Browsing by Author "Lecler, Neil Louis."

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A framework to improve irrigation design and operating strategies in the South African sugarcane industry.
(2009) Jumman, Ashiel.; Senzanje, Aidan.; Lecler, Neil Louis.
The purpose of this study was to develop a framework to assess irrigation design and operating strategies. This objective was achieved successfully and the framework was applied to formulate guidelines to increase farm profitability whilst using scarce resources, such as water and electricity, effectively. The study was targeted at sugarcane irrigated with semi-permanent irrigation systems. “ZIMsched 2.0”, a water balance and crop yield prediction model and the “Irriecon V2” economic assessment model were available at the start of the study. The missing link, however, was a relatively cost effective and efficient method to design and cost irrigation hardware alternatives. Irrigation hardware impacts on both the agronomic and economic performance of systems, for example, through different peak design capacities and associated operating limitations. Thus, a novel, spreadsheet-based irrigation design tool, with an automated costing component, was developed to complete the framework. The framework was used to investigate the costs and benefits of potential design and operating solutions to a selection of irrigation issues, including: over-irrigation on shallow soils, the opportunity to shift electricity use out of expensive peak periods and, the opportunity to demonstrate the benefits of deficit irrigation strategies. For shallow soils, the increase in system hardware costs, needed to better match water application to soils, increased margins due to more effective water use. Innovative deficit designs and operating strategies allowed for reductions in water and electricity costs. The reduced costs, however, did not always offset yield penalties and revenue loss resulting from water stress. The financial benefits of deficit irrigation strategies were shown when water savings were used to convert dry land cane into irrigated cane. This highlighted the differences between the direct and opportunity costs of water. Finally, a field work component, relating to the precise monitoring of irrigation strategies and corresponding crop responses was included in this study. Systems which enabled soil water potential and stalk extension to be monitored remotely via the internet were considered useful for the successful implementation of an optimum irrigation strategy. The easily accessible data allows for effective decision making and more importantly, reassures famers of the current state of their crop.
Development and assessment of an automatic short furrow irrigation system.
(2010) Mills, D. D.; Lecler, Neil Louis.
Automated short furrow irrigation (ASFI) is a prototype irrigation system that has the potential to be robust and relatively low-cost, with highly effective and efficient water use. ASFI has low energy requirements because the pressure at the field edge is relatively low, typically 70 kPa (or 7 m) as compared with approximately 150 kPa for drip and 400 kPa for dragline systems. However, at project onset, the only type of ASFI system tested was Microfurrow which was, among other problems, not robust. The aim of this project was, therefore, to develop, implement and evaluate a suitable ASFI system and to compare the system to a reference sub-surface drip (SSD) irrigation system with sugarcane as the test crop. This process resulted in the development of a boot and piston valve, which was used to automatically control the flow between specific plots. The valve was then implemented, as per design, in the ASFI system at a trial at the University of KwaZulu-Natal’s Ukulinga research farm. Irrigation events were scheduled according to SAsched with the aim of applying equivalent amounts of water to both the ASF and SSD treatments. The testing and evaluation included irrigation uniformity tests and the crop yields. Evaluation of selected furrows in the ASFI treatment showed a low quarter distribution uniformity (DUlq) range between 72 % and 80 %. This is considerably better than approximately 60 % for conventional furrow irrigation. However, the DU for ASFI could be improved to above 90 % if the slope was reduced from 1:40 to approximately 1:250. Both the harvested tons per hectare and sucrose content results were evaluated using a one-way statistical analysis with differences between the results deemed to be insignificant. Therefore, the ASFI performance in terms of harvest data for the Ukulinga trial could be described as “similar to” SSD irrigation. A 10 ha sample ASFI system was designed and compared in economic terms with a respective SSD system. Although further piping options can be explored in order to reduce the capital costs of the ASFI system even further, ASFI was considerably more cost-effective than the SSD system in terms of operating and fixed costs per hectare. The ASFI irrigation system, although having some initial maintenance requirements in insuring all furrows performed properly, required no other maintenance throughout the year in the Ukulinga trial. The drip system, however, required laterals to be flushed and leaks to be repaired. It is therefore believed that the ASFI system meets the required objectives of the project in that it is robust, low-cost (both operating and fixed) and able to supply water efficiently and effectively.
In-field evaluation of irrigation system performance within the sugarcane industry of the south-east Lowveld in Zimbabwe.
(2007) Griffiths, Bak.; Lecler, Neil Louis.; Smithers, Jeffrey Colin.
The near collapse of the Zimbabwean sugarcane industry in 1991/1992 was concluded to be as a result of critical water shortages. This, combined with the uncertainty in the availability of water and a climate characterised by recurring droughts, strongly motivated the sugarcane industry in the South-East Lowveld to strive for improvements in water management and led to the establishment of the Mobile Irrigation Performance Unit (MIPU) in April 2000. Following an extensive literature review, evaluation methods and performance parameters were determined for the different irrigation systems currently in use in the sugarcane industry within the Lowveld of Zimbabwe, in relation to international standards. The systems in use included furrow, centre pivot, hand-move sprinkler, static sprinkler and sub-surface drip. The study also resulted in the development of some novel evaluation tools, examples being a simple device to measure the inflow to irrigation furrows and a uniquely shaped nozzle, used to determine operating pressures within the sub-surface drip system. Factors that can affect a system's performance were investigated and a comparison of the different irrigation system's performance parameters was shown. The evaluation results obtained by the Lowveld MIPU were also compared to MIPU results obtained internationally and reported in the literature. The MIPU evaluations are considered to be of great benefit to the farmer because an extensive database of irrigation system performance has been collated, against which farmers can benchmark their systems in the future. It is also possible that the repetitive nature of certain management and design variables which may be detrimental to system performance under local conditions, can eventually be rendered obsolete, for example, incorrect assumptions in scheduling of irrigation. The evaluation data can also be used to help facilitate objective decisions regarding the selection of irrigation systems to suit particular environments. The research indicates that the sugarcane industry could derive major benefits in improved irrigation systems performance by ensuring that irrigation system operators have the required calibre of skills and sufficient training. The results reported here should benefit farmers and result in refinements to the crop production system rendering it more cost effective and efficient.
Performance of irrigation and water management systems in the lowveld of Zimbabwe.
(2004) Lecler, Neil Louis.; Schulze, Roland Edgar.
In order to assess the performance of water management approaches and irrigation systems used by the sugar industry in the Lowveld of Zimbabwe, a sugarcane yield and irrigation systems simulation model was developed. The model, named ZIMsched 2.0, was used to predict how field derived indices of irrigation systems performance, such as the coefficient of uniformity, CV, impacted on estimated recoverable crystal, ERC, yields and the water balance. This was done across a range of soil conditions, seasonal climates, irrigation system types and existing and refined irrigation scheduling strategies. Results of a verification study of the model showed an index of agreement, 'd', equal to 0.96 and a Pearson's correlation coefficient equal to 0.94, between observed and simulated yields of ERC, relative to a reference treatment. Application of the model showed the actual and also the potential performance of the different irrigation system hardware. Additional applications of the tools and information which were developed as a result of this research included an integrated economic assessment of peak irrigation system design specifications and associated deficit irrigation watering strategies. In an effort to translate theoretical water savings into practical realities a range of novel water management tools was also developed. Most of the drip irrigation systems in the Lowveld were performing below potential due to excessive infield variations in applied water. The performance of furrow irrigation systems was limited by the large variations in water applied to individual furrows, and water applications that were, on average, excessively high relative to soil water holding characteristics. Simulations showed that sub-surface drip irrigation systems have a slight edge on other irrigation systems in terms of potential efficiency. Average water savings for drip irrigation systems ranged from approximately 2.2 to 1.5 Ml/ha relative to floppy irrigation systems, and 3.5 to 2.3 Ml/ha relative to typical furrow irrigation systems, depending on how water applications were scheduled. A major finding was that there was potential for the Lowveld sugar industry to use up to 30% less water per hectare on an annual basis if ZIMsched, a specialist spreadsheet-based irrigation scheduling tool developed during the course of the project, was used to derive more appropriate and system specific water management guidelines. However, simulations showed that with the more precise irrigation scheduling there could be a slight crop yield penalty when the distribution uniformity of applied water was poor.
Quantifying and benchmarking irrigation scheme performance with water balances and performance indicators.
(2007) Greaves, Kevin Robert.; Lecler, Neil Louis.; Smithers, Jeffrey Colin.; Ascough, Gregory William.
South Africa is a water scarce country. As pressure on available water resources increases, irrigation, the largest consumer of water, has to find ways of improving water use efficiency. Benchmarking in the irrigation sector has been identified as a suitable technique to implement this improvement. Benchmarking can be broadly defined as the identification and application of organisation specific best practices with the goal of improving competitiveness, performance and efficiency. A South African sugarcane irrigation scheme was identified to investigate a proposed benchmarking methodology. The scheme was unique in that electromagnetic flow meters were utilised and monitored on a daily basis. This facilitated an in depth study into irrigation water use at the scheme. The project focused on three different objectives. The first objective was to determine the losses, and consequently the efficiency, with which the irrigation scheme was able to deliver irrigation water from the water source to the farm boundary during the years 2004 and 2005. This was achieved by completing the water balance for the scheme with specified geographic and temporal boundaries. Results indicated that the scheme was very efficient with a delivery efficiency of 83.4 and 94.0 % for 2004 and 2005 respectively. These efficiencies were above the accepted South African Department of Water Affairs and Forestry (DWAF) standard of 80 %. The temporal distribution of the delivery efficiency was also investigated to identify periods within each year when inefficiencies occurred, and to better understand the nature of potential losses. It was concluded that the investigations into the temporal distributions be utilised together with the water balance approach in future studies into the performance of irrigation water delivery infrastructure at other South African irrigation schemes. The second objective was to calculate a set of internationally applied external irrigation benchmarking indicators. External indicators from the International Water Management Institute (1WMI), the International Program for Training and Research in Irrigation and Drainage (IPTRID) and the Irrigation Training and Research Center (ITRC) were reviewed for application in a South African context. The external indicator analysis highlighted that at a scheme level, insufficient irrigation was occurring to effectively meet the irrigation demand. It was also found that the scheme infrastructure was not the limiting cause of this observation. The external indicator results highlighted the need for additional schemes for comparison purposes. The results from this component of the study also emphasized the importance of stakeholder confidentiality concerns when attempting to implement a benchmarking initiative. The third objective was to rank individual farm performance of all the farms in the scheme, in terms of total farm sugarcane yield and seasonal irrigation water use. Farm yield and irrigated area were obtained to investigate the relationships between yield and irrigation water application. There were substantial variations in total farm yield and water use for both the 2004 and 2005 seasons, indicating much potential for improvement by many farmers relative to each other. The individual seasonal farm water use was also compared to a simulated irrigation demand, as determined with the SAsched irrigation systems and crop yield model. Simulation results with the SAsched model, using representative soils and climate data for the scheme, showed that the majority of farms were under irrigating relative to the simulated demands, especially in the late spring/early summer period. From on-farm irrigation system evaluations that were performed, it was found that irrigation system capacity constraints were not limiting irrigation applications in the majority of farms. Further research in the form of selected soil water monitoring is required to investigate these observations further.