PiCUS Tension

Protect your trees from drought stress!

If rain does not occur for longer time trees are in danger of drought stress. But how serious is the situation on site? And how effective is the watering?

Use the new Tension sensor to monitor the situation in real time and organise appropriate, efficient and resource saving irrigation!

Colour scale - Simple grading of drought stress on site
Clear graphics - For detailed analysis
IoT over LTE - Daily data upload
Cloud storage - Measurement data available always and everywhere
Extendable - Configuration adaptable to individual application
Comfortable - Easy installation, no maintenance, reusable


The Tension is a sensor that is dug into the soil around a tree. It measures soil water tension at one to three positions. Soil water tension is a measure of availability of the water to the plants.

The measurement data is uploaded to the cloud storage every day and thus accessible immediately. In that way tree owners and managers can permanently keep an eye on the water availability of their plants. Drought is recognised before damage occurs and the monitoring allows to plan irrigation more efficient than ever before. As it is planned based on the actual needs, resources like labour, time and not least water are saved.



One Tension unit consists of a central electronic module and 2-4 attached sensor elements. The number of sensor elements may be chosen by the user according to the application.

The PiCUS Environmental Cloud saves all data send by the connected sensors or entered through the app. It makes all data available for access at any time so that the results may be reviewed using the App on the way or the Web GIS service on the computer.


The app is used to document the assembly situation and to check data while on the move. It is available in the respective store for free.

Data view and assessment

The Web GIS application of argus electronic GmbH displays all measuring data on a map of the area of application. In addition the data history of each sensor can be analysed. The graphic assessment functions are actively developed to add further assessment options.

Attention! In Firefox there are long waiting times when loading the map, use a different web browser if necessary!

Desktop GIS: In the near futur it will also be possible to connect established GIS software using a standardised interface to integrate the results into existing maps and create new displays.

In case of questions please contact us or the developer of your GIS.



The Tension sensors can be installed directly when planting young trees, or subsequently on existing trees that are particularly at risk or worthy of preservation.

If desired, the sensor elements can be installed at three different depths or at different positions around the tree. The central electronics can be installed above ground, for example on the stake of a young tree, or buried.

Measurement parameter

The relevant measurement result of the Tension is the soil water tension, expressed as a pF value.

The soil water tension indicates the force with which the water is held in the pores of the soil, i.e. how much force plants have to exert to get to the water. The lower the soil water tension, the more easily the water is available to plants. If the soil water tension is high, the water is hardly available to plants.

In general, a high water content of the soil tends to lead to low water tensions and a low water content to high water tensions and thus poorer water availability. However, the water content alone does not indicate whether the water can also be reached by the plants. Therefore, the Tension works with the soil water tension. This is comparable for all soil types and is a direct indicator of the situation of the plants.

Classically, soil water tensions are given as (negative) pressure, in kilopascals or hectopascals. To avoid confusion due to different units, the system basically works with the pF value, which is the decadic logarithm of the water tension in hectopascals. It takes a value between 1 and 7. For a better overview, the pF values are additionally assigned to the colours of a traffic light scale.

 pF-Wert hPa kPa  Bedeutung
4,2 16.000 1.600  Irreversible damages, Die back of plants
4,0 10.000 1.000  Drought damages must be expected
3,5 3.200 320  Serious drought stress
3,0 1.000 100  Beginning drought stress
2,5 320 32  Water available
1,8 60 6  Plenty water available

Values below 1.8 or above 4.2 are not to be expected. The classification is an approximation. Depending on the constellation of soil type and tree species it is principally possible that eve at relatively low pF values drought stress occurs.

Common comparative database (optional)

In case of the Tension the PiCUS Environmental Cloud provides an additional service, it works as a platform to compare data. Tree owners can use the database to find results of similar trees or similar sites as references for their own analyses and planning.

Only data about the tree and its surrounding conditions are visible, no information about the user or the position of the sensor. Participation in the comparative database is not mandatory but voluntary.


Tension is designed to run for about 3 years continuously.

The electronic module was intentionally constructed in a way that makes it reusable. The sensor elements are likely not to be reused after a three-year run time, also the battery will need to be replaced as it is not rechargeable.

The electronic module may be equipped after three years with new sensor elements, a fresh battery and extended cloud service and can than be deployed for another run time.