Irrigation with brackish water under desert conditions VI. Automated systems to produce a range of salt concentrations in irrigation water for experimental plots

Abstract

This paper describes three different systems developed recently in the Negev desert to enable the carrying out of both small- and large-scale field trials on irrigation with brackish and saline water. All three systems are fully automated. The first system, called the mixing junction, was designed to supply to the field relatively large quantities of water with a predetermined, constant salt concentration, when the salinity level of the water source at the field head may vary. The system has an electrical conductivity (EC) sensor inserted after the mixing junction and connected to an electronic logic circuit that operates hydraulic valves for brackish and fresh water in opposite directions to obtain the desired EC level. The second system, called the brine injection system, was developed to produce a range of salt solutions for field studies of salinity when the major water source is of a low and constant salinity level. The system is based on the injection of different amounts of brine simultaneously into several irrigation lines with a water-driven fertilizer pump, through a series of water flow regulators. The third system, called the mixing manifold, was developed to dilute an abundant source of water having a high and constant salinity level with fresh water, to obtain a range of salt concentrations in the irrigation water. The two water sources pass through parallel flow regulators and are mixed at the outlet of the regulators. Water flow through the regulators is controlled by an irrigation computer. All these systems have been operating successfully for periods of from 2 to 5 years.