Drilling down on water stress sensors

Washington State University researchers share conclusions of two-year study into the use of plant-based sensors to guide irrigation.

Asking a tree its level of stress used to be the provenance of scientists with carefully calibrated equipment. 

But new technology puts such sensors in the hands of growers. Some companies pair traditional research tools, such as dendrometers, with new algorithms and apps to make them more accessible, while others have developed brand new tools.

“It’s critical, as new sensors become available to growers, there needs to be unbiased evaluation of their value to the industry,” said Lee Kalcsits, endowed chair for tree fruit environmental physiology and management at Washington State University. He and postdoctoral researcher Victor Blanco set out to do such an evaluation in apple and pear orchards in 2021 and 2022, with support from the Washington Tree Fruit Research Commission, and they recently shared their results with the industry. 

Kalcsits and Blanco looked at three types of sensors: dendrometers (used on both trunks and growing fruit), sap flow sensors and microtensiometers. All assess plant water status directly.

“If you want to irrigate based on a threshold value, it’s always better to base it on the plant stress, not environmental conditions,” such as evapotranspiration rates or soil moisture levels, Blanco said. “Knowing exactly the water you need is important so you can make decisions based on information.”

Microtensiometers are the newest tool. California-based FloraPulse commercialized the technology developed at Cornell University. The sensors are installed into the trunk at the start of the season and provide real-time updates of trunk water potential, which is a direct measure of the water tension. The sensors offer an alternative to manual pressure bomb tests — the gold standard for assessing plant water stress, Blanco said.

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Taxonomy

• Sensor Systems
• Remote Sensing
• Water Quality Monitoring Sensor