Extra-sensory precipitation

Efficient irrigation doesn’t always mean watering less. It means watering plants according to their needs. Integrating irrigation sensors into a system makes it more responsive, and contractors can more intelligently monitor and manage how the landscape uses water.

“The purpose of a sensor is to give the necessary water that the plant requires, not what the contractor thinks the plant needs,” says Brad Adams, Irrometer factory sales representative. “A sensor acts like a translator, telling the end user whether the area needs to be irrigated or not.”
 

Know your sensors.

Irrigation system sensors monitor four key areas: rain, soil, weather and flow. The most common are rain shut-off sensors. A disk inside collects and absorbs water. When it swells to a certain size, the device trips a switch, shuts down the entire system and prevents further irrigation until the disk dries up.
 

Soil sensors.

These devices work in a similar way to rain sensors – they trip the system when a maximum level of moisture is reached – but are calibrated to the specific needs of plant material and soil types. So, a system with multiple sensors can understand that a light rain is enough for the shrubs, but still allow zones in the lawn to run.

“You are basically teaching (the system) what is the maximum moisture level,” says Burnett Jones, senior marketing manager for Toro. “Once you calibrate, it then has a reference point of where to get back to.”
 

Weather sensors.

Evapotranspiration (or ET) sensors determine when to irrigate by monitoring four weather characteristics: solar radiation, wind speed, temperature and humidity. This information is then used to determine the area’s evapotranspiration rate and then exactly how much should be added back via irrigation.

“ET sensors is where contractors are making the real gains,” says Richard Restuccia, vice president, landscape solutions, Jain Irrigation. “They soon learn that if you apply water properly to the landscape, your landscape thrives, it looks better. I always go back to the analogy of hunger. If I could be fed so I never got too hungry or too full, boy would I be a lot more productive of a person.”
 

Flow sensors.

Primarily used on large, commercial properties, flow sensors can alert the contractor to sudden changes in flow rates and shut down the system if too much water is moving through too fast – preventing erosion, flooding and high water bills.
 

Potential challenges.

One of the risks with sensor responsive water management is that the contractor is largely dependent on the irrigated system functioning effectively.

“If you have a very old irrigation delivery system, undersized, or bad sprinkler heads, then the irrigation will not be very uniform,” Adams says.

“Dry spots show up that much quicker when irrigating based on the sensor. It is easy to point a finger at the controller or the sensor. That’s not the problem. The problem is that the delivery system needs to be either repaired or even replaced.”

Jones agrees, stating that when contractors start to use sensors, they find the areas of weakness in the system that may have been previously masked. It is easy to dismiss this “new finding” on the sensor, but in most cases, the dry areas are directly related to inconsistencies in the irrigation system.

The author is a freelance writer based in Ontario, Canada.