To demonstrate the influence of the diesel engine’s speed over the energy consumption and performance of large lateral move (LM) irrigation machines, 10 field tests were conducted on four LMs on the Darling Downs of South East Queensland. A key objective of the research was to identify if a relationship existed between the performance (uniformity) and energy consumption of the machines, allowing an optimum point to be established.

The main findings of the field testing and analysis were: 1) in general, the emitter discharges were found to decrease with increasing distance from the supply pump; 2) the uniformity was found to decrease in all cases when the engine speed decreased the total flow rate below that of the design; 3) the energy consumption increased with each increase in engine speed; 4) the energy consumed per ML of water pumped, and hence energy cost per year, increased significantly with each increase in engine speed; and

5) a relationship was found to exist for two of three LMs whereby the highest uniformity was achieved at engine speeds that put the pump operating point closest to that of the design.