Maximum length of subsurface drip irrigation laterals subjected to backpressure

Abstract

To achieve a better SDI system design, the emitters' hydraulic characteristics and the fl owrate uniformity along lateral lines under backpressure infl uence must be known. The objective of this study was to evaluate the effect of backpressure on the maximum length of irrigation laterals using two types of emitters (pressurecompensating and nonpressure-compensating) in different situations. Data from a fi eld experiment combined with information obtained from a previously published paper was used, that tested driplines hydraulics behavior infl uenced by backpressure. The lateral dripline design technique based on statistical approach developed by Anyoji & Wu 1987 was used to calculate the maximum length. The variables that most infl uenced the maximum length of the laterals were the terrain slope and permissible fl owrate variation. For nonpressure-compensating emitters, the maximum length of the irrigation laterals is up to 5% greater in subsurface applications than in surface applications.For pressure-compensating emitters operating under the infl uence of backpressure, there is an increase in the discharge exponent due to the small difference in fl owrate between the surface and subsurface conditions, which also increases the infl uence of pressure variations on the fl owrate thus, the surface laterals are up to 8% longer than the subsurface ones.

Backpressure effects on emitters flow rate in subsurface drip irrigation

“…Saefuddin et al (2019) explain that there is a relationship between soil pressure and emitter flow and, for this reason, soils with low infiltration capacity tend to decrease the buried emitters discharge, which causes variations in system flow rate. Thebaldi et al (2021) present that this behavior is due to backpressure, a phenomenon that occurs when the buried emitter water application intensity exceeds soil infiltration rate, which, according to Shani et al (1996), creates a positive pressure around the dripper and reduce the hydraulic potential gradient at the soil-emitter interface, consequently reducing the flow rate of this. Thus, the backpressure phenomenon can change the hydraulic characteristics of emitter in subsurface drip irrigation and may vary and reduce the drippers flow rate, resulting in poor irrigation uniformity (Ren et al, 2018;Thebaldi et al, 2016).…”