Application of Soil Temperature and Moisture Sensors in Smart Irrigation

From Flood Irrigation to Precision Delivery: How Soil Sensors Drive the Smart Irrigation Revolution

Water scarcity has become a significant challenge for global agricultural sustainability. In many regions, agriculture is the largest consumer of water, and traditional irrigation methods—relying heavily on experience or fixed schedules—often lead to water waste, damage to soil structure, and uneven crop growth. With the rapid evolution of IoT technology, Soil Temperature and Moisture Sensors are serving as the core sensing units in smart irrigation systems, pushing farming practices toward precision, intelligence, and sustainability.

By continuously monitoring the crop root zone environment, these sensors provide the scientific foundation for irrigation decisions, facilitating the leap from "watering by feel" to precise, on-demand water delivery. 

I. Beyond Intuition: Sensors Provide Critical Environmental Data

Soil temperature and moisture sensors continuously measure two crucial parameters in situ: Soil Volumetric Water Content (VWC) and Soil Temperature. These two metrics are directly related to a crop's ability to absorb water, utilize nutrients, and maintain vital physiological functions.

1. Soil Moisture (VWC): The Core Basis for "When and How Much" to Irrigate

In traditional irrigation, farmers often water based on weather forecasts, crop appearance, or fixed schedules, lacking knowledge of the actual moisture status in the root zone. This often results in:

Over-irrigation: Leads to deep percolation, nutrient leaching, and oxygen deprivation.·

Under-irrigation: Causes crops to enter a state of water stress, negatively impacting growth and yield.

By burying probes at various depths (e.g., 10cm, 30cm, 60cm), soil sensors capture the dynamic water changes within the main root zone. This data enables the setting of precise irrigation activation and termination thresholds for automated control:

When the VWC drops to a preset lower limit, the system automatically begins irrigation.·

When it reaches the predetermined upper limit, the water supply is promptly shut off, preventing over-saturation.

This closed-loop control strategy helps maintain soil moisture within the optimal range for crop growth, significantly improving Water Use Efficiency (WUE).

2. Soil Temperature: Key Factor for Root Vigor and Farm Scheduling

Soil temperature is crucial because it affects seed germination, root respiration, nutrient solubility, and microbial activity.

Optimizing Sowing Time: Certain crops have specific temperature requirements. For instance, corn sowing often requires the soil temperature at the 5–10 cm depth to be stably above a certain threshold. Continuous temperature logging assists in these critical planning decisions.

Fertigation Synergy: Low soil temperatures inhibit the dissolution and root absorption rates of key nutrients like phosphorus and potassium. By integrating temperature data, farmers can schedule fertigation (combined fertilization and irrigation) during optimal thermal windows, maximizing fertilizer effectiveness.·

Environmental Risk Alert: Continuous monitoring helps anticipate extreme temperature events (both low and high), allowing for early action such as insulation or cooling to prevent root damage. 

II. System Integration: Building the "Sense—Analyze—Execute" Smart Irrigation Loop

The value of a single sensor is limited; its full potential is unlocked only when integrated into a complete intelligent system. A typical smart irrigation system involves three key layers:

1. Data Acquisition Layer

Sensors must be strategically placed at multiple points and depths across the field to cover variations in soil type, slope, or crop types. These sensors require high stability, anti-interference capability, and long-term reliability to withstand the complex field environment.

2. Data Transmission and Analysis Layer

Collected data is transmitted via wireless communication technologies (e.g., 4G, WiFi, LoRa, NB-IoT) to a local gateway or cloud platform. The system then performs comprehensive analysis, integrating meteorological data (rainfall, evaporation, wind speed), crop growth stage information, and soil characteristics to generate irrigation recommendations or automatically execute commands.

Many platforms offer visual interfaces, allowing users to monitor real-time soil conditions, historical trends, and system status via mobile apps or desktop computers.

3. Execution Control Layer

Analysis results are sent to the irrigation control system, automatically regulating actuators such as solenoid valves, pumps, and variable frequency drives. The system can implement Zone-Specific Irrigation or Variable Rate Irrigation (VRI) based on the specific water needs of different field areas, further enhancing resource utilization precision.

III. Value Proposition: Water Saving, Quality Improvement, and Sustainability

Deploying soil sensors and a smart irrigation system delivers multifaceted benefits:

Increased Water Use Efficiency: Precisely knowing soil moisture status reduces unnecessary irrigation frequency and volume, helping alleviate water stress, especially in arid/semi-arid regions or groundwater-sensitive areas.·

Optimized Crop Environment: Maintaining suitable soil hydro-thermal conditions supports healthy root development, enhances crop resilience, and improves yield and quality stability.·

Reduced Costs and Labor: Automated control minimizes manual inspection and operation, while decreasing energy consumption (e.g., shorter pump running times), saving on operational costs.·

Supports Sustainable Practices: Prevents soil compaction, salt accumulation, and nutrient leaching caused by over-irrigation, thus protecting soil quality and reducing agricultural non-point source pollution risks.

IV. Development Trends and Challenges

Technical Evolution Directions

Multi-Parameter Integration: New generations of sensors are increasingly integrating functions like Electrical Conductivity (EC) and pH to monitor soil salinity and fertility simultaneously.·

Low-Power Design: Utilizing solar power and low-power communication protocols to enhance the convenience and sustainability of field deployment.·

Integration with AI: Leveraging machine learning algorithms to predict future moisture trends based on historical data, improving the foresight and adaptability of irrigation decisions.

Practical Challenges Faced

Long-Term Sensor Stability: Complex field conditions (salinity, humidity, biological fouling) can affect measurement accuracy, requiring periodic calibration and maintenance.·

Cost and Adoption Barrier: Initial investment costs remain high for small-scale farmers, necessitating supporting policies and technical services for widespread adoption.·

Data Standards and Interoperability: Inconsistent communication protocols among different manufacturers' devices can hinder seamless system integration.

Conclusion

The soil temperature and moisture sensor, though small, is the critical "sense organ" for the successful implementation of smart agriculture. It moves farming production from reliance on experience to dependence on data, and from extensive management to fine-tuned control.

Despite ongoing challenges in cost, maintenance, and standardization, its potential to boost water use efficiency, secure food supply, and drive green agricultural transformation is widely recognized.

In the future, as technology matures and application models stabilize, soil sensors will play an even greater role in high-standard farmlands, protected cultivation, and ecological zones, truly realizing the modern agricultural vision of "making every drop of water count."

Technology empowers the land, and data drives growth—the era of smart irrigation is here.

Soil moisture sensor datasheet:

1.NBL-S-THR Soil Temperature Moisture Sensor datasheet

NBL-S-THR-Soil-temperature-and-moisture-sensors-Instruction-Manual-V4.0.pdf

2. NBL-S-TMC Soil Temperature Moisture EC Sensor datasheet

NBL-S-TMC-Soil-temperature-and-moisture-conductivity-sensor.pdf

3. NBL-S-TM Soil Temperature Moisture Sensor datasheet

NBL-S-TM-Soil-temperature-and-moisture-sensor-Instruction-Manual-4.0.pdf

4. NBL-S-TMCS Soil Temperature, Moisture, Conductivity and Salinity Integrated Sensor

NBL-S-TMCS-Soil-Temperature-Humidity-Conductivity-and-Salinity-Sensor.pdf