Soil Moisture Sensors
Water savings of 46 to 88% reported in Florida
compared to systems with rain sensors
(Lailhacar et al., 2005)
Typical installation – solenoid
Locate Valve
3 wires
Dry area
Atypical installation – controller
Connected in controller box
Same 3 wires
Wiring
Moisture sensor Red 0 Controller hot (color wire – yellow, aqua, or other)
Moisture sensor Black 0 Valve hot (black)
Moisture sensor White 0 Controller common (white) and Valve Common (black)
Sensor Location
• 4” below ground
• Dry representative location – full sun
• Avoid driveways and sidewalks
• >3’ from sprinkler head
• Avoid low areas, bottom of hills
• Avoid high foot traffic
Install sensor in root zone
1. Install sensor (4-6” deep hole)
2. Valve box for connections
3. Water and allow it to drain – field capacity
4. Set at ~75% of field capacity
Why Soil Moisture Sensors Work
Soil Classification & Soil Moisture
Set at 75% field capacity
~30% field capacity
50
40
Plant available Water
30
PWP & Soil Matrix
20
10
SILTY LOAM
SILTY CLAY LOAM
SILTY CLAY
SILT
SANDY LOAM
SANDY CLAY LOAM
SANDY CLAY
SAND
LOAMY SAND
LOAM
CLAY LOAM
0
CLAY
Soil Moisture %
60
How many zones?
One sensor can be used to control multiple zones
Programming the
Controller
• 1 hr. irrigation
• 6 @ 10 min cycles
• 6 on/off readings
• 0,10,20,30,40,50, or 60 minutes of run time
If moisture is adequate then no irrigation
Moisture adequate after 1,2,3,4, 5 cycles –
remainder of cycles are skipped
Data Collection
Water Meters
1. Zones without Moisture Sensors vs.
2. Zones with Moisture Sensors
Data Collection
Datalogger with a Pressure Switch
How many irrigation cycles were skipped
How much water was saved
Record Soil Moisture