The duration a sprinkler should run is not a fixed number of minutes but a variable calculation based on two factors: the capacity of your soil to absorb water and the rate at which your specific sprinkler delivers it. Effective watering aims for deep root saturation rather than simply wetting the surface. By understanding both the ground’s needs and the system’s output, you can create a precise, water-efficient schedule.
Understanding Your Soil’s Capacity
The composition of your soil dictates how much water is needed and how quickly it can be absorbed. The goal of deep irrigation is to moisten the soil to a depth of four to six inches, where the majority of healthy turfgrass roots are concentrated. Sandy soils drain quickly due to large pore spaces and require shorter, more frequent watering sessions. Clay soils absorb water very slowly but hold it longer, though they are highly prone to runoff if water is applied too quickly.
Measuring Water Application Rate
Before determining a run time, you must calculate your sprinkler’s water application rate, measured in inches per hour, using the catch cup test. This procedure requires six to ten straight-sided containers, such as tuna cans, and a ruler. Place the containers randomly within the spray pattern of the sprinkler zone. Run the sprinkler for a fixed duration, such as 15 minutes, and measure the water depth collected in each can. To find the average application rate in inches per hour, average the depths collected and multiply that average by four.
Calculating the Ideal Watering Duration
The final step is combining the required water depth with the sprinkler’s application rate to calculate the total run time. For deep watering, the typical goal is to apply one inch of water to soak the root zone. The formula for total run time is the target water depth divided by the application rate. For instance, if the application rate is 0.5 inches per hour, applying 1.0 inch of water requires a total run time of 120 minutes.
The Technique of Cycle and Soak
Applying the total calculated duration all at once often leads to significant water waste because the soil’s infiltration rate is slower than the sprinkler’s application rate. The cycle and soak technique solves this by breaking the total time into two or three shorter intervals. Run the sprinkler for a short cycle, such as 15 or 20 minutes, until runoff begins, then allow a soak period of 30 to 60 minutes for the water to infiltrate the soil. After the soak period, resume watering for the remaining calculated time to ensure efficient, deep application.