Electric leaf sensors let farmers know when their crops are thirsty

Aug. 30 (UPI) -- New leaf sensors could help farmers keep their crops hydrated without wasting water.

In a new proof-of-concept study, researchers at Penn State University detailed the abilities of their plant-based sensors, which can measure a leaf's thickness and electrical capacitance, revealing whether it is parched or hydrated.

Researchers tested the sensor on tomato plants growing in a controlled environment. They used a soil-moisture sensor to monitor the saturation of the peat potting mixture. As the well-watered peat mixture was allowed to dry out, the researchers observed the changing readings from the leaf sensor.

By measuring the impact of a decreasing water supply on a leaf's thickness and electrical capacitance, researchers were able to develop an algorithm to predict when plants are getting thirsty.

"Leaf thickness is like a balloon -- it swells by hydration and shrinks by water stress, or dehydration," researcher Amin Afzal, a doctoral degree candidate in plant science at Penn State, said in a news release. "The mechanism behind the relationship between leaf electrical capacitance and water status is complex."

"Simply put, the leaf electrical capacitance changes in response to variation in plant water status and ambient light," Afzal said. "So, the analysis of leaf thickness and capacitance variations indicate plant water status -- well-watered versus stressed."

Afzal -- who described the sensor in a paper published this week in the journal Transactions of the ASABE -- believes his sensor could deliver information about a plant's water status to an irrigation system.

A central computer with smart learning software could used the information to decide when and where to deploy water resources, he said. Eventually, all of the information could be delivered wirelessly and sensors could be powered by solar cells.

"I believe these sensors could improve water-use efficiency considerably," said Sjoerd Duiker, an associate professor of soil management at Penn State. "Water scarcity is already a huge geopolitical issue, with agriculture responsible for about 70 percent of world freshwater use. Improvements in water use efficiency will be essential."