investigation of infiltration in center pivot irrigation system

use of the double ring infiltrometer to measure soil water infiltration in center pivot irrigation systems is not an accurate approach; because the real conditions of infiltration under center pivot sprinklers is different from what happens in the double ring. in this study, the infiltration parameters were determined under real conditions of a center pivot system. for this purpose, a single ring with drainage equipment was used which could measure both infiltration and runoff rates during the experiments. field tests were carried out at agricultural research station of tabriz university, where soil texture was sandy loam. treatments of the experiments were two types of sprinkler (ldn, i-wob), three operation pressures (15, 20, and 25 psi), and two sprinkler heights (1.6 and 2 meter) with three replications. the results showed that the average amounts of infiltration rate and cumulative infiltration in the double ring method were double of the mentioned amounts in the single ring method. therefore, use of the double-ring method data in design phase causes a significant runoff in operation. the maximum amounts of infiltration rate and cumulative infiltration were obtained in irrigation with operation pressure of 25 psi and sprinkler height of 1.6 meter. the model of kostiakov had the maximum coefficient of determination (r2) and the model of green and ampt had the minimum amount of standard error (se) in fitting with the measured infiltration data under real condition of a center pivot system in the field.