Soil Health Monitoring

Summary

As agriculture faces intensifying pressures from climate instability to soil degradation the need for real-time, biologically meaningful soil diagnostics has never been greater. Yet most commercial sensors remain limited to physical and chemical metrics, overlooking the microbial and fungal dynamics that truly define soil vitality. Fungal mycelium, in particular, offers a rich biological signal: its metabolic activity reflects nutrient cycling, pollutant stress, and biodiversity shifts. By harnessing live fungi as biosensors, we can move beyond lab-bound testing toward in situ, intelligent sensing systems that reveal the living complexity of soil ecosystems.

Introduction

In the face of mounting agricultural challenges—including climate variability, soil degradation, and the urgent need for sustainable practices—accurate and timely soil health assessment has become more critical than ever. However, the tools currently available on the market fall short of capturing the full biological complexity of soil ecosystems.

Modern soil sensors use a range of technologies to measure key physical and chemical parameters. Common models assess volumetric moisture content through dielectric properties, soil tension via electrical resistance, and nutrient concentrations using electrochemical or optical methods. Some specialise in monitoring soil temperature with thermistors, electrical conductivity to evaluate salinity and fertility, and pH through ion-selective electrodes. Advanced multi-parameter sensors combine these functions into a single unit, offering comprehensive soil diagnostics. Despite their utility, these tools have several limitations. They lack biological resolution and cannot detect microbial activity, fungal dynamics, or organic matter decomposition. Most rely on point-based measurements, which may misrepresent broader soil conditions due to spatial variability. Biological indicators such as microbial diversity or fungal presence still require laboratory testing, including DNA sequencing, culturing, or respiration analysis, making the process time-consuming and resource-intensive.

Fungi play a foundational role in soil health. They drive nutrient cycling and organic matter decomposition, form symbiotic relationships with plants (such as mycorrhizae), and respond sensitively to pollutants, compaction, and biodiversity shifts. Fungal mycelium, in particular, serves as a powerful bioindicator due to its direct involvement in key soil processes. It contributes to nutrient cycling by breaking down organic matter and releasing essential elements like nitrogen and phosphorus. Its hyphal networks help form soil structure by binding particles and improving porosity and aeration. Mycorrhizal fungi enhance water and nutrient uptake in plants, while some fungal species suppress disease by outcompeting pathogens or producing anti-fungal compounds. Additionally, fungal biomass plays a role in long-term carbon sequestration.

When soil conditions deteriorate due to pollution, drought, or nutrient imbalance, mycelial activity declines. These changes can be detected through shifts in electrical signalling. A biosensor system based on live fungal species offers a biologically intelligent alternative to conventional sensors. By observing fungal metabolic responses to soil, such a system can infer soil vitality and nutrient richness, detect pollutants or heavy metals, assess microbial diversity and nutrient cycling efficiency, and reveal changes in soil structure and biodiversity. This approach removes the need for complex laboratory protocols and enables real-time, in situ biological sensing, offering a more holistic understanding of soil health.

There is no known patent that directly covers a fungal-based soil health sensor system that uses mycelial bioelectric signalling as the primary sensing mechanism. That said, there are related technologies in the broader space of soil sensing and microbial interfaces (please see references section).

Advantages of a Fungal Biosensor System:

  • Biological Activity Monitoring: Conventional sensors are unable to measure microbial or fungal dynamics, limiting their capacity to assess biological processes. In contrast, a fungal biosensor could actively track phenomena such as mycelial growth and metabolism, offering a direct window into living systems.
  • Pollutant Detection: While conventional sensors rely on indirect chemical indicators to infer pollution levels, a fungal biosensor could detect pollutants through biological responses. These include stress signalling and metabolic shifts, providing a more nuanced and responsive detection method.
  • Soil Biodiversity Sensitivity: Conventional sensors lack sensitivity to microbial diversity and ecological changes, making them ineffective for biodiversity monitoring. Fungal biosensors, however, could respond to shifts in biodiversity, delivering ecological insights that conventional tools overlook.
  • Laboratory Dependence: Many conventional sensors require laboratory testing—such as DNA sequencing—to obtain biological data. Fungal biosensors would bypass this need by enabling direct, in situ biological sensing, eliminating the dependency on lab protocols.
  • Real-Time, In Situ Sensing: Conventional sensors are typically limited to measuring physical and chemical parameters, which may not reflect biological health. Fungal biosensors would provide immediate feedback on soil conditions through live fungal responses, enabling real-time ecological assessment.
  • Affordability for Smallholders: The cost and complexity of conventional sensors often make them inaccessible to small-scale farmers. Fungal biosensors can be constructed as modular, low-tech, and designed for affordability, making them suitable for deployment in diverse agricultural and environmental settings.

Soil Health Metrics Detectable via Mycelial Sensors:

  • Moisture: Fungal biosensors will respond to moisture through changes in hyphal conductivity and ion transport. These physiological shifts manifest as electrical signal variations, including voltage spikes or drops and impedance fluctuations, offering a dynamic readout of hydration levels.
  • pH: Variations in pH influence fungal membrane potential and enzyme activity. These biochemical responses translate into altered electrical signals, typically seen as changes in spike frequency or amplitude within the biosensor’s output.
  • Nutrient Levels: Fungal growth rate and metabolic activity are sensitive indicators of nutrient availability. As these biological processes intensify or diminish, the biosensor can reflects the change through increased signal complexity and frequency modulation.
  • Heavy Metals / Toxins: Exposure to heavy metals or toxins suppresses fungal enzyme function and triggers stress signalling pathways. These disruptions lead to dampened electrical signals and reduced spike activity, serving as a biological alert system for contamination.
  • Microbial Diversity: Fungal biosensors would engage in symbiotic and competitive interactions with surrounding microbes. These ecological dynamics produce distinct signal patterns and heightened noise complexity, revealing shifts in microbial diversity.
  • Temperature: Temperature fluctuations affect fungal metabolic rates and ion channel behaviour. These physiological changes result in amplitude shifts and delayed signal responses, enabling the biosensor to track thermal conditions in real time.

What Fungal Bioelectric Signals Look Like:

  • Fungal Electrical Signalling: Fungal mycelium produces low-voltage electrical pulses in response to environmental stimuli. These signals often take the form of voltage spikes or bursts, resembling action potentials observed in neurons. Additionally, the amplitude of these signals may oscillate over time, reflecting underlying metabolic rhythms. Impedance shifts are also common, typically resulting from ion transport and variations in moisture content.
  • Voltage Amplitude: Signal strength typically ranges from approximately 100 microvolts to 10 millivolts. This amplitude varies depending on the fungal species involved and the specific soil conditions in which the biosensor operates.
  • Frequency: Signal frequency spans from about 0.1 Hz to 10 Hz. This includes both slow oscillatory patterns and rapid bursts, offering a dynamic profile of fungal activity.
  • Duration: Individual spikes generally last between 1 and 10 seconds. These durations tend to be irregular and are closely tied to the nature and intensity of environmental stimuli.
  • Impedance: Electrical impedance within fungal biosensors ranges from roughly 10 kilo-ohms to 1 mega-ohm. These values are influenced by factors such as moisture levels and the concentration of ions in the surrounding medium.

Based on studies and reviews (please see the references section), three simulated scenarios are outlined below:

Selected Fungal species for incorporation into a biosensor

a) Ganoderma lucidum – Soil vitality and nutrient richness

Ganoderma lucidum, also known as “Reishi” or “Lingzhi,” is a wood-decaying basidiomycete with a long history in traditional medicine and ecological research. In soil ecosystems, it helps decompose lignin and complex organic matter, contributing to nutrient cycling and humus formation. Its growth responds sensitively to soil pH, organic carbon levels, and enzymatic activity, especially phosphatases and oxidases, making it a reliable long-term indicator of soil vitality.

Studies have shown that G. lucidum’s metabolite profile shifts in response to soil conditions, including the availability of nitrogen and phosphorus. These metabolites, such as ganoderic acids and polysaccharides, can be detected optically or electrochemically, offering a stable biosensing platform. Because it thrives in well-balanced, biologically active soils, its presence and metabolic output can reflect the overall health and sustainability of the soil environment.

Ganoderma lucidum produces slow, rhythmic voltage oscillations with amplitudes typically ranging from 2 to 5 millivolts and frequencies around 0.5 to 1 Hz. Its electrical behavior is stable and consistent, responding to changes in moisture and nutrient availability with gradual signal shifts. This species is particularly well-suited for long-term soil monitoring, offering a reliable reflection of overall soil vitality.

b) Trametes versicolour – Presence of pollutants or heavy metals

Trametes versicolour, commonly called “Turkey Tail,” is a white-rot fungus renowned for its potent enzymatic arsenal, particularly laccases and manganese peroxidases. These enzymes allow it to break down complex pollutants like industrial dyes, polycyclic aromatic hydrocarbons (PAHs), and heavy metals. Its biochemical response to contaminants is rapid and measurable, making it an ideal candidate for biosensing soil toxicity.

In polluted soils, T. versicolour exhibits altered growth patterns, increased enzyme secretion, and shifts in metabolite production. These changes can be monitored using colorimetric or electrochemical sensors, providing real-time feedback on soil contamination levels. Its ability to detoxify cadmium, copper, and lead has been well documented, and its resilience in harsh environments makes it a robust biological sensor for environmental monitoring.

Trametes versicolour emits high-frequency, low-amplitude pulses, typically between 0.5 and 1.5 millivolts, with frequencies in the 3 to 5 Hz range. It is highly sensitive to environmental pollutants and heavy metals, with signal dampening observed in contaminated soils. This species excels in environmental monitoring applications, particularly for detecting soil contamination.

c) Pleurotus ostreatus – Indicator of Microbial Diversity and Nutrient Cycling

Pleurotus ostreatus, known as the “Oyster Mushroom,” is a saprophytic fungus that grows on decaying organic matter and interacts actively with soil microbial communities. It secretes a variety of enzymes, including cellulases, proteases, and kininases, which break down plant residues and improve nutrient availability. Its growth and metabolic activity reflect microbial diversity and overall soil fertility.

Research has shown that P. ostreatus can improve soil microbial structure, increase populations of beneficial fungi like Trichoderma and Penicillium, and boost nitrogen and phosphorus cycling. These traits make it a powerful biosensor for assessing soil biological richness and nutrient dynamics. Its VOCs and secondary metabolites can also serve as indicators of microbial competition and organic matter decomposition, providing a multi-layered view of soil health.

Pleurotus ostreatus generates moderate-frequency bursts interspersed with occasional voltage spikes. Signal amplitudes fall between 1 and 3 millivolts, with frequencies ranging from 1 to 3 Hz. It is highly responsive to pH fluctuations and microbial competition, showing increased activity in compost-rich environments. This makes it an effective biosensor for tracking microbial diversity and nutrient cycling.

d) Mycena spp. – Sensor of Soil Compaction and Biodiversity Shifts

Mycena species are small, delicate fungi commonly found in undisturbed forest soils and biodiverse ecosystems. They respond sensitively to changes in soil structure, moisture, and oxygen availability, which are influenced by soil compaction and degradation. Their presence often indicates a healthy, aerated, and biologically rich soil environment.

Ecological studies suggest that Mycena spp. can form root associations and respond to shifts in microbial and plant diversity. In compacted or low-biodiversity soils, their growth is inhibited, and sporulation declines. These traits make them excellent indicators of physical soil health and ecological balance. By monitoring their biomass, metabolic activity, or even DNA presence, a sensor system can detect subtle changes in soil structure and biodiversity that conventional sensors often miss.

Mycena species display irregular, erratic electrical spikes with amplitudes ranging from 0.1 to 0.5 millivolts and variable frequencies often below 1 Hz. Their signal behavior is unstable in dry or compacted soils but becomes more complex in biodiverse environments. These characteristics make Mycena spp. valuable for mapping soil stress and assessing microbial richness.

Design Strategy: Shelf-Stable, Ready-to-Use Mycelial Sensor Layer

To ensure practical deployment and long-term usability, the mycelial sensor layer must meet several key requirements. It should have a shelf life of at least 6 to 12 months, require no reconstitution or cultivation, and maintain bioelectric responsiveness during storage. The material must be non-toxic and compatible with embedded electrodes to allow seamless integration into sensing systems.

The ideal format for this sensor layer is a dehydrated, pre-grown mycelial composite. Typically cultivated from species such as Ganoderma lucidum or Pleurotus ostreatus, the mycelium is grown on a porous substrate like straw or biochar under controlled factory conditions until full colonisation is achieved. It is then dehydrated to a moisture content of approximately 10–15%, which halts metabolic activity while preserving the integrity of the hyphal network. Upon contact with soil moisture, the matrix passively reactivates. This rehydration process restores metabolic and electrical responsiveness without requiring full regrowth, enabling immediate sensing functionality in the field.

When sealed with a desiccant, the dehydrated mycelial composite maintains its functionality for 6 to 12 months. Shelf life can be extended further through vacuum sealing or storage in cool, dry environments. Studies on dispersion analysis of living, dehydrated, and rehydrated mycelium confirm that electrical signal transmission remains intact after dehydration, provided humidity is restored. Additionally, mycelium-based biomaterials used in packaging and construction have demonstrated long-term structural and functional stability when properly dried and stored.

For consumer-ready deployment, the sensor could be packaged as a flat disc or plug about 2–3 cm in diameter, embedded with electrodes. Each unit would be vacuum-sealed in a moisture-barrier pouch and include a QR code with setup instructions. Activation is simple: insert the sensor into a slurried soil mixture. A small moisture indicator strip could be included to confirm successful activation.

This design must offer plug-and-play usability, eliminating the need for specialised handling or lab protocols. It must pose no contamination risk from spores or live cultures and preserves the biological intelligence of the fungal network. The format must be compatible with electronic systems and scalable for mass production, making it an accessible and practical solution for both researchers and smallholder farmers.

Sensor Design

The proposed system is composed of four interchangeable probe heads, each tailored to a specific fungal species and soil health parameter. These heads connect to a central body that manages signal acquisition, processing, and display. The design is scalable, user-friendly, and adaptable to different soil types and conditions.

The following section a) to c) below serve as a conceptual mock-up of the biosensor design.

a) Probe Head Assembly: Modular Fungal Biosensing Unit

The biosensor system comprises four interchangeable probe heads, each engineered to house a distinct fungal species selected for its ecological sensitivity to specific soil health parameters. These heads are designed as sealed, compact modules that can be inserted directly into soil slurry samples or field soil for real-time biological sensing.

Form Factor and Dimensions:

  • Shape: Slim disc or puck
  • Diameter: ~2.5–3.0 cm
  • Thickness: ~1.5–2.0 cm
  • Weight: <50 g per module
  • Mounting: Snap-fit or magnetic docking into handheld base

Biological Core: Fungal Matrix Substrate

At the core of each probe lies a fungal matrix cultivated on a tailored substrate designed to support species-specific growth and metabolic activity. This matrix is dehydrated during storage, enabling a long shelf life and rapid deployment. Upon contact with moisture, it reactivates naturally, resuming its biological functions without the need for cultivation.

Substrate materials are selected based on the fungal species. Ganoderma lucidum thrives on hardwood chips and biochar, while Trametes versicolour prefers straw and lignin-rich fibres. Pleurotus ostreatus grows well on corn husks and cellulose-rich straw, and Mycena species are suited to leaf litter and fine wood dust.

The matrix itself is configured as a porous, layered structure to maximise surface area. It is embedded within a breathable chamber that allows for gas exchange and is pre-inoculated with fungal mycelium, stabilized using natural binders to maintain integrity during storage and activation.

This biological core functions as a living sensor, dynamically responding to soil conditions through shifts in enzyme activity, metabolite production, volatile organic compound (VOC) emission, and biomass growth. Its responsiveness enables real-time insight into soil health and environmental changes.

Electrochemical Interface: Embedded Electrode Array

The biosensor system would use a flexible carbon-coated copper mesh, sealed with a thin biopolymer layer to prevent leaching and maintain electrical conductivity. This mesh is embedded directly into the fungal substrate during active mycelial cultivation or after drying, ensuring close contact with the living fungal tissue. By placing the mesh within the mycelial layer, the system captures electrical signals from fungal metabolic processes with minimal disruption to growth or structure.

Electrode contact points are distributed across the mesh in a radial or grid configuration, typically using 3 to 5 nodes to optimise spatial coverage and signal resolution. The carbon coating enhances biocompatibility and signal fidelity, allowing for stable and sustained interaction with the fungal network over time.

The embedded mesh connects to a miniature signal conditioning circuit that amplifies and filters raw bioelectric signals for accurate interpretation. This setup enables the detection of several key parameters: impedance shifts linked to biomass expansion, redox activity associated with enzyme secretion (such as lactase and phosphatase), and conductivity changes triggered by pollutants or nutrient fluctuations.

Together, this integrated interface supports non-invasive, real-time monitoring of fungal responses. It translates subtle biological activity into quantifiable electrical signals, offering a dynamic and ecologically grounded view of soil health and environmental conditions.

Signal Conditioning and Feedback System

Each probe head contains a miniature signal conditioning circuit that pre-processes raw electrical data before transmitting it to the central microcontroller. This circuit plays a crucial role in ensuring signal clarity and reliability by amplifying low-voltage bioelectric signals, filtering out noise, and correcting baseline drift. In some configurations, it also performs analog-to-digital conversion, enabling standalone diagnostics without external processing hardware.

To provide immediate, user-friendly feedback, the probe includes an integrated LED indicator system. A green light signals optimal fungal response, reflecting healthy soil conditions. An orange light indicates moderate stress or imbalance, such as low moisture or nutrient deficiency. A red light warns of degraded, contaminated, or biologically inactive soil. During calibration, a blue light appears to confirm active baseline recording.

This visual feedback mechanism allows users to interpret soil health status instantly, even without a connected display or mobile app, making the system intuitive and accessible for field use.

Connectivity: Modular Attachment System

Each probe head features a magnetic or snap-fit connector that enables secure and intuitive attachment to the central body. These connectors may include magnetic pogo pins or waterproof snap-lock terminals, providing both durability and ease of use in outdoor conditions. A shielded cable interface ensures reliable transmission of signal and power between the probe head and the central system. To simplify deployment and identification, each connector is colour-coded or labelled according to fungal species, using a system such as A through D.

The design supports plug-and-play functionality, allowing probe heads to be swapped out seasonally or adapted to different soil types without the need for tools. This makes replacement quick and accessible in the field. The central microcontroller automatically recognises each probe head through embedded identifiers or resistance signatures, streamlining setup and calibration.

This modular approach offers flexibility, scalability, and ease of maintenance, making the system highly practical for both field researchers and smallholder farmers seeking reliable, biologically intelligent soil monitoring.

Housing and Environmental Protection

The outer casing of each probe head is built from materials that are both durable and functional, offering waterproof protection while remaining breathable to support fungal respiration. The structural shell incorporates sustainable biopolymers such as PLA or PHA, chosen for their environmental compatibility. For added resilience and flexibility, components like silicone or TPU can be used to absorb impact and withstand field conditions. To facilitate gas exchange, microporous membrane vents are integrated into the casing, allowing airflow without compromising internal integrity.

Beyond basic protection, the casing includes several environmental features to ensure long-term viability. A UV-resistant coating shields the probe from sun exposure during outdoor use, while an anti-fungal mesh prevents contamination from external spores. Thermal insulation helps stabilise the internal microclimate, preserving the delicate balance required for fungal responsiveness.

Together, these design elements create a robust housing that maintains the health and functionality of the fungal matrix, even in variable and challenging field environments.

b) Central Body (Probe Handle): Compact Control Hub

The central body is a handheld, ergonomic unit designed to dock with the four miniaturised fungal probe heads. It serves as the system’s processing core, managing electrical signals, calibration routines, power distribution, and user interaction. The design prioritises portability, modularity, and intuitive operation for field use.

Physical Design and Layout

  • Dimensions: Approx. 10–12 cm wide × 5–6 cm tall × 2–3 cm thick
  • Weight: ~200–300 g (including battery)
  • Form: Curved or contoured casing for comfortable grip
  • Material: Durable ABS or biopolymer shell with rubberised edges for shock resistance
  • Ports: Four recessed docking slots for probe heads (magnetic or snap-fit)

The compact footprint allows the entire system to be held in one hand, with probe heads arranged in a radial or linear layout for easy access and visual feedback.

Core Electronics and Signal Management

At the heart of the system is a microcontroller unit (MCU), typically an ESP32 or similar low-power, high-performance chip. This MCU reads analog signals from each probe head, controls LED indicators and the optional display, manages calibration routines, and handles wireless communication. It also stores reference profiles and test results for ongoing diagnostics.

To support multiple probes simultaneously, a multiplexer switches sequentially between probe head inputs. This setup reduces the number of required MCU pins and keeps all probes connected. Analog fungal responses, including impedance and redox current, are converted into digital data using a high-resolution analog-to-digital converter, typically 12 to 16 bits, to ensure signal fidelity and precision.

Power System

The device is powered by a rechargeable lithium-ion battery, generally rated between 1000 and 1500 mAh. Charging is handled via a USB-C port, with optional solar panel integration for off-grid use. Power management features include a low-power sleep mode when idle, automatic shutoff after periods of inactivity, and a battery level indicator displayed either on the screen or via an LED strip.

Connectivity and Expansion

Wireless connectivity is available through optional BLE or Wi-Fi modules, enabling seamless syncing with a mobile app or cloud dashboard. Internal memory stores recent test results and calibration profiles, supporting offline use. Firmware upgrades can be delivered over-the-air (OTA) via the app or through a USB connection, ensuring the system remains up-to-date.

User Interface and Feedback

Visual feedback is provided through either a colour-coded LED strip or an OLED display. The LED strip summarises soil health across all four probes: green indicates healthy conditions, orange signals moderate stress, and red denotes degraded soil. The OLED display, if included, shows detailed information such as fungal species, signal strength, calibration status, and timestamps.

A dedicated calibration button initiates the calibration sequence using reference soil cartridges. During calibration, LEDs flash blue and turn off once complete. To prevent accidental activation, the button requires a long press.

Probe Docking System

The probe docking system uses magnetic pogo pins or waterproof snap-fit terminals for secure and intuitive connections. Auto-alignment guides ensure quick insertion, and each slot is colour-coded or labelled (A–D) to match fungal species. Each probe contains a unique ID resistor or EEPROM chip, allowing the MCU to auto-identify the probe type and load the appropriate calibration profile.

Environmental Durability

Designed for field use, the central body features an IP65-rated casing that resists dust and splashes. It operates reliably within a temperature range of 0–40°C, suitable for most agricultural and ecological environments. Internal padding and rubberised edges provide shock absorption, protecting the electronics during transport and handling.

c) Calibration Station: Baseline Signal Profiling Hub

The Calibration Station is a compact, bench-top unit designed to standardise the electrical and biological responses of each fungal probe head. It enables users to establish reference profiles using controlled soil conditions, ensuring that subsequent readings in the field are accurate and meaningful.

Reference Soil Cartridge Set

Each fungal species used in the biosensor system requires a tailored soil environment to properly calibrate its metabolic and electrical response. To support this, the system includes four reference soil cartridges, which can be purchased separately or bundled with the device. Each cartridge is matched to a specific fungal species: Cartridge A is formulated for Ganoderma lucidum, Cartridge B for Trametes versicolour, Cartridge C for Pleurotus ostreatus, and Cartridge D for Mycena spp.

These cartridges are packaged in airtight containers to preserve their integrity during storage and transport. Each unit includes a desiccant pack to maintain low humidity and prevent premature activation. The cartridges are clearly labelled A through D, with the corresponding fungal species and calibration instructions printed on each container for easy identification. Under dry conditions, the reference cartridges remain shelf-stable for approximately 6 to 12 months, ensuring reliable calibration performance over time.

Calibration Tray

The Calibration Tray is a reusable platform designed with four compartments, each precisely sized to hold one probe head securely. Its purpose is to facilitate controlled immersion and reliable signal acquisition during the calibration process. Constructed from non-reactive polymers such as HDPE or silicone, the tray ensures chemical stability and durability in field conditions. Each compartment is approximately 2 centimetres deep, allowing full contact between the probe and the soil slurry. For easy clean-up, the tray may include a removable base or an absorbent pad to manage excess moisture.

To perform calibration, insert reference soil into each compartment. Add 5 to 10 millilitres of distilled water to create a slurry, then mix gently to ensure consistency. Insert the corresponding probe head, labelled A through D, into each compartment. Wait about five minutes for the fungal matrix to reactivate and for the electrical signals to stabilise. This ensures accurate baseline readings for subsequent diagnostics.

Calibration Process and Signal Capture

Once the probe heads are immersed in the soil slurry, the central microcontroller automatically begins the calibration sequence. It starts by acquiring electrical signals from each fungal matrix, reading parameters such as impedance, redox current, and conductivity. These signals are filtered to remove noise and normalised across all probe heads to ensure consistency.

The system stores a baseline signal profile for each fungal species and links it to a specific soil type or environmental tag, such as “Loamy – Spring.” During calibration, the LED on each probe flashes blue to indicate active processing. When calibration is complete, the LED turns off. If the device includes an OLED display, it shows a confirmation message like “Calibration Successful” or displays error codes if any issues are detected.

Users have the option to repeat calibration with different soil types to build a library of reference profiles. This enhances the system’s adaptability across regions and seasons, allowing for more precise diagnostics.

Calibration is essential because fungal responses can vary depending on moisture levels, temperature, and the age of the substrate. Electrochemical sensors may also experience baseline drift over time or between batches. By calibrating to local soil conditions, users improve diagnostic accuracy and reduce the likelihood of false positives.

Testing Chamber: Soil Health Diagnostic Interface

The Testing Chamber serves as the operational heart of your biosensor workflow, where real-world soil samples are analysed through direct interaction with the fungal probe heads. Designed for both field and lab use, this compact unit enables rapid, biologically informed diagnostics by immersing each probe into a prepared soil slurry. The chamber is engineered to standardise the testing process, ensuring consistent probe-soil contact and reliable signal acquisition.

To begin, soil samples should be collected from representative zones within the target area. Ideally, samples are taken from the topsoil layer (0–10 cm), where microbial activity and organic matter are most concentrated. For more comprehensive analysis, users may also collect subsurface samples (10–20 cm) to assess compaction, nutrient leaching, or pollutant accumulation. Each sample should be placed into a clean container and labelled according to depth or location.

Once collected, the soil is transferred into the Testing Tray, which includes four dedicated compartments matched to specific fungal probe heads. The tray is made from a non-reactive polymer such as HDPE or silicone to ensure chemical neutrality and easy cleaning. Each compartment is sized for full immersion of the probe head, with a depth of about 2 cm and a volume capacity of roughly 20 ml. To activate the fungal matrix, users add 5 to 10 ml of distilled water to each compartment, forming a slurry that mimics natural moisture conditions like dew or light rainfall. This slurry stimulates microbial and fungal metabolic activity, allowing the biosensor to detect biologically relevant changes.

After preparing the slurry, insert the probe heads into their designated compartments. The central unit begins signal acquisition automatically, activating each probe in sequence through its internal multiplexer. Electrical signals, including impedance shifts, redox currents, and conductivity changes, are captured and processed by the microcontroller. These signals are compared to the calibration baselines stored in memory, enabling the system to interpret soil health status in real time.

Each probe head is equipped with an LED indicator that provides immediate visual feedback, as follows:

  • Green light signifies optimal fungal response, indicating healthy and biologically active soil
  • Orange light suggests moderate stress or imbalance
  • Red light signals degraded, compacted, or contaminated conditions.

This intuitive colour-coded system allows users to assess soil health at a glance, without requiring external devices or data analysis.

For users with the OLED-equipped version of the central unit, a summary display shows the fungal species, signal strength, and timestamp for each test. If wireless connectivity is enabled, results can be synced to a mobile app or cloud dashboard for long-term tracking and spatial mapping. This integration supports data-driven decision-making in agriculture, ecology, and land management.

The Testing Chamber is designed to be reusable and easy to maintain. After each use, the tray and probe tips should be rinsed with distilled water to prevent cross-contamination. The compact form factor and standardised workflow make it ideal for rapid deployment in the field, empowering users to monitor soil health with precision and biological insight.

Firmware Logic and Signal Interpretation

This section serves as a conceptual outline of the logic and signal interpretation of the biosensor.

Probe Initialisation and Identification: When the device powers on or a probe head is inserted, the firmware begins by scanning each docking port to detect the presence of a connected probe. This is achieved either through electrical signature recognition or by reading a unique EEPROM ID embedded in each probe. Once identified, the microcontroller loads the corresponding fungal species profile and calibration data from memory. This ensures that each probe is matched with the correct signal interpretation parameters. A brief LED flash confirms successful recognition, allowing the user to verify that all probes are properly seated and ready for operation.

Signal Acquisition and Conditioning: The system then enters the signal acquisition phase. Using a multiplexer, the microcontroller sequentially activates each probe head and reads the analog signals generated by the fungal matrix via the embedded electrode array. These signals may include impedance changes due to biomass growth, redox currents linked to enzyme activity, and conductivity shifts that reflect pollutant presence or nutrient levels. Raw signals are passed through a low-pass filter to remove noise and then normalised against stored calibration baselines. This ensures consistent and accurate readings across different environmental conditions and probe batches.

Calibration Routine: Calibration is initiated by a long press of the dedicated calibration button. During this process, each probe head is immersed in its corresponding reference soil slurry, allowing the fungal matrix to reactivate and stabilize. The microcontroller records the electrical signal profile generated under these controlled conditions and stores it as a baseline in non-volatile memory. This baseline serves as a reference point for future comparisons during field testing. During calibration, the LED on each probe flashes blue to indicate active profiling and turns off once the process is complete. This routine can be repeated periodically to account for seasonal changes or substrate ageing.

Signal Interpretation and Soil Health Classification: Once live signals are acquired during testing, the firmware compares them to the stored calibration profiles. The deviation between the current signal and the baseline is calculated and used to classify the soil health status. If the deviation is minimal, the soil is considered healthy and the LED displays green. Moderate deviations trigger an orange light, indicating transitional or mildly stressed soil. Significant deviations result in a red light, signalling degraded, compacted, or contaminated conditions. This classification system provides immediate, intuitive feedback to the user without requiring external devices or data analysis.

Display and Data Sync: After signal interpretation, the central body displays a summary of soil health across all four fungal probes. This can be shown via an OLED screen or a colour-coded LED strip, depending on the device configuration. If wireless connectivity is enabled, the firmware transmits the data to a paired mobile app or cloud dashboard for logging, visualisation, and long-term tracking. Each test result is timestamped and stored locally, allowing users to review historical data and monitor trends over time. Firmware updates and calibration profiles can also be synced remotely, ensuring the system remains accurate and responsive.

Signal Interpretation: Biological Meaning

  • Ganoderma lucidum: High impedance and enzyme activity indicate nutrient-rich, biologically active soil. Low readings suggest depleted or stressed soil conditions.
  • Trametes versicolour: Elevated redox current from lactase activity signals the presence of pollutants or heavy metals. Low activity suggests clean or uncontaminated soil.
  • Pleurotus ostreatus: Strong VOC emissions and enzyme responses reflect high microbial diversity and active nutrient cycling. Weak signals may indicate sterile or imbalanced soil.
  • Mycena species: Robust biomass growth and oxygen sensitivity point to loose, biodiverse soil structures. Suppressed development suggests compaction or ecological degradation.

Field Deployment User Guide

The modular fungal biosensor system provides a practical, field-ready solution for assessing soil health. Designed for intuitive use, it combines biological sensitivity with real-time feedback. Users can monitor soil vitality, detect contamination, evaluate microbial diversity, and identify compaction by observing the metabolic signals of four distinct fungal species.

The guide below serves as a conceptual mock-up of the biosensor’s operational workflow. It outlines the essential steps for setup, calibration, testing, and maintenance, providing a framework for accurate and reliable deployment across diverse environmental conditions.

Getting Started: What’s in the Kit

The biosensor kit will include:

  • 1 × Central Handheld Unit (with display and calibration button)
  • 4 × Fungal Probe Heads (A–D): A: Ganoderma lucidum – soil vitality; B: Trametes versicolour – pollutants; C: Pleurotus ostreatus – microbial diversity; D: Mycena spp. – soil compaction
  • 1 × Calibration Tray (4 compartments)
  • 4 × Reference Soil Cartridges (labelled A–D)
  • 1 × USB-C charging cable
  • 1 × Soil sampling scoop
  • 1 × Quick-start card

Calibration Before First Use

Before testing real soil, it is important to calibrate each probe head using the provided reference cartridges. Begin by opening each cartridge and pouring its contents into the corresponding compartment of the calibration tray. Add 5 to 10 millilitres of distilled water to each compartment to create a slurry, ensuring the mixture is consistent and ready for activation.

Next, insert each probe head into its labelled compartment, typically marked A through D to match the fungal species. Press and hold the Calibration Button on the central unit until all probe LEDs flash blue to signal the start of calibration. Wait about five minutes for the fungal matrices to reactivate and for the electrical signals to stabilise. When calibration is complete, the LEDs turn off automatically.

During this process, the device stores baseline signal profiles for each fungal species, creating a reference framework that enhances diagnostic accuracy during subsequent soil testing.

Soil Sample Collection and Preparation

To ensure accurate diagnostics, begin by collecting soil samples from representative areas of your field or site. Use the scoop to gather soil from a depth of 0 to 10 cm, avoiding zones that have been recently fertilized or irrigated, as these may skew the results. For broader analysis, take samples from multiple zones and label them accordingly to track spatial variability.

Once collected, place approximately 10 to 15 grams of soil into each compartment of the testing tray. Add 5 to 10 ml of distilled water to each sample to create a slurry. Mix gently to activate microbial and fungal responses, which are essential for generating meaningful bioelectric signals during testing.

Running a Soil Health Test

With the soil slurry prepared, each probe head should be inserted into its designated compartment. Once the central unit is powered on, it automatically begins acquiring signals from the fungal matrices. The microcontroller reads electrical parameters such as impedance, redox activity, and conductivity, then compares these values against stored calibration profiles to assess soil health. After approximately five minutes, each probe’s LED will display a colour-coded result: green indicates healthy soil, orange signals moderate stress, and red reflects degraded or contaminated conditions. If the device includes an OLED screen, it will present a summary of the results, including fungal species, signal strength, and timestamp. For wireless-enabled models, data can be synced to a mobile app or cloud dashboard for long-term tracking and analysis.

The central unit operates on a rechargeable lithium-ion battery, which can be charged using the included USB-C cable. A full charge typically provides up to eight hours of active use. After each test, it’s important to rinse the probe tips and testing tray with distilled water to prevent cross-contamination. Probe heads should be stored in a cool, dry place when not in use, and the fungal matrices should be replaced seasonally or after roughly 20 tests to maintain accuracy. Although the device is built for rugged field conditions, regular cleaning and calibration will help extend its lifespan and ensure reliable performance.

For users integrating the companion mobile app, the device can be paired via Bluetooth or Wi-Fi to unlock additional features. The app enables viewing of historical data, tracking of soil health trends, and tagging of results with GPS coordinates. It also supports firmware updates and provides reminders for calibration and maintenance.

If troubleshooting is needed, a few quick checks can help. If the LED does not light up, verify the probe connection and battery level. If calibration fails, ensure the reference soil is moist and the probe is fully inserted. For inconsistent readings, recalibrate the system and confirm the soil slurry has a uniform consistency.

Advantages of Mycelial Probes by User Type

For farmers, the fungal biosensor system would offer real-time feedback on critical soil parameters such as fertility, moisture levels, and microbial health. This immediate insight helps optimise crop management and supports precision agriculture. Unlike traditional methods that rely on lab testing, the biosensor would eliminate delays and reduces costs, making it a practical tool for on-site decision-making.

Gardeners can benefit from an easy-to-use tool that monitors soil vitality and plant compatibility without requiring specialised knowledge. The biosensor simplifies soil assessment by removing the need for chemical kits or expert interpretation. Its intuitive design makes it accessible for hobbyists and professionals alike, enhancing garden planning and plant care.

Site Inspectors can use the biosensor for rapid evaluations of soil degradation, contamination, and compaction. Its portable and non-invasive nature allows for efficient field assessments, while the biologically meaningful data provides deeper ecological context. This makes it a valuable instrument for environmental audits and land-use evaluations.

Outline for a Research Programme

Phase 1: Fungal Species Selection & Cultivation (Months 1–3)

  • Select and grow Ganoderma lucidum, Trametes versicolor, Pleurotus ostreatus, Mycena spp.
  • Measure baseline electrical activity under controlled conditions
  • Deliverable: Signal profiles and cultivation protocols

Phase 2: Electrode & Signal Conditioning Optimization (Months 2–4)

  • Test electrode materials and amplifier configurations
  • Simulate signal behavior across soil types
  • Deliverable: Optimized electrode designs and circuit schematics

Phase 3: Calibration System Development (Months 3–5)

  • Design reference soil cartridges and calibration tray
  • Establish baseline signal profiles for healthy soil
  • Deliverable: Calibration protocol and reference matrix specs

Phase 4: Sensor Head Prototyping (Months 4–6)

  • Build modular probe heads with embedded fungal matrices and electronics
  • Test durability, signal fidelity, and replaceability
  • Deliverable: 4 working probe head prototypes

Phase 5: Central Hub Electronics & Firmware (Months 5–7)

  • Assemble ESP32-based control unit with USB-C charging
  • Develop firmware for signal acquisition and LED feedback
  • Deliverable: Functional central hub and firmware code

Phase 6: Field Testing & Validation (Months 7–10)

  • Deploy sensor in diverse soil types and seasonal conditions
  • Compare sensor output to lab-based soil assays
  • Deliverable: Field performance report and user feedback

Phase 7: Data Analysis & Machine Learning (Months 9–12)

  • Build synthetic datasets and train classifiers
  • Integrate predictive model into firmware or app
  • Deliverable: Signal interpretation engine and enhanced firmware

Budget Estimate (EUR)

  • Lab materials & fungal cultures - €5,000
  • Electronics & prototyping - €8,000
  • Calibration system development - €3,000
  • Field testing & travel - €4,000
  • Software & data analysis - €5,000
  • Personnel (1 researcher, 1 technician) - €20,000
  • Contingency & overhead - €5,000
  • Total: €50,000

References

General Soil Sensor and Biosensing References

Low-Cost Sensor System for Soil Assessment: Describes a 3D-printed biosensor that detects fungal quorum-sensing molecules (tryptophol) to assess soil biological activity. https://www.mdpi.com/2072-666X/15/11/1293

Biosensor Technologies for Plant Pathogen Detection: Reviews biosensors for detecting plant pathogens, including fungi, with emphasis on electrochemical and optical systems. https://www.frontiersin.org/articles/10.3389/fchem.2021.636245/full

Smart Agriculture Systems: Soil Sensors and Plant Wearables for Smart and Precision Agriculture: Explores advanced soil sensors and plant wearables, highlighting the potential for biological sensing in precision agriculture. https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.202170156

Advances in Monitoring Crop and Soil Nutrient Status: Discusses limitations of traditional soil testing and the need for real-time, non-invasive biological sensing. https://www.mdpi.com/2311-7524/11/2/182

What Are the Benefits of Biological Soil Testing? Explains how biological soil testing offers a holistic view of microbial activity and soil health. https://decode6.org/articles/what-are-the-benefits-of-biological-soil-testing/

Soil Sensors: Definition, Types, and Benefits: Overview of soil sensor technologies and their role in improving soil microbiome health. https://www.thomasnet.com/insights/soil-sensors/

Soil Testing Methods for Fungal Detection: Summarizes fungal detection techniques in soil, including biosensors and molecular diagnostics. https://synapseforges.com/articles/soil-testing-methods-fungal-detection/

Fungal Species

The Impact of Continuous Cultivation of Ganoderma lucidum on Soil Nutrients, Enzyme Activity, and Fruiting Body Metabolites: Shows how G. lucidum responds to soil nutrient levels and enzyme activity, validating its use as a soil vitality indicator. https://www.nature.com/articles/s41598-024-60750-y

Traditional to Technological Advancements in Ganoderma Detection Methods in Oil Palm: Reviews detection methods for Ganoderma in soil, including biosensor applications. https://link.springer.com/article/10.1007/s12223-024-01177-w

Biodegradation of Trichloroethylene by Trametes versicolour and Its Physiological Response to Contaminant Stress: Demonstrates T. versicolour’s ability to degrade pollutants and respond to environmental stress. https://link.springer.com/article/10.1007/s00128-024-03898-7

Biosorption and Bioaccumulation Potential of Trametes versicolour in Heavy Metal Remediation: A Toxicological Perspective: Highlights T. versicolour’s capacity to remove heavy metals from soil and water. https://www.umft.ro/wp-content/uploads/2025/07/Poster-proiect-cercetare-2025_Nanostructuri-inteligente_POSTER-FESTEM-TRAMETES.pdf

Establishing Microbial Communities to Promote the Growth of Pleurotus ostreatus Through a Top-Down Approach: Explores microbial interactions and how P. ostreatus responds to soil biodiversity. https://journals.asm.org/doi/10.1128/aem.00898-25

Nutritional Profile and Microbial Analysis of Pleurotus ostreatus Cultivated on Agricultural Residues: Examines how substrate and microbial load affect P. ostreatus growth and nutrient uptake. https://ijisrt.com/assets/upload/files/IJISRT24DEC1001.pdf

In Vitro Evidence of Root Colonization Suggests Ecological Versatility in the Genus Mycena: Shows Mycena’s sensitivity to soil structure and biodiversity, supporting its use as a compaction indicator https://nph.onlinelibrary.wiley.com/doi/am-pdf/10.1111/nph.16545

Two New Mycena Section Calodontes Species: One Newly Discovered and the Other New to Japan: Highlights ecological diversity and adaptability of Mycena spp. in forest soils. https://www.jstage.jst.go.jp/article/mycosci/65/3/65_MYC625/_html/-char/en

Simulated Signal Profiles by Fungal Species

Ganoderma lucidum:  Electrical Behaviour: Slow, rhythmic oscillations with stable amplitude Supporting Source: Adamatzky, A. (2022). Electrical Frequency Discrimination by Fungi Ganoderma resinaceum. https://link.springer.com/chapter/10.1007/978-3-031-38336-6_19

Pleurotus ostreatus:  Electrical Behavior: Moderate-frequency bursts and spike trains Supporting Source: Adamatzky, A. (2022). Electrical Frequency Discrimination by Fungi Pleurotus ostreatus. https://arxiv.org/pdf/2210.01775v1

Trametes versicolour:  Electrical Behavior: High-frequency, low-amplitude pulses sensitive to pollutants Supporting Source: Adamatzky, A. (2023). Fungal Sensing of Heavy Metals Using Electrical Signatures. https://doi.org/10.1007/978-3-031-38336-6_19

Mycena species:  Electrical Behavior: Irregular, erratic spikes with high signal complexity Supporting Source: Adamatzky, A. (2021). On the Information-Theoretic Complexity of Fungal Electrical Activity. https://doi.org/10.1016/j.biosystems.2021.104373

arXiv Study  Title: Propagation of Electrical Signals by Fungi Authors: Andrew Adamatzky et al. https://arxiv.org/pdf/2304.10675

FEMS Microbiology Reviews  Title: Electrical Signalling in Fungi: Past and Present Challenges. https://fems-microbiology.org/femsmicroblog-fungi-as-natures-hidden-electrical-network

Design Strategy: Shelf-Stable, Ready-to-Use Mycelial Sensor Layer

Dehydrated Mycelium Retains Electrical Responsiveness. Adamatzky, A. (2023). Propagation of Electrical Signals by Fungi. https://doi.org/10.1016/j.biosystems.2023.104933    

Substrate and Growth Optimization for Ganoderma lucidum and Pleurotus ostreatus. Fletcher, P.V. et al. (Leeds Beckett University). Effect of Temperature and Growth Media on Mycelium
Growth. https://eprints.leedsbeckett.ac.uk/id/eprint/6111 ·      

Mycelium-Based Composites for Packaging and Construction  PLOS ONE. Effect of Common Foods as Supplements for Mycelium Growth. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0260170 

Environmental and Nutritional Effects on Mycelium Viability  Jo, Y. et al. (2024). Effects of Environmental and Nutritional Conditions on Mycelium Growth. https://www.tandfonline.com/doi/pdf/10.1080/12298093.2024.2341492

Related Patents

US20210140908A1 – Soil Moisture and Nutrient Sensor System Describes a sensor probe that uses conventional electronic components—such as capacitive and resistive sensors—to measure soil moisture and fertility. It does not incorporate biological elements like fungi or microbes. https://patents.google.com/patent/US20210140908A1/en

US20240402145 – Systems and Devices for Soil Moisture Detection Outlines a hybrid sensor system combining conductive and capacitive sensing techniques to assess soil moisture. The design focuses on accuracy and durability but does not involve biological sensing mechanisms. https://patents.google.com/patent/US20240402145/en

EP1700919A1 – Biosensor Having Soil Microorganism Housed Therein and Use Thereof Introduces a biosensor that uses viable soil microorganisms—including fungi—to detect contamination and assess soil health. The sensor relies on biological activity as a diagnostic signal. https://patents.google.com/patent/WO2005049854A1/en

If you’re interested in this idea, please contact me using the button below.

Share this page

Licence: All ideas and concepts shown on this website are shared under the Creative Commons Attribution 4.0 International Licence (CC BY 4.0) . You are free to use, adapt, and build upon them, provided you give appropriate credit to Dr. Patrick Reynolds and include a link to this website.
© 2026 Patrick Reynolds