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  • Steve Maxwell

Agritech: Soil Water Sensors

Updated: Jan 11, 2021

Steve Maxwell of Vancouver, BC champions and endorses initiatives that promote environmental preservation. Among them is the recent rise in the use and implementation of soil water sensors in agricultural technology. Hardly a novice idea, soil water sensors have been around for many years to regulate irrigation and water management in the industry. However, in the past they were proven ineffective and too expensive to warrant production due to design and functional inadequacies such as sensor failure, faulty wiring, inaccurate data collection, and excessive labour requirements. Amidst the threats of global warming, water scarcity, and the negative effects of climate change on agriculture, experts have revisited soil water sensors to combat the impending detriments of a fast-growing population and evolved models have definitely been working.

What are soil water sensors?

Soil water sensors (also referred to as soil moisture sensors) are agricultural sensors designed to aid in irrigation management. By extension, they assist in the production of more successful harvest, providing data about what is happening in the root of a crop. While there are various types of soil water sensors, they can be classified in one of two groups: the water potential sensors and the soil moisture sensors. The former measures how hard it is to remove water from the soil, providing the best indication of available water for plants and the latter records content about the soil moisture. Most soil sensors are single-point sensors—they take measurement at one location and can measure moisture, temperature, and in some instances, salinity. Some sensors may be buried in soil permanently, while others may be portable. What is most important about soil water sensors, regardless of which class each model belongs to is its effectiveness. Factors that determine that include thorough installation, installation in an area that is an accurate representation of the crop of interest with even water distribution, and the use of the sensor must operate in conjunction with other irrigation resources such as grower observation, soil moisture monitoring, and evaporation-based scheduling.

Soil water sensors are important to the work that farmers do because soil conditions are always changing and the ability to monitor those changes has a direct impact on crop management. According to Agritech Tomorrow, “soil conditions are influenced by the weather, row density, crop patterns, and more and, during this period, the plants are continuously changing and adapting to the environment.” Soil and water sensors aid in making sense of these changing conditions, providing important information in real time measurements from the field, allowing for more informed agricultural decisions with respect to crop yield.

Common soil water sensors

As previously mentioned, there are various types of soil water sensors that cater to the collection of data specific to a farmer’s needs. Among the diversity, there are standout models that are frequently used within the industry.

Tensiometer sensors

Tensiometers are one the most reliable water sensors, primarily because they collect a lot of information about what’s happening at root level. This also makes them the most high maintenance sensors. Tensiometers measure the succession pressure at the Tensiometer tip (which could either be sand-specific or clay/loam-specific). Water is either drawn out of or pulled into the tip and it creates pressure that is reflective of the force required for a plant to get its water from the soil. Readings can be conducted automatically with a pressure transducer or manually, with a vacuum gauge.

Capacitance sensors

Capacitance sensors are favourable for their ability to measure pressure at several depths, between 10 to 180 centimeters. The benefit of varied measuring is that it optimizes irrigation, indicating the sites of water penetration in the root zone. According to the Department of Primary Industries and Regional Development of Australia, “the limitation with most capacitance sensors is that they measure only a very small volume of soil outside the access tube or wall of the sensor.” This shortcoming is mitigated by proper installation that maximizes soil contact and inhibits water from running down outside of the sensor. Despite that, capacitance sensors are preferred because they are multi-point sensors.

Time and Frequency domain sensors

Sensors that measure using water content reflectometry (WCR) and time domain transmissometry (TDT) are popular, cost-effective options for time and frequency domain. These sensors are designed with two to three metal prongs (5-30cm in length) that are buried into the side of the soil pit targeting and measuring the pressure of the undisturbed soil. “The measurement extends to about 3 to 6cm around the sensor, giving a larger volume of soil measured (0.3 to 8L).” Like the capacitance sensors, proper installation is critical to maximize contact with undisturbed soil and the largest volume of soil being measured. However, unlike capacitance sensors, data from time and frequency domain sensors provide the best representation of the whole area being measured.

How to choose the best sensor for your crops

Because soil water sensors are so many and diverse in design and function, it can be difficult to determine exactly which one is best for your farm.

Some factors that should be considered during the selection process include:

  • Whether the purpose of the sensor is to determine the availability of water or the movement of water

  • Whether accuracy is important

  • Whether you prefer a sensor that is permanent or portable

  • Is the data readily available, clear, and easily understood (manual vs. automatic)


Soil Water Sensors have solidified their place in Agritech culture as the demand for efficient farming becomes increasingly emphasized. Steven Maxwell and Maxwell Capital are eager to partner with startups that work to modify and iterate soil water sensors in a manner that assists and simplifies irrigation, ultimately aiding optimal crop production.

Referenced resource:

Agritech Tomorrow:

Department of Primary Industries and Regional Development – Australia.

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