Assessment of two variable rate irrigation controllers used on a centre-pivot

This paper reports on the contrasting patterns of two variable rate application systems used in precision irrigation: the pulse width modulation and the bi-model sequencing, on the distribution uniformities of the two systems and on the evaluation of their performance with regard to the different low operational pressures of 1, 1.5 and 2 bar. Twenty-one tests were conducted with 90-130 measurements for each test. The two systems were tested statistically with a water diffusion plate. A pulse frequency of 3 cycle/minute operated in a duty cycle of 47-50% was used for the purpose of evaluation. The results were used to simulation three areas under the three spans of the centre pivot. The simulation was based on a single nozzle performance. The results of the different performance variables revealed that the pulse width modulation system performed more efficiently than the bi-model sequencing throughout all tests and that the pressure of 1.5 bar was the lowest pressure that gave optimal results.