis sp. and Difflugia sp. dominated the faecal matter indicating that African catfish lack gastric juices and silica-reinforced teeth to digest them. Lastly, an aquaculture recirculating system was designed to determine the impact of periphyton-based biofilters on water quality parameters. To determine the efficacy of a periphyton-based biofilter in maintaining optimal water quality parameters for tilapia culture, Mozambique tilapia (5.00 ± 1.14 g, mean ± SD) was stocked in the tanks. Net, plastic and stone were used as biofilters in duplicate in a completely randomised design. Nitrifying bacteria were not seeded but the periphyton was allowed to form naturally for three weeks before commencement of the experiment. The water quality parameters were monitored daily for three weeks to determine the overall performance of the periphyton-based biofilters. The water quality parameters were also determined for a period of 24 hrs at four-hour intervals (once every week) to monitor the diurnal dynamics in the periphyton-biofilters. The results showed the diurnal mean levels mirrored the average water quality parameters across the periphyton-biofilters over the period of three weeks. Nitrate levels significantly varied (P < 0.05) between the periphyton biofilters, net periphyton-biofilter registered the highest nitrate levels and stone registered the lowest levels. This indicates that nitrification effectively occurred in the net periphyton-biofilter contributing to the accumulation of nitrate. However, the accumulated nitrate was within the optimum range for farming tilapia. Nitrite was significantly higher (P < 0.05) in the plastic periphyton-biofilter than in net and stone periphyton-biofilter. High nitrite levels probably indicate there was imbalanced nitrite-oxidising microbial activity which led to nitrite accumulation in the plastic periphyton-biofilter. Nitrite can be toxic to tilapia when it's above 1.0 mg/l. However, the recorded level of nitrite was within the optimum range for farming tilapia, below 0.5 mg/l. The stone periphyton-biofilter registered the highest (P < 0.05) ammonia levels and plastic registered the lowest levels. The accumulation of ammonia indicates that nitrification was not effective and inadequate in the stone periphyton-biofilter. Even though ammonia was highest in the stone periphyton-biofilter, it was still within the farming range for tilapia. The total phosphate recorded in the periphyton-biofilter was slightly higher than that recorded in the aqua dams. This suggests that the periphyton community on the plastic substrate was not dominated by algae that can take up phosphate in the form of inorganic phosphorus. Dissolved oxygen and pH levels were optimum for tilapia and water purification processes in all the biofilters. The net was an effective periphyton-based biofilter since it was able to maintain the toxic ammonia and nitrite at minimal levels. This study recommends using periphyton substrate in aquaculture to reduce feed costs. Durable plastic substrates can be used in aqua dams stocked with tilapia to reduce commercial pellet input by 50 to 67 %. Stone substrates can used in aqua dams stocked with African catfish to reduce commercial pellet input by 67 %. Nonetheless, the use of other substrates needs to be explored. Furthermore, the study recommends using periphyton-based biofilters to maintain the water quality parameters optimum for fish production in a recirculating system. In this study, the net was the most efficient periphyton-based biofilter and we recommend that the net periphyton-biofilter be tested in a large-scale production system. Further experiments should be conducted to determine the feeding preference of African catfish between periphyton and bioseston.National Research Foundation (NRF) and
Aquaculture Research Unit (ARU
Tillering propensity and crop water use of different sorghum varieties under varying irrigation regimes
Full text linkThesis (M. Agricultural Management (Plant Production)) -- University of Limpopo, 2025Tillering is one of sorghum’s adaptive traits to water availability, which can ‘make or
break’ crop yields depending on cultivar genetics. The complex interaction between
water availability and genetic expression makes tiller contribution to yield difficult to be
predicted and quantified. Additionally, contributions of sorghum tillers and main stem
to ‘yield per drop’ and water use under different water availability and sorghum
cultivars have not been quantified. Therefore, this study aimed to evaluate tillering
propensity and water use of sorghum cultivars under complex tiller regulating
practices, hence showcasing tiller contribution to sorghum yields and their water
productivity under different sorghum cultivars and varying irrigation regimes. A
literature review on practices and factors that regulate tillering was done to provide
guidelines on the key practices and factors that regulate tillering in sorghum to
enhance the productivity of tillers and yield. Highlighting the effective management
practices that can improve grain yield by prioritising resource allocation hence
minimizing competition among tillers. Moreover, the study emphasized that the
dynamics of tillering must be understood under varying management practises to
maximize the tiller contribution to yield and ‘yield per drop’. As such, the field trial was
conducted to quantify the tiller contributions to yield, water use, and water productivity
at the University of Limpopo experimental farm. The study was carried out as a 3 x 4
factorial, laid out as a split-plot and arranged in a randomized complete block design
(RCBD). The plots comprised of two irrigation regimes assigned as the main (full,
deficit) which were compared to rainfed (unirrigated control), and four sorghum
cultivars as subplots (Mr Buster, PAN606, Macia, and a local landrace) replicated
three times. For addressing the tiller contributions to yield, water use and water
productivity, phenological development, maximum canopy cover, plant height, stem
width, biomass accumulation, number of tillers and fertile tiller percentage, harvest
index, grain yield, soil water content, evapotranspiration, water productivity and the
tiller contributions were collected during the growing season. The interactive effects of
cultivar selection and irrigation regimes significantly influenced shoot dry biomass,
grain yield, water use, and water productivity. Significantly higher shoot dry biomass
(5.70 ton/ha), grain yield (7.10 ton/ha), and water productivity (2.58 kg/m3
) were
recorded from the local landrace when it was cultivated under deficit irrigation. On the
contrary, the lowest sorghum yield (3.04 ton/ha), shoot dry biomass (1.78 ton/ha), and
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water productivity (1.19 kg/m3
) was obtained by Mr Buster with high water use (239.9
mm). However, it had statistically comparable water use and water productivity with
PAN606 (225.5 mm and 1.34 kg/m3
) and Macia (226.2 mm and 1.24 kg/m3
),
respectively. The great performance of landrace was attributed to longer maturity,
number of tillers produced and the adaptability to local environment. The landrace had
high percentage of fertile tillers (81%) compared to Mr Buster (51%). This suggest that
landrace is good at using low water to produce reasonable yield and can be planted
to maximize yield with less water used. Tillers made a substantial contribution to both
overall grain yield and water productivity, accounting for 57% of the total yield
compared 43% contribution of the main stem. Similarly, tillers contributed 53% to water
productivity, while the main stem contributed 47%. Despite this, the main stem
remained the statistically dominant yield contributor across different irrigation regimes
and cultivars. The early-emerging tillers T1 (27 %), T2 (15 %), and T3 (9 %) proved to
be the most productive due to better access to plant available assimilates. In contrast,
the later-emerging tillers T4 (4 %) and T5 (2 %) were less competitive and had a
minimal impact on yield, as they had low access to the resources needed by the plant.
The reported tiller contributions to yield ranges from 5 – 78 %, hence, the conclusion
was drawn that tillers contributing less than 5% to yield are considered non-significant.
Additionally, tiller 1 to tiller 3 consistently contributed within a range of 5 – 78% across
all irrigation regimes and cultivars. Therefore, it is suggested that farmers prioritize
harvesting tillers up to tiller 3, as tillers beyond this point (tiller 4 and tiller 5) do not
contribute significantly to overall yield. It is then recommended that cultivating landrace
under deficit irrigation and focusing on tillers up to tiller 3, could achieve sustainable
yields and maximize the contributions of productive tillers. However, the study was
limited to a single site and season planting. Therefore, it is recommended that future
research include multi-location trials and multiple growing seasons to capture the
spatial and temporal variability of environmental conditions. Furthermore, additional
research should explore specific agronomic practices designed to selectively boost
the productivity of tillers while reducing the presence of unproductive onesFoodBev SET
Teachers' perspectives on formative assessment in physical sciences education
Full text linkJournal article published in African Perspectives of Research in Teaching and Learning Journal Issue 1, Volume 9, 2025This study examined teachers' perspectives on the influence of formative assessment on Physical Sciences learners' academic achievement, attitudes, and self-regulation skills. Drawing from qualitative data, the research aimed to understand how formative assessment practices, such as feedback, peer assessments, and self-assessment strategies, shaped learners' engagement and academic outcomes. A purposive sample
of 20 Physical Sciences teachers was selected to provide insights into the role formative assessment played in fostering not only academic success but also positive attitudes towards science and enhanced self regulation skills. Through teacher semi-interviews, the study explored how these assessment strategies supported learners' ability to monitor their own progress, adapt their learning approaches, and maintain
motivation in a challenging subject area. A thematic analysis was used to analyse the interview data. The findings suggested that formative assessment was a key pedagogical tool that contributed to improved learner performance, more positive attitudes towards Physical Sciences, and the development of essential
self-regulation skills. This research had significant implications for the integration of formative assessment into science teaching and learning practices, highlighting its potential to support holistic learner development
Negotiating professional and personal selves : the experiences of black academic women in South African Higher Education Institutions : a conceptual reflection
Full text linkJournal article published in African Perspectives of Research in Teaching and Learning Journal Issue 3, Volume 9, 2025 Special IssueThis article explores the intricate landscape of higher education more specifically, South African higher education. It mainly focuses on the experiences of Black female academics since the end of apartheid in 1994. Despite the number of women, entering academia having increased, significant challenges remain, such as barriers to career advancement and the influence of intersecting identities like gender, race, and motherhood. The under-representation of women in leadership roles underscore systemic issues, rooted in stereotypes and unconscious biases that undermine women's competence, character and, authority. The paper employs Nancy Fraser's three-dimensional theory of justice and Crenshaw's intersectionality framework to investigate these dynamics, emphasising the need for economic redistribution, cultural recognition, and political representation. It discusses how, institutional policies often marginalise women's voices in decision-making processes, contributing to a crisis of gender inequality within academic echelons. The findings indicate that while initiatives have been employed to promote gender equality, the unique challenges faced by Black women in academia remain largely unattended. This study aims to magnify the voices of these women, encouraging a deeper understanding of their experiences and the structural barriers they encounter in their professional journeys
Exploring pre-service Physical Sciences teachers’ conceptions and misconceptions of the nature of science
Full text linkJournal article published in African Perspectives of Research in Teaching and Learning Journal Issue 4, Volume 9, 2025This study investigates pre-service physical sciences teachers' conceptions of the Nature of Science (NOS) within the context of South Africa's educational goal of fostering scientific literacy. Guided by a 21st-century skills framework, the study explores how these future educators perceive and understand NOS—a foundational component for effective science instruction. This study adopted a phenomenographic design. Data were gathered through semi-structured interviews with ten fourth-year physical science and mathematics education majors at a South African university and analysed using thematic analysis. Findings reveal a distinct perspective among participants, who largely view NOS as absolute and objective, contrasting with the nuanced and evolving nature highlighted in existing literature. This study underscores the importance of addressing and rectifying potential misconceptions regarding scientific knowledge among pre-service teachers to better equip them for their roles as science educators, ultimately supporting accurate scientific literacy in their future classrooms
Crisis communication for management of government disaster : the case of Life Esidimeni in Gauteng Province, South Africa
Full text linkThesis (M. A. (Communication Studies)) -- University of Limpopo, 2025In 2015, the Gauteng Department of Health announced the termination of its contract
with Life Esidimeni, a private healthcare provider which had been outsourced by the
department to provide specialised psychiatric care to state patients. Within months of
this announcement, more than 1500 patients had been transferred to the care of over
100 facilities including non-profit organisations (NPOs) and state-owned psychiatric
hospitals. These facilities had inadequate resources including infrastructure and care
workers, ultimately resulting in the deaths of 144 psychiatric patients. The purpose of
this study was to investigate how government officials managed the Life Esidimeni
crisis from the perspective of crisis communication. Using qualitative textual and
thematic analysis, this study adopted Coombs’ Situational Crisis Communication
Theory (SCCT) and Seegers’ Best Practice Model as frameworks to examine how the
government communicated during the Life Esidimeni crisis. The study adopted a
qualitative research approach and document analysis method for data collection. The
study revealed that during the Life Esidimeni crisis, communication and stakeholders’
active participation were inadequate. Furthermore, the use of combined crisis
communication strategies by government health officials demonstrated a
misunderstanding of the nature of the crisis. The study recommends that organisations
should refine their crisis communication plans based on the recommendations by the
Situational Crisis Communication Theory and Best Practice Model to promote
stakeholder engagement and develop unique crisis communication strategies for
crises in different cluster
Knowledge of pregnant women diagnosed with hypertensive disorders regarding treatment and self-care at a selected hospital, Limpopo Province, South Africa
Full text linkThesis (M. (Nursing)) -- University of Limpopo, 2025The study aimed to determine the knowledge of pregnant women diagnosed with hypertensive disorders regarding treatment and self-care at a selected hospital in Limpopo, South Africa. A quantitative research approach and a descriptive research design were employed. Simple random sampling was used to select 119 pregnant women diagnosed with hypertensive disorders, and data were collected using a questionnaire. The analysis was performed using the Social Sciences Statistical Package (SPSS version 27). The findings revealed that 45% of the women diagnosed with hypertensive disorders were aged between 30 and 39 years, and most respondents (87%) understood the treatment instructions provided by their doctor or nurse. This understanding is attributed to the fact that a significant portion of the pregnant women (48%) had received tertiary education. Additionally, the results indicated that most pregnant women diagnosed with hypertensive disorders had knowledge about self-care.
The study recommends that health facilities should have teaching programs for pregnant women diagnosed with hypertensive disorders. The study also recommends that a multidisciplinary approach be used when managing pregnant women diagnosed with HDP. A similar study is also recommended to assess the knowledge of pregnant women diagnosed with HDP that will include a large population from different facilities for generalizatio
The relationship between attachment styles and contraceptive intent among female University of Limpopo Students, South Africa
Full text linkThesis (M. A. (Clinical Psychology)) -- University of Limpopo, 2024This study examined the relationship between attachment styles and contraceptive intent among female University of Limpopo students in South Africa. The primary hypotheses proposed positive associations between secure attachment and high contraceptive intent, as well as varying relationships for avoidant and anxious attachment styles. Utilising multinomial logistic regression analysis, the study found no significant overall relationship between attachment styles and contraceptive intent, with a chi-square value of 8.992 and a p-value of 0.774. Notably, avoidant attachment was associated with low contraceptive intent, while anxious attachment was associated with high intent. Secure attachment showed no significant effect. The Pseudo R-squared values indicated weak predictive power, with Cox and Snell at 0.023, Nagelkerke at 0.116, and McFadden at 0.106. These results suggest that attachment styles may not be reliable predictors of contraceptive behaviour, highlighting the need for further research into additional factors influencing contraceptive intent. The study underscores the complexity of reproductive decision-making and emphasises the importance of exploring diverse populations and contextual influences in future research
The effects of electricity prices and electricity supply on the economic growth of South Africa for the period 1993 to 2022
Full text linkThesis (M. Com. (Economics)) -- University of Limpopo, 2025As an energy source, electricity is fundamental in driving economic growth, particularly in emerging economies like South Africa. This study investigated the effects of electricity prices and supply on South Africa's economic growth over the 1993 to 2022 period. This is performed by adopting and extending the energy-growth model, this study contributes to the existing literature on energy economics. To achieve the research objective, unit root tests were conducted to identify the integration order of variables, followed by the Autoregressive Distributed Lag (ARDL) approach to estimate short- and long-run relationships. The bounds test confirmed a long-run equilibrium relationship between the variables in the energy-growth model.
The ARDL results revealed that electricity prices positively influence economic growth in the short and long run. The electricity supply negatively impacts economic growth in the short run but is statistically insignificant in the long run. Additionally, the results indicate a negative and statistically significant long-run relationship between labour force participation and economic growth, highlighting potential structural inefficiencies in South Africa's labour market. These findings empirically validate aspects of the energy consumption theory while emphasising developing country-specific dynamics. The study recommends proactive government policies to address high electricity prices and irregular supply, which pose significant risks to economic developmen