Soil moisture sensors have been incorporated into landscape and irrigation designs for decades. When used correctly, these components offer multiple benefits to an irrigation system. This webinar will go over those benefits and show you how achieve the best possible results. We'll also provide some theory behind designing with soil moisture sensors and pass on a few tricks of the trade learned through dozens of design/build installations.
Note: The following catalog of content covered in this webinar is time stamped to allow you to follow along or skip to sections of the video that are relevant to your questions. You can also search for content on this page using the FIND command in your browser (CTRL + F in Windows, Command + F in Mac OS.)
- Background and History
- Personal Experience
- Theory Behind Designing with Soil Moisture Sensors
- Design Components
- Irrigation Plans with Soil Moisture Sensors
- Soil Moisture Sensors Details
- Flow Management and Programming
- Land F/X Wish List
0:00 – 1:36: Intro/TOC
1:37 – 5:19: Background and History
Wood Architecture background and history (1:37)
Brief history of soil moisture sensors (2:31)
- 7 types of soil moisture sensors (coaxial impedance, dielectric reflectometry, frequency domain reflectometry, time domain reflectometry, time domain tramsmissometry, gypsum blocks, and neutron probes)
- Used heavily in agriculture
- Relatively new in the landscape industry
Soil moisture sensors vs. ET (3:10)
Soil Moisture Sensors
- Provides information in the soil profile at the plants’ root zone.
- Provides data that can be used to adjust irrigation scheduling.
- Incorporates irrigation emitter type, soil type, weather, and mulch into readings.
- Placement is critical.
- Takes time to calibrate.
- Can provide false data.
- Easy to incorporate into irrigation scheduling.
- Can be accessed through on-site or local weather stations.
- Adjusts irrigation based on historic data.
- Applies irrigation schedule adjustments across the board.
- Information based on crop coefficient for turf grass.
- Does not incorporate on-site conditions.
5:20 – 8:42: Personal Experience
Test site: Packwood Creek at Diamond Creek (5:45):
- Low-profile location.
- Hybrid system with conventional and 2-wire.
- 3 soil moisture sensors: one for trees, one for shrubs, and one for existing trees.
- 1-year trial.
- Active management.
- Enabled the system to allow watering seven days a week with sensors.
- Email and text alerts.
- Longest stretch without water was 139 days for trees, 181 for shrubs.
Bridging the application and the academic (7:50)
- Sensor provides moisture levels and temperature levels at the root zone.
- Able to manage separate hydro zones via programs with each sensor.
- Sensor provides actual data that irrigation management and maintenance decisions can be based on.
8:43 – 11:45: Theory Behind Designing with Soil Moisture Sensors
1 sensor for each program type (8:43)
What’s your plant palette? (9:10)
Sun vs. shade (9:20)
Plant sizes (9:45)
Soil types (10:10)
Upper limit vs. lower limit (10:38)
11:46 – 12:09: Design Components
12:10 – 13:13: Irrigation Plans with Soil Moisture Sensors
Plan example: Visalia Vintage Apartments (12:10)
13:14 – 18:02: Soil Moisture Sensors Details
Sensor placement detail (13:14)
Point source irrigation detail (14:20)
Multiple point source irrigation detail (15:50)
Drip spiral detail (16:32)
Inline drip detail (17:25)
18:03 – 20:04: Specifications
“Per manufacturer specification” only means the controller has power and the system is grounded properly.
Other specifications (19:05):
- Controller certification
- Contractor certification
- Moisture sensor maps
20:05 – 22:46: Installation
Trenching and conduits (20:05)
1 1/2-inch conduit is recommended, although 1-inch conduit is also usable.
Wiring the conduits, preventive covering of conduits, prepare to hook up sensor (21:14)
Burying conduit, hooking it into the system, and performing the “bucket test” (21:26)
Ensure that sensor is angled upward (21:50)
Ball valve and sensor hookup (22:14)
22:47 – 24:16: Verification
- Six months of maintenance period minimum.
- Calibrate sensor percentage to plant performance.
- Program sensors to run off moisture.
24:17 – 25:31: Flow Management and Programming
- Per manufacturer specification is not enough.
- High flows, low flows, unexpected flows.
- Moisture percentages.
- Alerts: emails and text messages.
- Plant performance as it relates to sensor data.
25:32 – 29:31: Implementation
- Early meetings with owner/contractors.
- Begin on smaller jobs.
- Don’t overcomplicate sensor placement.
- Know more than the contractor.
- Design irrigation for maintenance programming.
- Keep it simple.
- Minimize pull boxes/locate valves within 50 feet of sensors.
- Sensor to water valve it is connected to.
- Select moisture percentage and verify.
29:32 – 31:37: Examples
Project example 1 (29:32)
Project example 2 (30:55)
31:38 – 33:42: Land F/X Wish List
- Moisture sensor station highlight with stations associated with it.
- Ability to assign valves based n programming category – i.e., trees, shrubs, turf, etc.
- Programming schedule based on sensor location.
- Ability to connect wire from a sensor to valve and generate a wire length.
33:43 – 35:09: Recap
- Design as if you were going to program the controller.
- Keep sensor layout simple.
- The devil is in the details.
- Verification is key.
35:10 – end: Questions
Question: Does the wire absolutely need to be in conduits? (35:45)
Answer: No, it’s not necessary. You can bury the wire directly, which is faster and cheaper. However, it’s easy to cut the wires when they’re bare because they are close to the surface. Conduit provides much more longevity.
Question: How long does it usually take to get an accurate reading on a sensor? (36:55)
Answer: If you can get through a spring and a summer (about 6 months), that would be a good time frame to let you know the plants’ needs.
Question: Do your specs usually include a request that the contractor report back during a certain frequency of visits? How would you monitor reporting on the system? (37:42)
Answer: He tends to use the industry terminology that they want to system to turn on before plants reach their wilting point and turn off before the soil reaches capacity. The designer can then visit the site, observe the conditions, and compare them with historical data to find the “sweet spot” of the system.
Question: Is there a certain frequency at which the designer should visit the site to check the sensors? (39:40)
Answer: Not really. Just verify that the system is installed correctly, and check the reports, which will provide a good indication of whether it’s working correctly.
Question: Why does the sensor have to point upward? (41:41)
Answer: That’s the way it’s set up. The wires are meant to run perpendicular to the sensor.
Question: Would you ever, or can you even, add multiple sensors to a valve or location? (42:17)
Answer: Yes you can – it depends on your intent for the system.
Question: What is the ideal number of sensors for a site? (43:50)
Answer: It will depend on the variables of the site. A flat site with three different plant types will require three. A more complex site may require five or six. A sloped site may require some at the top of the slope and some at the bottom.