This is because they have not appreciated the difference between the average moisture content and the local and temporary moisture content within the root zone. Once the system has detected a need for irrigation, the next step is to determine the irrigation schedule. This would require a continuously varying flow rate throughout the day. In practice, however, irrigation systems can only supply water at a fixed rate, so matching the irrigation supply to a plants needs is achieved by varying the irrigation times. Response times with different irrigation systems.
All irrigation systems have minimum and maximum irrigation times.
The minimum is the time it takes water to start being effective in irrigating all areas. The maximum is the time which coincides with water just reaching the lower limit of the root zone. Any water passing the root zone of a plant is essentially lost and this should generally not be permitted to happen. To further illustrate response times, let s now consider a sprinkler system. To begin with, there will be a series of delays from turning the water on, to the point where the water reaches the root zone.