Each irrigation zone can be controlled by either a manual gate or ball valve or automatically by an electric solenoid valve. Usually one valve controls one zone. Solenoid valves use a low-voltage (24 volt) electrical current that actuates a small electromagnet to hold open the valve. When the voltage is removed the valve closes.
In automated systems, solenoid valves are activated by controllers that can range from electrical timers to complex computer systems capable of complex decisions.
Moisture sensors and EC meters may be used in conjunction with controllers to to achive more sophisticated water application control in a nutrient management scheme.