For Australian and New Zealand scientists, engineers, hydrologists and growers, soil moisture measurements are critical for understanding water dynamics, hydrology, soil-plant interactions, irrigation and much more. However, choosing the right tools and techniques can be challenging, given the range of options available and their various trade-offs.
Edaphic Scientific offers a comprehensive range of soil water sensing technology from world-leading manufacturers. We have a range of technology from sensors to portable meters to data logging options with internet access.
We have extensive experience with the use of soil water sensors in projects ranging from scientific research to civil and environmental engineering to agricultural and horticultural irrigation scheduling. Over many years of practical use, we have tried and tested all conceivable technology, from simple lab measurements to capacitance and TDR (time domain reflectometry) sensors, to drone technology and, on a global scale, remote sensing and satellite technology.
The soil scientists at Edaphic Scientific have years of experience in measuring soil moisture and can assist you in finding the right tool for your application. Common applications include, but are not limited to:
- Scientific research
- Irrigation management
- Sand stockpiles for cement mixing
- Turf, including sports fields and golf courses
- Soil columns and engineering research
- Mining and landfill hydrological monitoring and modelling
- Wastewater and effluent management
- Small sensors for glasshouse pots and substrate
- Profile probes for agriculture, horticulture and forestry
Edaphic Scientific is here to assist you in finding the most appropriate sensing technology for your project. In our experience, the products offered on this website are the best available in terms of value for money, accuracy, reliability, and ruggedness. Take your time to browse through the technology on this website, with the myriad application notes, videos and how-to articles. You can also contact us at any time to discuss your project requirements and for a quote on sensors, meters, or data logging options.
selecting a soil water sensor
When selecting soil water measurement methods, factors including accuracy, cost, ease of use, and how data will be accessed and used must be considered. Dielectric sensors are a popular choice for continuous monitoring of soil water content. Tensiometers, or matric potential sensors, are another option, but these measure soil water potential, suction, or tension. Gravimetric sampling and laboratory measurements is a straightforward, low-cost method but is labour-intensive and does not allow for real-time data.
By evaluating the advantages and limitations of available soil moisture monitoring tools, Australian and New Zealand users can balance precision, practicality, and budget for the best outcome.
soil moisture sensors: how they work to measure water content
Soil moisture sensors allow you to monitor water content in the soil. They use probes inserted into the soil to measure either volumetric water content or soil water tension (also referred to as suction or soil water potential).
capacitance and time domain reflectometry (TDR) sensors
These sensors transmit an electronic signal through the soil to determine its volumetric water content. Capacitance sensors create an electronic field that is disrupted by the presence of water, allowing water content to be calculated. TDR sensors measure the speed at which an electronic pulse is transmitted through the soil, which depends on how much water is present. These sensors typically provide a wider measurement range than tensiometers but often at a higher cost.
For further information, the following video demystifies soil water content methods:
Tensiometers are sensors that measure soil water tension, which indicates how tightly water is bound to soil particles. They consist of a sealed tube with a porous ceramic cup at one end that is buried in the soil. As the soil dries out, water is drawn from the tube through the ceramic cup. By measuring the vacuum created, the tensiometer indicates when plants may be stressed from lack of water. However, tensiometers only work in a limited soil moisture range and require frequent maintenance. In this article, a simplified explanation of tensiometers is provided.
In summary, while soil moisture sensors can provide useful data to help optimize irrigation, their limitations and maintenance requirements must be considered based on individual needs and budgets. When choosing a sensor, keep in mind factors like accuracy, power requirements, and compatibility with available data logging systems. With the range of tools now available, there are options for both small and large-scale soil water monitoring.
Soil water content sensors allow you to monitor soil moisture levels and make data-driven irrigation decisions. Using these devices offers several benefits:
- Accurate and real-time data. Sensors provide precise, continuous measurements of volumetric water content so you know exactly the volumetric water content in soils. Accurate and real-time data are beneficial for growers as well as geotechnical engineers, hydrologists, and plant physiologists.
- Optimized water usage. By tracking soil moisture levels, growers can determine the optimal amount of water for crops and avoid over- or under-watering. This helps maximise crop yields while minimising water usage. Some sensor systems can even be integrated with automated irrigation systems.
- Informed management decisions. The data from soil moisture sensors allows users to make science-based decisions about irrigation scheduling, planting timing, and other crop management practices.
- Scientific research. For those in agricultural, physiological, hydrological or environmental research, soil water content data provides insights into how different crops, soils, and climates influence water uptake and availability. This information can be used to develop improved water management practices and better use of scarce resources.
While soil water sensors offer substantial benefits, there are some limitations to consider regarding initial costs, installation, and maintenance for the systems. Still, the potential advantages of optimised irrigation, reduced water usage, and better crop management may outweigh the drawbacks for many operations. Using data to drive your irrigation decisions is key to improving sustainability, efficiency, and productivity.
limitations and challenges of soil moisture monitoring
Soil moisture monitoring, while providing valuable data, also presents some limitations and challenges to be aware of. Below is a summary, but click here for a comprehensive analysis of this topic.
The accuracy of soil moisture sensor measurements depends on proper calibration for specific soil types. Sensors must be calibrated to account for differences in soil texture, bulk density, salinity, and temperature. The TEROS range of soil sensors, manufactured by the world-leading technology company METER Group, are supplied with a range of calibration equations for various substrates, including agricultural soils, substrates used in glasshouses, and more.
Generally, for irrigation and agricultural applications, the calibration supplied by METER Group is sufficient and no further calibration is required. For scientific research and engineering applications, where high-precision data is required, it is recommended that users calibrate the soil sensors for their soil type.
limited spatial resolution
Most commercially available soil moisture monitoring systems provide measurements for a limited number of locations, typically just a few sensors per system. These point measurements may not accurately represent the spatial variability of soil moisture across an entire agricultural field or research site.
Capacitance and TDR style sensors, as well as soil water potential sensors such as tensiometers, only measure a short distance from the sensor surface – usually less than a few centimetres. Researchers, engineers and growers must keep this in mind when interpreting soil water content data. The following figure shows an idealised measurement volume for the METER Group TEROS 10 sensor. Other TEROS sensors have a similar measurement volume.
data interpretation challenges
The data generated from soil moisture monitoring systems require interpretation to translate into meaningful information for decision-making. Extracting insights from large, high-frequency data sets can be difficult without proper analysis tools and expertise. Data interpretation is also highly dependent on understanding the context of the measurements, including factors like weather, soil conditions, and plant water needs.
While soil moisture monitoring technology provides valuable data for understanding and managing land and water resources, users must go into implementation with realistic expectations of the limitations and challenges associated with these systems. With proper calibration, maintenance, and data analysis, the benefits of monitoring can be fully realised.
The ZENTRA Cloud Platform aims to simplify the data analysis process. When TEROS sensors are connected to the ZL6 data logger, there is an option to upload data via the internet to the ZENTRA platform. Within ZENTRA, there is the capability to generate a range of charts and graphs with various time series. You can discover more about ZENTRA here.
comparison of soil water measurement techniques: sensors vs. manual methods
Soil water content can be measured using a variety of sensors and manual methods. Each technique has its own advantages and limitations, depending on your specific needs and resources.
Soil moisture sensors provide continuous, automated measurement of soil water content. Capacitance and time-domain reflectometry (TDR) sensors are popular options. Capacitance sensors are affordable but can be inaccurate in high-salinity soils. TDR sensors are very accurate but tend to be more expensive. Installation of sensors may disturb the soil and impact measurements. Sensors also require maintenance, calibration, and data logging equipment, which adds to costs.
Manual methods like gravimetric sampling, neutron probes, and tensiometers are also used to determine soil water content. Gravimetric sampling, where soil samples are weighed before and after drying to measure water loss, is inexpensive but labour-intensive and does not provide real-time data. Neutron probes require a radioactive source, specialised training, and access to the probe, which is typically quite expensive. There is also a significant storage and disposal cost for neutron probes because of the radioactive source. Tensiometers measure soil suction, which can then be related to soil water content. They directly measure soil water availability to plants but can be difficult to install and maintain.
In summary, while soil moisture sensors tend to be more convenient by providing automated, real-time measurement, manual methods should not be overlooked as they can provide critical ground-truth data. An ideal monitoring program would utilise a combination of automated sensors and periodic manual sampling. By comparing multiple measurement techniques, users can identify potential inaccuracies and correct for them to improve the reliability of their soil water monitoring program.
future innovations in soil water monitoring technologies
Soil water monitoring technologies continue to improve rapidly, providing farmers and researchers with an increasing array of tools to optimise irrigation and gain insights into crop water stress. Several promising innovations on the horizon could further enhance monitoring capabilities.
passive microwave sensing
Passive microwave sensing measures natural microwave emissions from the land surface to estimate soil moisture over large areas. Satellites like NASA's Soil Moisture Active Passive use radiometers to monitor soil moisture globally at a coarse resolution. Continued improvements to spatial resolution and calibration could make this a valuable tool for precision agriculture.
Lidar, which stands for Light Detection and Ranging, uses laser light pulses to measure the distance between the sensor and the target. Lidar mounted on satellites, aircraft, or unmanned aerial vehicles (UAVs) can generate high-resolution topographic maps and 3D models of landscape features like vegetation canopy height. These data can provide indirect estimates of plant-available water in the soil. Ongoing hardware and software advancements are enhancing lidar's accuracy, affordability, and ease of use.
Machine learning algorithms have the potential to extract new insights from existing soil sensor data. Techniques like neural networks, random forests, and support vector machines can detect complex patterns in large datasets that humans may miss. Machine learning models could help identify leading indicators of drought stress, optimise irrigation schedules, or predict crop yields. However, machine learning requires large amounts of high-quality training data, which can be difficult to obtain for soil water monitoring.
An emerging technique called quantum gravimetry uses laser interferometry to measure tiny changes in gravity caused by soil moisture variations. Extremely sensitive quantum gravimeters could provide precise, continuous soil water content measurements over large areas. Though still mostly experimental, quantum gravimetry may someday enable breakthrough capabilities for precision agriculture and drought monitoring. Significant technical hurdles remain, but continued progress could make this an innovative tool for the future.
In summary, there are many options available for monitoring soil water content and each has its pros and cons. The team of scientists and engineers at Edaphic Scientific are here to assist you in navigating through all the options to find the most appropriate solution for your project. Contact us today for further information and assistance.
articles on soil moisture monitoring
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