Sensoterra sensors use the latest in internet of things (IoT) technology to offer hourly, precise soil moisture data, and translate the data into actionable insights. Key features like the simple, robust design, hammerability and super long battery life, make this a practical sensor built for the field. Technology features include standard built-in LoRaWAN connectivity for a durable and long-lasting sensor.
Once a soil moisture measurement has been taken we need to get that data out of the field and make it available to the user in real time. Sensor measurements are forwarded by the LoRaWAN network to the Sensoterra backend to be decoded, calibrated and interpreted. The difference with conventional IoT sensors is that we provide calibrated and interpreted data, and we can push it straight into ANY platform or automated solution. Using our energy efficient, patented measurement method, our sensors send uplinks every hour.
- Hourly EC values are measured in the field with wireless sensors
- Data is sent to Sensoterra servers via LoRaWAN network for calibration and interpretation
- Volumetric Water Content is made available via the Sensoterra Monitor App or integrated into a (custom) dashboard via the OpenAPI
We believe that our sensors are part of a bigger ‘sensor ecosystem’. We make sense of water, but there are many more parameters to be measured. And we understand that a farmer, landscaper or crop consultant does not continuously want to switch between different apps and platforms. For that reason we have built a strong and advanced API for easy integration with your own application, platform or dashboard.
With our API it is not only possible to retrieve the sensor measurements, it is also possible to manage all sensor settings (including choosing a calibration and setting a location) and to create and manage end-user accounts. Our API supports polling and push notifications.
Today millions of our sensor data points are routed in this way. Examples of existing integrations include those offering closed loop irrigation, Smart City, landscaping and greenhouse remote monitoring systems.
Connecting the API
The API provides two different access levels, allowing you to build the functionality into your own system and business model.
We have written a blog post to inform and to inspire you, by sharing API Integration Best Practices.
The credentials required for logging in to the API are the same credentials as from your Sensoterra account.
We have a Customer API available, which offers all functionality and a lot of flexibility. If for some reason it is not possible or desirable to route your data through our backend, we have a Portal API available which can be used to decode and calibrate the payloads by yourself. The Portal API has less functionality and less flexibility.
The Sensoterra Customer API is used to fully control settings like probe properties and location to inform, and potentially automate the irrigation process. This API is a RESTful web service using JSON SenML as the message format.
Reading the data
How do you interpret the measurements from your soil moisture sensor? How accurate is the data? Why can the moisture level be different from what you expect to see? And how can it be that two sensors next to each other are not showing the same moisture levels? Read below to understand the “why” and see the end of the article for tips and tricks on what you can do to get the most reliable data out of your field.
Understanding the measurements of your soil moisture sensors is easy. Whether you are using the Sensoterra Index (SI) or Volumetric Moisture Content (%), you can use the data sheets on our soil calibration page to see which values indicate wet and dry zones for every soil type. Use these recommended values when you define your sensor’s high and low setpoints – this will make it easier for you to make an irrigation decision.
When it comes to sensor accuracy, we are proud of our robust and reliable technology which measures soil moisture with an accuracy of within ±1.5% when used in the appropriate soil type. However, the accuracy of your data also depends on the soil characteristics in the exact spot of installation, if the sensor is in full contact with the soil and how much your soil type varies from the chosen soil calibration.
It’s likely that in a field of sensors, you may see varying soil moisture measurements. This is completely normal and can be explained by the amount of rocks and roots in the ground and the variation in soil composition across the field.
Why can measurements vary?
Imagine these 5 examples: You have 5 sensors installed in the exact same soil type, but they all show different measurements. The soil itself will absorb similar amounts of water in each example, but the sensors will also include the surrounding rocks, roots or air in the measurement. That’s why you can expect the measurements in each example to be slightly different.
Factors that can influence readings. Rocks, roots and air around soil might offset the reading – but the sensor will still work. But air covering the measuring pins will result in a 0% reading.
This is why we recommend you to use a system of sensors, rather than relying on a single data point. Using a system of sensors enables you to look at the overall trends of your field, taking field variations into account. Looking at the average soil moisture trends of your field, the data reliability goes up, and you will be better suited to decide when or when not to irrigate your field.
Example of field moisture variance. Soil moisture can vary across a field.
Tips and tricks
Use a system of sensors
This is the best way for you to ensure reliability of the data coming out of your field. Use the average of the different measurements to get the best general overview of soil moisture in that field.
Good installation practice is key
If you encounter hard resistance when hammering the sensor into the ground, try moving the sensor to a new spot – even if it is only 10 cm away, it can make a big difference. Seeing how different the soil can be – even at small distances – also explains why the readings can vary slightly.
Ensure that your sensor has good contact with the soil. The sensor should be sturdy in the soil, not wiggling.
Use the right calibration for your soil
Using wrong calibrations for your soil, will likely offset the data, however you should still be able to see the overall trends.
Different soil types have different ‘soil moisture behavior’. Every soil type has an ‘ideal’ window (percentage range) of soil moisture – which is called ‘plant available water’. At the low end, plants will wilt. At the high end (field capacity), nutrients will wash out and less air will be available for the roots. Not many people know that these windows can vary greatly, based on variations in size of the pores in the different soils. This is why calibration is so important.
The Sensoterra sensors work in all soil types. However, the right calibration is crucial for improving the accuracy and precision of the soil moisture measurements. Sensoterra has its own laboratory, based in Utrecht, where soils are analyzed to add new calibration curves to continuously improve soil moisture accuracy.
We’ve put together this reader to support your decisions on selecting the correct soil type by sensor.
Ook beschikbaar in het Nederlands!
* Sensoterra sensors have their data calibrated for the most common soil types in the market, indicated in the soil texture diagram (in blue).
Calibrated Soil Types
The following standard calibrations for the soil types and multiple variations are available: clay, clay loam, clay loam silt, saline clay, sand, sandy loam, sand, loam, loamy sand, peat and coco peat.
Select a single soil calibration from the soil triangle, or download the calibration guide for all available calibrations.
Contact us at [email protected] with any specific calibration requests.
Volumetric Soil Moisture Content
To understand soil moisture data can be simple when you know the specific volumetric water content for your soil. We’ve put together Soil Calibration Sheets based on each soil type available in our library. With this data you can clearly see the high- and low- thresholds for irrigation based on the properties of your selected soil.
Below is an example of Clay 1 (as seen in the Soil Triangle above).
What is Volumetric Soil Moisture Content? A method to provide the percent values of the soil moisture content of the soil. Also known as the ratio of water volume to soil volume.
How does it work? The Volumetric Soil Moisture percentages also follow the ‘Too Dry’, ‘Healthy’ and ‘Too Wet’ key, allowing careful management of soil moisture levels in your soil for better irrigation decisions.
How to read Volumetric Soil Moisture Content?
‘Too Dry’ zone (Orange) = not enough water in the soil for plant growth
‘Healthy’ zone (Light blue) = greatest zone to keep your soil-moisture thresholds at, for greatest plant growth
‘Too Wet’ zone (Dark blue) = too much water in the soil for plant growth
Find more information and examples of Volumetric Soil Moisture Content for each soil type on this presentation.
Note: Saturation point is the maximum volume of water that the soil can hold