Beneath-Leaf Sensors May Offer Real-Time Insights Into Crop Health

Monitoring crop health from aerial images has its limits, as they can only provide a broad overview. Enter a groundbreaking spectral sensor designed to attach directly to the underside of individual plant leaves.

However, developed by Ko-ichiro Miyamoto, Kaori Kohzuma, and their team at Japan’s Tohoku University, this device is meant to be placed on several “sentinel plants” scattered across a field. The sensor is composed of two main components.

The setup includes a sensor head attached to the underside of a leaf, ensuring it doesn’t block sunlight. This head connects via a cable to a nearby control unit, which houses a lithium battery, an Arduino microprocessor, an antenna, and other electronic components.

Leaf Illumination and Light Measurement

At set intervals, the sensor head uses two LEDs to briefly illuminate the leaf’s underside. A photodiode between the LEDs analyzes the spectrum of the reflected light. Additionally, the diode measures sunlight passing through the leaf when the LEDs are off.

In fact, by subtracting the sunlight measurement from the LED reading, the system determines the spectrum of light absorbed by the leaf. This data reveals the leaf’s current color, a key indicator of plant health and seasonal changes.

The collected sensor data is processed on a cloud server, accessed through a cellular network, and made available to users.

Sensor Deployment and Data Collection on Golden Birch Leaves

During testing, several sensor units were affixed to the leaves of golden birch trees in the University of Tokyo’s experimental garden. Over two weeks, the sensors automatically collected data every two hours as the leaves naturally changed color from green to yellow or brown.

When analyzed, the sensor data closely matched results from handheld spectrometers used by researchers during the same period. However, in large-scale agricultural settings, relying on handheld devices would be far more labor- and time-intensive compared to using the automated sensors.

The prototype sensors cost “a few tens of dollars” each to fabricate, though mass production could significantly lower the price.

To conclude, “This cost-effective sensor offers a practical solution for monitoring plant health and stress by analyzing leaf color and light reflection,” says Kohzuma. “Its affordability allows for deploying multiple sensors across different locations, enabling a network for comprehensive, real-time monitoring.”

Read the original article on: New Atlas

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