Ultrasonic plant acoustic monitoring for precision agriculture

Overview

This research explores the emerging field of plant bioacoustics, investigating whether plants emit detectable airborne ultrasonic sounds when under stress. Prior studies have recorded vibrations from plants only through direct contact with sensors, leaving open the question of whether these vibrations propagate through the air at meaningful distances. The project aims to construct a reliable recording system capable of capturing airborne ultrasonic emissions from plants, potentially opening new avenues for precision agriculture where crop water status can be monitored remotely by sound.

The value proposition centers on enabling early, non-invasive detection of drought stress in crops. If plants reliably emit ultrasonic signals when water-starved, farmers and agronomists could deploy acoustic sensors across fields or greenhouses to monitor plant health in real time, optimizing irrigation schedules and reducing water waste. Beyond agriculture, the research may reveal new dimensions of plant-environment communication, with potential implications for ecological monitoring and crop pest management.

Technical specifications

Research approach:

• Construction of an acoustic isolation box for controlled recording of plant sounds
• Simultaneous dual-microphone recording to verify signal consistency and rule out artifacts
• Focus on the ultrasonic frequency range of 20–150 kHz, where ambient background noise is minimal
• Test species include tomato (Solanum lycopersicum) and tobacco (Nicotiana tabacum)
• Stress treatments include drought stress, mechanical cutting of stems, and unstressed controls

Preliminary findings informing the work:

• Tomato plants under drought stress have been observed to produce ultrasonic emissions at frequencies up to 100 kHz
• Microphones placed 10 cm from plants successfully captured these signals
• The frequency range overlaps with insect hearing capability, suggesting ecological relevance
• Initial estimates indicate insects could detect plant sounds from distances up to 5 meters

Planned validation:

• Laboratory validation within the acoustic box environment
• Greenhouse testing under semi-natural conditions to assess real-world signal propagation

Technology readiness level

This research is at an early exploratory stage, corresponding to Technology Readiness Level 2–3 (concept formulation and laboratory validation). Prior published observations from other groups have demonstrated that drought-stressed plants can produce detectable ultrasonic emissions, but the extent of airborne propagation, repeatability across species, and practical signal range remain open questions. The current project focuses on building and validating the foundational recording methodology before scaling to field conditions. Further development will be needed to translate laboratory findings into deployable sensor systems suitable for commercial agricultural use.