21
SMRT-Y Soil Moisture Sensor
Setting the Watering Schedule
Field Capacity is the amount of water your soil will hold at equilibrium. The amount of water required to bring
the moisture content of the soil from 80% of Field Capacity to 100% of Field Capacity is given by the formula:
Inches of water = 0.2 * Field Capacity * depth
If your Field Capacity is 25% and you are watering to a depth of 8 inches, then the amount of water needed
is
0.2 * 0.25 * 8 = 0.4 inches
If you know the effective precipitation rate of your sprinklers, then the watering time is given by:
Run time minutes = 60 * Inches / Effective Precipitation Rate
If your Effective Precipitation Rate for the example above is 0.5 inches per hour, then the minutes watering
time is
60 * 0.4 / 0.5 = 48 minutes.
The chart on the next page offers a simple way to set watering times for all zones in your system. It is based
on the formulas given above. After you have measured the Field Capacity of your soil (see next page), you can
use the chart to find watering times for your zones. You will need to know the type of sprinkler heads installed
and their precipitation rates.