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 pressured 1, 1.5 and 2 bar. Twenty-one tests were conducted with 90130 measurements for each test. The two systems were tested statistically with a water diffusion plate. A pulse frequency of 3 cycle/minute that operated in a duty cycle of 4750% was selected for the purpose of evaluation. The results were used for simulating 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 system throughout all tests and that the pressure of 1.5 bar was the lowest pressure that gave the optimal results.