We took a close look at the newest soil moisture sensors, what they cost and where the technology is headed in the years to come.
In Australia, Canada, New Zealand and the USA in particular, increasing numbers of growers already have irrigation in place or are planning to use it. While it’s a substantial investment, it’s one that obviously mitigates against one of farming’s most serious annual risks, namely drought. Indeed, scientists are predicting that a ‘megadrought’ is already underway right now in the western USA.
Costs of irrigation systems reduced
However, the advent of better solar panels and batteries, Internet of Things (IoT), wide-ranging internet networks and cloud computing are reducing the costs of irrigation systems, while at the same time system capabilities are evolving.
Accurate measurement of soil moisture is obviously key but, according to Jonathan Wisler (Sensoterra), developing world agriculture is still in the early stages of integrating soil moisture sensors into irrigation systems at scale. “For many, it is still a challenge to get the right soil moisture data from the field and into a digital farming system.”
Soil moisture data
Various irrigation systems now on the market use soil moisture data to provide differing levels of automation in the creation and implementation of irrigation scheduling. We contacted 19 companies (10 of which responded) to provide an overview of what they offer and also to get their sense of future directions.
Enabling growers to control irrigation themselves
Some companies such as Dynamax focus on enabling growers to control irrigation themselves. Dynamax provides soil water content as a percentage or water-by-volume data, along with typical soil type calibration curves. Similarly, Dacom provides soil moisture, temperature and precipitation pattern for each 10 cm layer in an online platform.
Soil water tension
Irrometer’s sensors measure soil water tension, “a real-time measurement,” says Brian Bourbonnais, “that allows growers to make decisions on the fly.” Sensoterra offers a soil moisture data platform that can be calibrated to soil type and integrated with other tools to combine data from weather forecasts, temperature and other readings, allowing growers to make ‘educated’ irrigation timing decisions.
Sentek provides irrigation decision-making in real time, using measurements of soil moisture, root location, onset of plant stress and depth of irrigation application. Valley Irrigation (Valmont) takes information on applied irrigation (e.g. from pivots and linears, automatically collected from its system or entered manually) along with data from soil moisture probes and updated weather forecasts to provide recommended irrigation schedules.
Meter Group offers the ability to sense plant water availability across varying soil conditions and crop types in order to schedule irrigation. Pessl Instruments provides as much automation as a client wants in order to make irrigation decisions and Gottfried Pessl says “technically, full automation is not a problem.”
Physical soil-moisture sensors
Looking ahead, there are differences in opinion as to how long physical soil moisture probes will be used, and what’s likely to come as soil moisture sensing and irrigation systems evolve. GroPoint’s David Illing, for example, believes soil moisture probes will be required “for some time”, but that their capabilities will advance along with advances in cloud computing and wireless technologies. He thinks that at this point, “it is time to engineer (versus retrofit) new sensors that leverage proven soil moisture-sensing methods/technologies,” but also focus on “simplicity of installation.”
Need to collect quality hyper-local sensor data
Similarly, those working at Meter Group feel that, while data from soil moisture probes is still critical, it’s important to embrace “the need to collect quality hyper-local sensor data and translate that to a holistic view of the field by combining it with remote sensing and modelling systems,” explains Kersten Campbell.
Sentek’s Peter Buss also takes the view that the irrigation information system will be “multi-level.” Larissa Hendriks (Dacom) expects that in future, irrigation systems will integrate data from various sources to predict soil moisture content, but that data from soil moisture sensors will always play a role.
Fewer soil sensors in future
Wisler at Sensoterra believes growers will need fewer soil sensors in future and that it will be possible to estimate soil moisture “by using historical data about water penetration in your crop as well as soil type, combined with information from your irrigation controllers”. For his part, Andrew Olson(Valley) thinks “some emerging technologies could potentially be used in place of soil moisture probes, as growers become more accustomed to technologies such as artificial intelligence (AI) and machine learning.”
He reports that Valley is working on “a truly autonomous pivot” through a partnership with Prospera Technologies.
Communication networking
Pessl Instruments is currently using AI to analyse evapotranspiration, satellite pictures with NDVI indices, soil moisture and weather forecasts to create irrigation scheduling recommendations. Similarly, Bourbonnais at Irrometer thinks future soil moisture sensing technology for high-precision irrigation will be similar to tech in use today, but will evolve with advances in areas such as communication networking. It’s his view that newer non-contact methods so far only give a surface or very shallow penetration reference, which is not very useful for determining the irrigation requirements for a crop.
‘Full automation with IoT’
And while Vasudha Sharma believes that full automation of irrigation can be achieved with IoT and other technologies, “we are still short of research on validating the accuracy of suggestions/predictions”, as the “underlying fundamental relationships of soil water dynamics and crop response under various management systems, climates and soil types are not fully developed.”
The irrigation specialist at the University of Minnesota is excited, however, about developments such as the ‘Internet of Underground Things’: IoT sensors and nodes beneath the soil communicate among themselves about soil moisture and other plant health aspects, and of course also to above the ground to optimise irrigation scheduling. As to whether soil moisture sensors as we know them could be superseded by new technologies, Sharma believe it is possible.
Irrigation scheduling that involves no soil sensors
Lindsay Corporation, however, already offers irrigation scheduling that involves no soil sensors. With information on for example soil type, crop type, planting date and weather, the company’s software can determine both daily crop water usage and irrigation requirements, explains Albert Maurin.
