Development and assessment of an automatic short furrow irrigation system.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

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.