@jsbrava, thanks for sharing this list! I’ve heard of them all and have my favorites. The biggest issue I’ve seen over the years with soil sensors is proper installation, and accurate reporting of ONE sensor to manage an entire landscape. A single sensor can be used to control the irrigation for many zones (where an irrigation zone is defined by a solenoid valve) or multiple sensors can be used to irrigate individual zones. In the case of one sensor for several zones, the zone that is normally the driest, or most in need of irrigation, is selected for placement of the sensor in order to ensure adequate irrigation in all zones. Many lawns have multiple micro-climates that they need to account for; from south-facing and full sun to north-facing with a slope, a mesh network of sensors is the best approach for a true closed loop feedback of your lawn’s health.
It’s important to remember that by design, smart irrigation controllers vary based on the type of data they are using. There are generally two types of smart controllers: climatologically-based (ET) controllers and soil moisture-based (SMS) controllers.
- Climatologically based controllers are also known as evapotranspiration, or ET controllers. Generally, ET is the process of transpiration by plants combined with evaporation that occurs from plant and soil surfaces.
- Soil moisture sensor controllers, or SMS controllers, can be divided into two types; “bypass” and “on-demand”:
BYPASS: The bypass configuration is the most common for residential sites. Typically, a bypass SMS controller has a soil moisture threshold adjustment from “dry” to “wet”. This threshold can be used to lower and raise the point at which the irrigation system is allowed to water to suit specific plant, soil, and microclimate needs. This type of controller bypasses timed irrigation events if the current soil moisture content exceeds the adjustable threshold. The bypass mode of operation is very similar to that of a rain sensor
ON-DEMAND: An on-demand SMS controller initiates irrigation at a pre-programmed low soil moisture threshold and terminates irrigation at a high threshold. This type of controller is often used where a high level of customization or high level of control is needed such as commercial sites or other types of sites with many irrigation zones. Thus, this controller initiates and terminates irrigation events, whereas the bypass controller only allows irrigation events (i.e. day of the week, time of day, and run time) from a time clock. Therefore, it is critical to properly program a schedule into the time clock.
The Iro can be setup with a wired soil moisture sensor to achieve bypass scheduling.
Please keep in mind some general rules for the burial of the soil moisture sensors, which include:
- Soil in the area of burial should be representative of the entire irrigated area.
- Sensors should be buried in the root zone of the plants to be irrigated, because this is where plants will extract water. Burial in the root zone will help ensure adequate turf or landscape quality. For turfgrass, the sensor should typically be buried at about three inches deep.
- Sensors need to be in good contact with the soil after burial; there should be no air gaps surrounding the sensor. Soil should be packed firmly but not excessively around the sensor.
- If one sensor is used to control the entire irrigation system, it should be buried in the zone that requires water first, to ensure that all zones get adequate irrigation. Typically, this will be an area with full sun or the area with the most sun exposure.
- Sensors should be placed at least 5 feet from the home, property line, or an impervious surface (such as a driveway) and 3 feet from a planted bed area.
- Sensors should also be located at least 5 feet from irrigation heads and toward the center of an irrigation zone.
- Sensors should not be buried in high traffic areas to prevent excess compaction of the soil around the sensor.
Hopes this helps anyone interested in soil sensors 
Best, Emil
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