Masters Degrees (Agricultural Engineering)

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Assessing the performance of smallholder irrigation in South Africa and opportunities for deriving best management practices.
(2012) Gomo, Taziva.; Senzanje, Aidan.
South Africa is a water scarce country. With the increasing demand of water from other users, irrigation, as the largest water user, has to find ways to produce more per drop and meet the food demands of the growing population. Enhancing the performance of smallholder irrigation schemes (SHI) is one way of saving water since they are fast becoming the largest water users in South Africa and the world over. Performance in the smallholder sub-sector is reportedly below the expectations of stakeholders. However, performance in smallholder irrigation schemes is multi-dimensional and can be looked at from different perspectives. This study assessed the technical performance of the Mooi River Irrigation Scheme (MRIS) from the technical managers` and the farmers` points of view and integrated them into one to derive a comprehensive set of best management practices (BMPs) for the scheme. This was done acknowledging that the farmer is now the water manager in line with Participatory Irrigation Management (PIM) and Irrigation Management Transfer (IMT). Three performance indicators related to water supply and delivery: conveyance efficiency, dependability of irrigation intervals between water applications and relative irrigation supply, and two agricultural performance indicators namely, output per unit irrigation supply and output per unit water consumed, were assessed during the spring and summer of the 2010/11 season. The field measurement method was used for the assessment of these indicators as opposed to the faster and more encompassing remote sensing method, due to resource constraints. The Velocity-area method was used to measure flow-rates in canals and crop water demands were estimated from FAO Cropwat 8.0 and Aquacrop 3.1. The results show an overall scheme conveyance efficiency of 86.4%, a maximum dependability of irrigation intervals between water applications of 2.57 in spring and a scheme relative irrigation supply of 1.48. Agricultural performance indicators, output per unit irrigation supply and water productivity per unit crop evapotranspiration (ET), were found to be 0.64 kg/m3 and 5.37 kg/m3 on average for cabbage, respectively. Farmers` satisfaction with taking an irrigation service can be used as a measure of the scheme`s performance. A questionnaire was administered among farmers to gather their views on the performance and to determine the factors that significantly influence their satisfaction status with taking the irrigation service at MRIS. Information collected from the questionnaire include age, gender, irrigation training, timeliness of water delivery, water distribution among the blocks, farming experience, farmer involvement in inspection of irrigation infrastructure and maintenance, among others. Farmers` were also asked for suggestions on improving the performance of their scheme. Their responses were analysed using a multinomial logit model. Results showed that 57% of the farmers are satisfied with using the irrigation service at MRIS, 30% are not satisfied, while 13% are neutral. Eight factors were found to be statistically significant in influencing the farmers` satisfaction status namely: location with respect to the water diversion point, location within a block from the main canal, age of the farmer, education level attained by the farmer, farming experience, the number of plots a farmer owns, fairness of water distribution across the blocks and the number of days a farmer accesses water The technical performance indicators assessed and the suggestions from the farmers on the way to improve performance of MRIS allowed the selection of the BMPs for the scheme. A set of seven BMPs based on farmer suggestions was derived. BMPs used as a guideline. The farmers were also tasked with the ranking of the derived BMPs according to their preference. The collected data was then ranked through an Analytic Hierarchy Process (AHP). The results show that establishment of and adherence to an irrigation schedule was the most preferred BMP by the farmers, while volumetric measurement of irrigation water used by each block was the least preferred. This study concludes that the performance of MRIS is comparable to other schemes and that farmers are aware of the problems bedevilling their scheme. It is also concluded that the performance of the scheme meets the farmers`, the key stakeholders, expectations and that irrigation scheduling is the most preferred BMP. The study recommends that farmers be more involved in performance assessments and management of their schemes. It is crucial to ensure that the recommended BMPs are acceptable to the farmers in the scheme. The best way to achieve this is by allowing farmers to participate in policy formulation and decision making.
Process and modelling studies in forest hydrology.
(1995) Summerton, Mark John.; Schulze, Roland Edgar.
The demand for timber products in South Africa, and consequently afforestation, is increasing. There exists, however, abundant experimental evidence that trees utilise more soil water than other dryland crops. Because water is limited in South Africa, decision makers therefore currently face the challenge of determining a socially, and economically acceptable afforestation management plan to enable the reconciliation of increased timber demand with scarce water supply. This challenge, and the subsequent decisions that need to be made, may be accomplished by making use of suitable simulation models to predict the impacts of the forest hydrological system on water resources. Currently, these impacts are assessed through an Afforestation Permit System (APS) which is based on a model now acknowledged to have become outdated. In this dissertation an enhanced ACRU Forest Decision Support System (FDSS), now called the ACRU Forest model, is developed and proposed as a tool for modelling forest hydrological impacts on water resources. Research for this study included a literature survey, fieldwork at two locations, viz. at forest irrigation trials at Mkuze in northern KwaZulu-Natal, and at forest site preparation trials near Ugie in the Eastern Cape, as well as the evaluation, for purposes of model development, of a series of workshops. Results from the fieldwork experiments show that large tree water use potentials are possible if water is not limiting, although a water supply threshold exists at about 1400mm.annum-1, above which diminishing growth returns occur. Furthermore, trees display improved growth on more intensive forest site preparations, but at the expense of higher water usage rates. A series of workshops which had as the main objective the extraction of expert knowledge by stimulating responses to prepared questions and by constructive discussion on relative issues pertaining to forest hydrological modelling, yielded valuable information. This information, together with that gleaned from the literature, the fieldwork and a new Quaternary catchment database for South Africa, was used to develop the ACRU Forest model. The PC-based ACRU Forest model has the potential to aid decision makers by providing an initial indication of the impacts of afforestation on water resources, within a matter of minutes. An example of the model's application is used to demonstrate its operation, relative accuracy and its potential benefits in simulating hydrological responses to afforestation.
Issues pertaining to cane supply reliability and stockpiling at the Umfolozi sugar mill - model development and application.
(2011) Boote, Gordon L. N.; Bezuidenhout, Carel Nicolaas.; Lyne, Peter William Liversedge.
The co-owned Umfolozi Mill area has developed as an integrated supply chain. Cane supply reliability was identified as a potential area for productivity improvement at Umfolozi. It is important that the cane supply to a sugar mill arrives at a steady and reliable rate. A reliable cane supply ensures that the mill can operate at an optimum efficiency. Sugarcane supply reliability depends on how the mill area adapts to unforeseeable changes in the supply chain. An important aspect to this is the weather and how it affects the harvesting regimes. The sugarcane supply chain at Umfolozi is divided into two branches, road transport and tram transport. The trams account for 70 % of the cane delivered to the mill and the can is sourced from a climatically homogenous region. In the occurrence of a rainfall event of above 5 mm, infield harvesting cannot take place on the Umfolozi Flats; hence 70 % of the mill‟s supply is halted for one or more days. To address the problem, a stochastic model was created to simulate the effectiveness of an enlarged cane stockpile if it were maintained on the current tram sidings outside the mill and were crushed when wet weather prevented further harvesting. The stockpile was simulated on a first-in first-out principle and was able to supply the mill with enough cane to continue running for 24 hours. The model was then used to conduct a series of Monte Carlo simulations on which sensitivity analyses and economic feasibility assessments were carried out. Results show that the stockpile was effective in reducing the length of milling season and the number of no-cane stops. However, on further analysis into the implications of creating a stockpile it was found that 1% recoverable value (RV) was lost during the 24-hours that the cane is stored outside the mill. The loss in revenue as a result of the RV reduction had a negative impact on any savings created with the implementation of the stockpile. This result made apparent the negative impact of deterioration to the whole supply chain. Further research is required to determine more accurately the rate of deterioration, and therefore, quantify more accurately the losses that occur in the supply chain. A significant outcome of the study was the development of a mechanistic tool which drove decision making at Umfolozi Sugar Mill. It lead to the development of the modelling framework LOMZI, a simulations based framework which places more emphasis on environmental factors and risks.
The development and evaluation of a radio frequency identification based cattle handling system.
(2013) Mutenje, Tendai Justin.; Smithers, Jeffrey Colin.; Simalenga, T. E.
Manual cattle handling systems are widely used in South Africa. A literature review and consultations were conducted with both producers and equipment manufactures, to assess the advantages and disadvantages of various cattle handling systems with the objective of developing a more efficient system that incorporates automation, electronics and Radio Frequency Identification (RFID) technology. In this study an automated, selective sorting (RFID) based cattle handling system was developed and assessed as an alternative to the widely adopted conventional manual management system practiced in South Africa. The system is still under research and not yet available on the market. This document describes the research and development process undertaken which included planning, literature review, consultation, design, fabrication, evaluation and discussions. The RFID based system developed consists of manual, semi- and fully automated components in the form of a neck-body clamp with through access, flow control double split gates and a weigh-identification-sort system. For the ease of comparison the system was developed with a manual by-pass as a control to compare the automated and manual systems in terms of establishment cost, handling duration including identification, weighing and sorting, and operator and animal stress levels which impact on business profitability and system efficiency. Both the manual by-pass and automated RFID-based systems were evaluated. The automated system resulted in reduced handling duration, operational costs and handling stress on both operator and the animal whilst enabling selective automated sorting. The infrastructure was designed to have a capacity to handle 500 animals per day with 5 handlers and a capital investment of R200 000 was required with an operational cost of R25 000 per month. After incorporating RFID, electronics and automation of the system it was established that, on average, cattle handling duration was reduced by 63%, incorrect sorting was reduced by 5.5%, man hours were reduced by 70% with 23% and 14% less fatigue and stress levels to the handler and the animals respectively, whilst achieving efficient selective sorting. A cost benefit analysis was undertaken for both systems with the aim of assessing and determining the most profitable system. An assumption was made that the cash flow pattern remains uniform for both systems over the entire evaluation period. This revealed that the introduction of RFID based technology as an alternative to a manual based system results in an increase in business profitability by 20% and shorten the payback period by 5 years. Although there is still need to further investigate the performance parameters under different environments, it can be concluded that the introduction of RFID, electronics and automation improves the overall system technical efficiency by 32% whilst enabling efficient selective handling.
The development and assessment of a direct energy calculator for use in sugarcane production.
(2014) Boote, Darran N.; Smithers, Jeffrey Colin.; Lyne, Peter William Liversedge.; Van Antwerpen, Rianto.
The rising cost of energy coupled with an increasing awareness of Greenhouse Gas (GHG) emissions has led to a concerted effort to reduce fossil fuel Energy Use (EU) in all sectors. Sugarcane production in South Africa is dependent on fossil fuel to provide a source of energy for production. To remain commercially and environmentally sustainable, measures need to be taken to reduce EU and increase EU efficiencies of on-farm operations. The first step toward realising this is to identify and quantify energy inputs. Following on from this, total GHG emissions, also known as carbon footprint, can be estimated. The primary objective of this research is to develop an energy calculator to estimate EU in sugarcane production in South Africa. The results generated by the calculator highlight areas of high energy intensity and low energy efficiencies at three different levels of detail. Based on these results, changes in management practices and technological improvements can be made to reduce EU and carbon footprint. Case studies were used to test the functionality of the calculator. Results from the case studies show that, in irrigated sugarcane production, the harvest and transport process together with irrigation account for a majority of the total on-farm EU. For one of the case studies, an estimated 20 % saving in the total on-farm EU was identified and can be achieved if appropriate technology is adopted in irrigation practices. Less significant energy savings were realised when in-field tractor operations were optimised for best tractor-implement matching. It is envisaged that the energy calculator will help farmers minimise on-farm EU and subsequently reduce input costs and carbon footprint. It will also provide a valuable tool for researchers to benchmark and profile EU in sugarcane production in South Africa. Research focussed on the sustainable production of sugar, from the agricultural to milling phase is of high priority at present. The quantification of on-farm EU in sugarcane production will form a critical component of such research.
Comparative analysis of two greenhouse microclimates in the sub-humid climate of South Africa.
(2014) Thipe, Ellen Letsogile.; Workneh, Tilahun Seyoum.; Odindo, Alfred Oduor.; Laing, Mark Delmege.
Development of small-scale greenhouse facilities that are suitable for the southern African agro-climatic conditions is one of the options that can be adopted to help alleviate food insecurity and malnutrition in Southern African countries. A comparative study was undertaken to analyse the temperature and relative humidity (RH) of two types of greenhouse tunnels, namely, the fan-pad evaporatively-cooled (FPVT) and the open-ended naturally-ventilated tunnels (NVT). The effect of the microclimates on crop growth, yield and quality, using tomatoes during the summer months and lettuce in winter, were also investigated. The effects of the integrated agro-technologies involving greenhouse microclimate and storage conditions on the postharvest quality of four tomato cultivars was also studied. The daytime temperature was lower in the FPVT than in the NVT during both summer and winter periods. Night-time temperatures were not significantly (P>0.05) different. The RH was higher in the FPVT than in the NVT, both during the day and at night. There was also a marked vertical and horizontal variation of temperature and relative humidity. Tomato vegetative growth was significantly (P<0.05) higher in the FPVT, but there were no significant (P>0.05) differences in the total yield and the total marketable yield of tomatoes grown in the FPVT and the NVT. However, the total yield was 24% higher in the NVT, but the total marketable yield was 8.3% higher in the FPVT. Highly significant (P<0.01) cultivar differences were observed, with Bona performing the best in terms of total yield and total marketable yield under both NVT and FPVT microclimates. During winter, there were no significant (P>0.05) differences in the growth and yield of lettuce crops resulting from the effect of the microclimate, although there was a higher incidence (by 26.9%) of leaf tip-burn in the FPVT. Between the two lettuce cultivars, growth was faster and the yield was 11.5% higher for Ballerina than for Nadine. However, Ballerina also had 24 to 29.6% more leaf tip-burnt leaves than Nadine. The integrated agro-technology study involving pre-harvest and postharvest treatments, which included the effect of greenhouse microclimate and postharvest storage environmental conditions on the texture, colour, TSS and pH of the four tomato cultivars, had significant (P>0.05) effects. NVT-grown tomatoes had and retained a firmer texture (by 7.4%) for a longer period, had a higher TSS value (by 10.3%), but a more rapid colour change, from mature-green to red-ripe, than FPVT tomatoes. Among the four tomato cultivars, Bona was the least firm and changed colour from green to red more rapidly, but it had the highest TSS and acidity than of the other three cultivars. With cold storage conditions at 13°C and 85% RH, the firmness of Bona was improved by 24.1% and the colour changes were reduced by 18.6%, compared to those under ambient air conditions (23± 2°C and 52± 4% RH). The cultivars Star 9037 and Star 9009 had the highest firmness and changed colour the least, but had the lowest TSS and highest pH values. This study has provided information about the microclimate of two types of greenhouses and their performance, in terms of the effects on growth, yield and quality of four tomato cultivars in summer and two lettuce cultivars in winter. The microclimate in the FPVT encouraged vegetative growth and improved the quality of the tomatoes. In the NVT, although the total yields were higher, the higher temperatures and insect/pests reduced the quality of the tomatoes. In winter, although the daytime temperatures were higher in the NVT, lettuce growth was not negatively affected, whereas in the FPVT, high humidity resulted in lower quality lettuce. The study also provided information on the integrated agro-technologies, involving greenhouse microclimate and postharvest storage environmental conditions on the postharvest quality attributes of tomatoes available on the South African market. NVT-grown tomatoes need cold postharvest storage, to reduce the ripening, in terms of colour, whereas FPVT grown tomatoes need cold postharvest storage conditions, in order to maintain a firmer texture for a longer period. It has also shown that the selection of the most suitable cultivar is important for profitable cultivation of vegetable crops in greenhouses. The study has further shown that small-scale naturally-ventilated greenhouses can be used for commercially-oriented agriculture to produce crops, with the aim to reduce poverty, create employment and address malnutrition. In addition, the study has shown that there is a need for further research aimed at reducing the daytime heat load of the greenhouses during the summer months, and the night-time heat loss during winter and a cost-benefit analysis, to establish the cost of production associated with the two tunnels. Furthermore, greenhouse microclimate research can be extended to the other South African climatic regions, to provide extensive information about the performance of these facilities and their effects on other greenhouse crops such as peppers and cucumbers.
Evaluation of systems to harvest, process and transport sugarcane biomass.
(2015) Rees, Bryan.; Smithers, Jeffrey Colin.; Lyne, Peter William Liversedge.; Van Antwerpen, Rianto.
One of the problems facing the world today is the fact that fossil fuel reserves are declining and, as a result, petrol and diesel costs are increasing. For the past century, fossil fuels have been the primary fuel source for most countries around the world and this has had an impact on the environment. This has resulted in the South African government, in line with international trends, investigating alternative energy sources to supplement and meet an increasing demand for energy. Biomass (e.g. leaves of sugarcane, referred to as sugarcane residue) is receiving increasing attention, as it is a sustainable and environmentally-friendly source of renewable energy. In South Africa, the majority of the sugar industry manually harvests burnt sugarcane. Thus, innovative residue recovery systems need to be developed to accommodate the manual harvesting of green/unburnt sugarcane. In this document, sugarcane residue refers to green/wet and brown/dry leaves, tops and green leaves constitute green residue, brown leaves constitute dry residue, and bagasse is the pulp left after the juice has been extracted from the sugarcane stalks. The name ‘residue recovery route’ encompasses both green and dry residue as, although ideally dry residue is collected, some residue recovery routes collect green residue in addition to dry residue. The objectives of this study are: (i) to assess the potential energy available from dry sugarcane residue, taking into account the benefits of leaving a residue blanket in the field, and (ii) to investigate the harvesting systems, energy and costs required to recover the residue and deliver it to a mill for both new production and harvesting systems and systems currently used in South Africa, which range from manual harvesting to fully mechanised systems. Current residue recovery methods, as well as potential methods which are still under development, are reviewed in this document. A costing model has been adopted and further developed, with the objective of estimating the costs incurred by residue collection and transport. The different residue recovery routes, which were identified in the literature review, were incorporated into the model. These routes include different methods of harvesting, residue separation infield or at the mill, the method of residue collection, residue processing and the transportation of the residue. Processing to increase the bulk density of the sugarcane residue prior to transport has been considered in this study, as its low bulk density has been identified as a critical issue in other studies. By processing the residue, the energy density and bulk density of the residue can be increased, which, in turn, improves the transport efficiency. Problems encountered when modelling residue processing included estimating the capital cost requirements, as well as the maintenance and operating costs, for each processing plant. The model was applied to two case studies, in order to compare the costs for each individual residue recovery route. This enabled the lowest cost and appropriate residue recovery route to be identified for the case studies. The cost per unit energy was used to compare the cost of the residue recovery to the cost of coal at the mill, which is required to determine whether sugarcane residue is an economically-viable source of renewable energy. Based on the assumptions made for the lowest cost routes which were identified, it was found that the cost of the residue recovery i.e. the cost of the residue, was less than that of coal and, thus, these routes are potentially economically beneficial for the mill.
Assessment of the performance of small-scale water infrastructure (SWI) for multiple uses in Nebo Plateau, Sekhukhune District, South Africa.
(2015) Sambo, Doctor Calvin.; Senzanje, Aidan.
South Africa is ranked the 30th driest country in the world and water is regarded as a scarce resource in the country. Limited availability of good quality water has resulted in urban areas receiving more water at the expense of rural areas. This is due to the fact that urban areas have a more reliable and well-maintained water infrastructure, while rural communities use unreliable and dysfunctional small-scale water infrastructure (SWI). Enhancing the performance of SWI (which are technical hardware used by rural communities to supply water for their day-to-day activities such as domestic, irrigation and rural development) used by the rural communities can enhance their rural livelihoods. The SWIs are designed and operated either as single use systems (SUS) that cater for only one water-use or multiple water systems (MUS) that cater for more than one water-use. These SWI are usually dysfunctional due to a number of reasons. Investment into SWI development, operation and maintenance (O&M), rehabilitation and modernization is limited by the lack of knowledge of the types of SWI in a given area and their functional status. This study sought to assess the performance of SWI in Nebo Plateau, Limpopo Province, South Africa by (a) identifying their types, distribution, ownership, water-use and status using a survey tool administered to the rural communities, (b) assessing their condition using modified technical and risk of failure evaluation tool, (c) investigating their causes of failure using a qualitative research approach and network analysis, and then (d) propose best management practices (BMPs) that are specific to the study area. The study found 202 SWI, which comprised of the following: unequipped boreholes (59%), equipped boreholes (hand pumps (10%), electric-driven pumps (6%), diesel-driven pumps (1%) and windmills (4%)) and small reservoirs (11%). The overall water uses were 65% SUS, 22% MUS and 13% other. The government owned 54% of the SWI, communities owned 22%, private sector owned 11%, and schools owned 2%. The government was responsible for the maintenance of 49% of the SWI. It was found that 71% of the identified SWI were nonfunctional It was found that windmills had minor defects and met rural community needs above satisfactory level. On the other hand, small reservoirs and hand pumps required major maintenance and benefited the rural communities below the minimum level. The major causes of failure were found to be lack of proper operation and maintenance (O & M), lack of O & M strategies, inadequate funds, no monitoring strategies, lack of technical skills at municipality and community level, and lack of strong leadership from the policy regulating institutions, Water Service Authority, water service provider and rural communities. It was proposed that for improved water supply to the rural communities of Nebo Plateau, there was a need to decentralize the current District municipality water service providers (WSP), establish Village Water Committees (VWC) in the rural communities, link policy with technology used, consider the effects of environment on technology, ensure availability of spare parts locally, provide technical training for both WSP and rural communities, and allocate funds for operation and management of the SWI. The study concludes that there are different SWI used by the rural communities in the study area and operated as SUS and MUS. The rural communities used water mainly for domestic and irrigation of back yard gardens. Water from small reservoirs was mainly used for livestock watering. The government owned most of the SWI and were also responsible for their maintenance. Most SWI assessed during this study were non-functional thus depriving rural communities of improved standards of living. The factors that caused the poor performance of SWI were interdependent and resulted mainly from the lack of strong institutional capabilities. The proposed BMPs were suitable for the rural communities of Nebo Plateau. It is, therefore, recommended that stakeholders involved in SWI management use the information on the status of SWI presented in this document to address areas with poor performing SWI and adopt or apply the proposed BMPs to improve their performance.
Modelling sugarcane quality in the context of mill scale supply chain logistics.
(2014) Jenkins, Edwin Peter Garland.; Bezuidenhout, Carel Nicolaas.; Ortmann, Gerald Friedel.
The length of milling season (LOMS) refers to the length and timing of sugarcane crushing operations at a sugar mill. LOMS is central to the competitiveness and profitability of any sugar mill supply area (MSA). Conflicting interests between supply chain stakeholders can make adjusting the LOMS difficult. The LOMS should take into account weather conditions, cane quality, milling capacity, supply chain capabilities and other interrelated issues, such as agronomics. Previous LOMS models in South Africa were developed over a decade ago and there was scope to improve the calculation of risks by using a stochastic modelling approach. Recently, a stochastic model named LOMZI was developed to evaluate stockpiling options at Umfolozi. In this study, LOMZI was adapted and expanded to allow the LOMS for any MSA in South Africa to be investigated. However, mill area specific applications of the updated model fell outside the scope of this study. As it currently stands, LOMZI simulates a sugarcane supply chain from the point where sugarcane is cut, up to delivery at the mill. During the process of adapting LOMZI, the simulation of sugarcane quality was identified as an important area for improvement in the model and this became the focus of the study. A predictive MSA scale cane quality model was developed, based on recent weather conditions and a mechanistic understanding of sugarcane quality. The quality model was developed to simulate the daily average brix %, pol % and fibre % of sugarcane delivered to the mill. The preceding 11 weeks’ rainfall and temperature values were used to predict cane quality. A total of 98 mill-specific coefficients were calibrated from historic milling data and, for model demonstration purposes, the quality model was applied at two mills, namely Sezela and Umfolozi. Independent verifications yielded R2 values between 0.56 and 0.74. A useful method to estimate the average burn/cut to crush delay for a MSA was also identified. The quality model has been successfully integrated with LOMZI. Future work is envisaged to expand LOMZI and to model the operations of sugar mills and the RV cane payment system.
Infrared drying of biltong : effect of pre-treatment and drying conditions on the drying characteristics and product quality.
(2014) Cherono, Kipchumba.; Mwithiga, Gikuru.; Workneh, Tilahun Seyoum.
In this study, the drying kinetics of biltong was investigated under infrared and convective drying systems, with two product pre-treatment conditions namely, slice thickness and marinating duration. The effect of these treatments on the quality and microbiological food safety of biltong was investigated. In addition, the study sought to establish and compare the energy efficiencies of the infrared drying systems under investigation. The drying of biltong was conducted under two infrared drying conditions (2.5 μm and 3.5 μm peak wavelengths) and a convective drying condition that mimicked conventional and commercial drying conditions at a temperature of 25°C and 60% relative humidity. The two infrared heating systems were set so that they had the same intensity of 4777 W.mˉ² at the product surface, but different peak wavelengths (2.5 μm and 3.5 μm). The marinated products were dried from a moisture content of 73.99% ± 1.46% wet basis (wb) to the commercial quality requirement of 20% ± 1% wb. Samples had a product thickness of 5, 10 or 15 mm, and had been marinated for durations of 6, 12 or 24 hours prior to drying. The experiments were arranged in a complete randomized block design. The drying rate, product temperature, quality attributes, such as colour, texture, shrinkage, rehydration, as well as total viable bacterial counts were measured, along with the infrared power consumption during the drying process. It was observed that the infrared heater with a peak wavelength of 2.5 μm dried the products faster, when compared to the one with a peak wavelength of 3.5 μm at all times, even when the infrared intensity of both heaters on the products was the same. The convective drying system recorded lower drying rates and longer drying durations compared to the infrared heating systems. Increasing product thicknesses increased the drying times and reduced the drying rates for samples dried under the 2.5 μm peak infrared heater and the convective drying system. Increasing the duration of marinating, reduced the drying rates for samples dried under the convective air dryer and increased the drying rates for samples that were dried under the 2.5 μm peak infrared heater. The 3.5 μm peak infrared heater recorded varied results, but generally had the 10 mm thick and 12-hour marinated samples having higher drying rates for all samples dried under this system. The drying system used significantly (p≤0.05) affected the drying times, while the pre-treatment conditions had no significant (p≥0.05) effect on the drying times. The core temperature increased with decreasing product thicknesses and increasing marinating duration for the 2.5 μm peak infrared heater. However, the 3.5 μm peak infrared heater product core temperature did not follow the same trend. This system recorded lower specific energy consumption (SEC) values, compared to the 2.5 μm peak infrared heater. Out of the five drying models tested, the drying kinetics of biltong was best described by the approximation of diffusion model (ADM) on the basis of the model’s high coefficient of determination (R²) and low root mean square error (RMSE) values. The sample lightness (L*) of dried samples was significantly (p≤0.05) influenced by the drying system. The convective air drying system recorded lower total colour difference (ΔE) values compared to the infrared systems. The L* a* b* colour parameters decreased after marinating fresh beef slices, and decreased even further after the drying process. Textural analysis showed lower hardness and puncture values for samples dried under the 2.5 μm peak infrared heater compared to the other drying systems. Samples dried under the 3.5 μm peak infrared heater recorded the highest shrinkage coefficient and rehydration rates. The three drying systems achieved at least a 2-log reduction in the total viable bacterial count, with the 2.5 μm peak infrared heater having the lowest most probable number (MPN) count of 7,020. The infrared drying systems produced biltong that had acceptable plate counts of E-coli less than 10² CFU.g⁻¹. However, the convective air drying system did not meet this acceptability threshold for the safe consumption of biltong. The samples that were dried under the 2.5 μm peak infrared heater recorded high drying rates, good microbiological safety and textural attributes compared to the convective and 3.5 μm peak infrared drying systems. However, this system had consumed more energy compared to the 3.5 μm peak infrared heater that produced biltong with superior shrinkage coefficient and rehydration characteristics as well as colour attributes that closely compared to those of samples dried under the convective air drying system. The study recommends both the 2.5 and 3.5 μm peak infrared heaters for the best texture of biltong, improved drying characteristics and enhanced microbial food safety of the product.
Improvements to the functionality of the mycanesim® irrigation scheduling advice system for sugarcane.
(2016) Paraskevopoulos, Aresti Lambros.; Singels, Abraham.; Senzanje, Aidan.
MyCanesim® is a web-based crop simulation system that can be used for irrigation scheduling and yield estimation. Two shortcomings of the system identified were that 1) advised irrigation amounts could exceed seasonal water limitations imposed on farmers and 2) simulations are only accurate if farmers follow the recommended irrigation actions and if simulated and actual available soil water content are similar. These can be addressed by incorporating algorithms for optimal scheduling of limited water, and by making use of soil water content measurements in model simulations. The objectives of this study were to 1) evaluate the performance of different optimization algorithms that schedule limited water and 2) determine the accuracy of irrigation scheduling advice and cane yield estimates with and without adjustment of simulations with soil water content records. Four irrigation scheduling algorithms were tested against a baseline algorithm, using 960 hypothetical scenarios consisting of different water supply, climate and cropping situations. These were: (a) Crop stage, which accounts for the yield sensitivity to water deficit as it varies with growth stage; (b) Stress level, which evaluates different soil water depletion levels for determining irrigation dates; (c) Prorata, which reduces irrigation throughout the growing season in proportion to the seasonal allocation shortfall; and (d) Water satisfaction, which iteratively schedules irrigation events on the day with the largest water demand. Algorithms increased simulated yields over the baseline by between 4.7 and 8.6 t/ha on average and operated at computational running times of between 1 and 40 s. The stress level algorithm was recommended for inclusion into MyCanesim®, since it had both a high yield improvement (8.5 t/ha) and quick operational time (2.5 s). Soil water measurements from capacitance probes for thirteen fields in Mpumalanga were integrated through an automated process into the MyCanesim® system. The improvements in the accuracy of irrigation scheduling advice and yield estimates by the integrated system were assessed retrospectively. The integrated system resulted in more accurate irrigation scheduling advice (by 2 days) than weather-based scheduling alone. These two improvements to MyCanesim® should allow sugarcane farmers to achieve higher irrigated water use efficiency and yields because of more accurate irrigation scheduling advice and yield estimates for full and restricted irrigation water supply.
The effects of precipitation on the sugarcane supply chain of Sezela and Umzimkulu.
(2015) Dzapatsva, Precious.; Lyne, Peter William Liversedge.; Lagerwall, Gareth.
Abstract available in PDF file.
The effect of bioslurry, grass clippings and pumpkin live mulch on soil water content and maize production.
(2016) Ngubo, Nelile.; Odindo, Alfred Oduor.; Everson, Theresa Mary.
Abstract available in PDF file.
Evaluation and modelling of different greenhouse microclimates under South African agro-climatic conditions.
(2016) Du Plessis, Erna.; Workneh, Tilahun Seyoum.; Laing, Mark Delmege.
Abstract available in PDF file.
Meeting the extension needs of smallholder farmers : the climate information gap in the public agricultural extension and advisory services in Limpopo, South Africa.
(2016) Zikhali, Zafezeka Mbali.; Mudhara, Maxwell.; Mafongoya, Paramu L.
This study examined the gap in climate information within public Agricultural Extension and Advisory Services in Limpopo. Specifically, it assessed extension officers’ climate change perceptions, climate change knowledge, and their formal and informal climate education. Lastly, the study examined the extension approaches and extension officers’ perceptions of overall suitability of the overall climate information disseminated to rural smallholder farmers. The study used a semi-structured questionnaire on 90 public extension officers purposively sampled. The Limpopo Department of Agriculture and Rural Development (LDARD) employed all the officers in two districts, i.e., Mopani (Tzaneen and Maruleng Municipalities) and the Vhembe (Musina and Mutale Municipalities). The data was analysed using the IBM Statistical Package Social Science (SPSS). Content analysis was used for analysing qualitative data, such as the likert scale data, focus group discussions and key informant interviews. The results indicated that participants were predominately male, between the age groups of 31-59 years, and possessed B. Tech/Degree qualifications. Women extension officers were slightly more educated than males. Extension officers’ climate change awareness was average. Education levels had an influence on exposure to climate education, in-serve and climate change training and extension approaches used to disseminate agricultural information to client farmers. They also acknowledged that the climate change information disseminated to smallholder farmers was not suitable for their needs. The study concluded that extension officers need to keep abreast with climate change knowledge through continuous retraining. There is also a need to integrate indigenous knowledge to climate information to increase the suitability and acceptability of the information by smallholder farmers.
Evaluation of the effects of supply chain routes and pre-storage treatments on the postharvest quality of stored 'Nemo-Netta' tomatoes.
(2016) Shezi, Sabelo.; Workneh, Tilahun Seyoum.
Tomato postharvest losses are the major constraints that limit optimum competitiveness and marketability of tomatoes. This becomes a serious threat since tomatoes are highly perishable, and lose quality at any stage of the supply chain. In this study, the effects of supply chain routes, pre-storage treatments and storage conditions on microbial quality were evaluated in ‘Nemo-Netta’ tomatoes harvested at pink maturity stage. The effects of supply chain routes, harvesting maturity stages, pre-storage treatments, pre-storage treatments, and storage conditions on physiological, biochemical and chemical quality of ‘Nemo-Netta’ tomatoes were also evaluated. The study also evaluated the combined effects of integrated postharvest technologies. The effect of disinfecting tomatoes with different solutions (anolyte water, chlorinated water and hot water) or coating tomatoes (with Gum Arabic), on the microbiological quality of tomatoes during storage after transportation in non-refrigerated trucks along three different supply chain routes was evaluated (Chapter 3). Upon the arrival of tomatoes in Pietermaritzburg market, they had condensed droplets on the fruit surfaced which was speculated to be due to the differences in temperatures and relative humidity within truck during transportation. Droplets on the fruit surface became a conducive environment for microorganisms to proliferate. Pink-matured tomatoes with freedom from blemishes were treated, stored on either ambient (16 °C in winter / 25 °C in summer) or cold (11 °C), and sampled on day 0, 16 and 30 for quality assessment. An experiment was laid out as a factorial split-plot design with supply routes as main plots, storage conditions as subplots and random allocation of treatments within each subplot. An experiment was conducted in two seasons during winter harvest and during summer harvest. The results revealed a highly significant difference (P < 0.001) in the microbiological population (log cfu cm-2) and marketability (%) of tomatoes from different supply routes, storage environments, and treated with different disinfectants. Anolyte water was the most effective treatment in maintaining quality of tomatoes. It reduced the initial microbial load significantly (P < 0.001) to 3.779 log cfu cm-2. This represented the second highest log reduction of 1.049 log cfu cm-2 when compared to untreated control which had 4.828 log cfu cm-2. Furthermore, three-way interaction of supply route, disinfectants, particularly anolyte water with low temperature storage remained the most superior treatment in the microbial quality of pink-matured tomatoes. It reduced the initial microbial load significantly (P < 0.001) to 2.835 log cfu cm-2. This represented the highest log reduction of 1.470 log cfu cm-2, when compared to untreated samples. Anolyte water also maintained the highest percentage of the general marketability of pink-matured tomatoes, however a three-way interaction of supply route, disinfectants, particularly anolyte water with low temperature storage remained the most superior treatment in maintaining marketability of pink-matured tomatoes across all the supply routes. The effect of disinfecting tomatoes with different solutions (anolyte water, and hot water) or coating tomatoes (with Gum Arabic), and their combinations on the physiological, chemical and biochemical quality of tomatoes during storage after transportation in non-refrigerated trucks along three different supply chain routes was evaluated in Chapter 4. Green, pink and red matured tomatoes with freedom from blemishes were treated, stored on either ambient (16/ 25 °C) or cold (11 °C), and sampled on day 0, 8, 16, 24 and 30 for quality assessment. An experiment was laid out as a factorial design, split-split plot with supply routes as main plots, maturity stages as subplots, storage conditions as sub-subplots and random allocation of treatments with each subplot. An experiment was conducted in two seasons during winter harvest and during summer harvest. The results revealed highly significant impact (P < 0.001) of individual technologies in maintaining quality, which was measured by number of parameters including colour, texture, TSS, physiological weight loss, respiration rate, total phenolic compounds, Total antioxidant capacity and general marketability. Furthermore, integrated technologies had more superiority in maintaining quality of tomatoes. Therefore anolyte water and Gum Arabic coating need to be researched further as potential substitutes of chemical treatments that are currently used by tomato industry.
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 MJ.mm.ha-1.h-1 vs. 16 399 MJ.mm.ha-1.h-1). 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.
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.
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.
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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