The PEC Tension is an easy-to-use sensor that determines the availability of water at a tree site and the water content of the soil. The results are accessed via a mobile app, displayed in an online map application or can be integrated into individual GIS solutions.
With the use of this sensor technology, users gain knowledge about the irrigation situation at the sites, they can react at an early stage and take targeted action thanks to precise determination of requirements. In this way, drought damage to trees is prevented, while at the same time the resources of water, money and personnel are conserved. The expected service life is about 3 years without interruption.

PiCUS tree measurement technology offers tree assessors a comprehensive set of diagnostic tools for the detection and assessment of defects in trees. The Tension provides information about the soil water content and the soil water tension, i.e. the plant availability of water. From this, it can be seen whether drought stress is imminent at the particular plant site and how much water is needed to counteract it.

It can be used both in the growing phase of planted young trees and for monitoring the locations of older trees. For example, during construction work or similar with lowering of the groundwater level or for individual trees or groups of trees of outstanding importance and worthy of preservation.

Tension sensors with one to six sensor elements for suction tension and/or one sensor element for soil moisture can be used. In addition to the water tension sensors, a soil moisture sensor can be connected to measure soil moisture, conductivity, and temperature. Combining data from both sensors generates watering recommendations that enable resource-efficient irrigation. This helps minimise the risk of over or under-watering. Additional parameters required include the size of the tree disc, soil’s available water holding capacity, and the depth of root penetration. Cable length options are 1.5m, 3m or 10m for the tension and 2m for the humidity sensors. The arrangement of the sensor elements in different soil depths or different positions is freely selectable within the scope of the cable length. One or more sensors can be installed per tree, depending on the measurement target. It is also possible to install sensors at representative locations and apply the results to the group.

The central electronics can be mounted above ground, for example, on the planting support of a young tree, or buried. Using an earth auger and the IML installation aid, the sensors can be positioned accurately.

The Tension operates in a networked environment to provide the desired data remotely at any time. The hub of this network is the PiCUS Environmental Cloud.
The actual Tension sensor is installed at the tree and sends measurement data from the electronic box to the cloud. Master data of the sensor, the associated tree and the installation situation are stored in the cloud via the PEC.Service app.

The data collected in the cloud can be viewed on the move with the PEC.app. For a better overview and extended evaluations, a web GIS application is available, i.e. a map view of the measurement results accessed with a computer on the internet. Users of specific tree cadastre software have the option of integrating the results into their system via the web feature service offered, a largely universally compatible format.

The fact that drought is an essential problem for trees, especially in urban locations, has long been established in the minds of experts. Nevertheless, questions about the actual availability of water or the optimisation of irrigation often have to resort to estimates. Individual users of measurement technology may face the challenge that only limited experience and reference values are available.
As the PiCUS Environmental Cloud potentially accumulates a large number of measured values on these issues, it will also be used to generate swarm intelligence by making measurements from a large number of sites accessible to experts.
To contribute to this, each user can voluntarily give consent for the measurement data to be made visible to other users on an anonymised basis.
This does NOT reveal where sensors are located, who owns them or when and who made entries.
What would be visible is information on the type and condition of the tree as well as on the soil and installation situation, and of course the actual measurement data.
Sharing this information enables tree owners or managers to find reference values for their own measurements, for example by looking at trees of the same species or age, or sites with the same main soil type, in the same country or climate zone.

In this way, all users will be able to benefit from each other’s experience and optimise the treatment of their trees.
As such a database only becomes truly valuable through the contributions of all participants, we hope for generous participation!

Standard scope of delivery:

• Central electronics unit (sensors need adding)
• 3 years of Cloud support
• PiCUS Environmental Cloud
• PEC.Service app
• Web-GIS

Measuring principle:

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.

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 even at relatively low pF values drought stress occurs.

Depending on the application, the following components can be individually configured when ordering:

There are LTE and LoRaWAN variants of the Tension system available.

Accessories

• Installation aid 120 cm
  Installation aid to place the sensors in the soil
• Cable protection 50cm
  Metal protective hose as cable protection for above-ground installation, e.g., during mowing
• Pointed probing rod 30cm
  Can be used as a probing rod in combination with the installation aid
• Earth auger 30 mm x 1000 mm

IML GIS

In the WebGIS, there’s the capability to filter data, export it in various formats for further external processing, and integrate it into external software solutions. Automatic forwarding from the IML Cloud to a client-owned database is possible, enabling data integration into existing infrastructures such as a cadastre database.

IML GIS Reporting

The measurement data can be filtered, for instance, by pF value, and this can generate a clear Excel file. This presents a clear view of which trees require watering.

IML APP

The IML APP is necessary for setting up the system and documenting water inputs, such as:

• Tree parameters
• Soil parameters
• Number of sensors and sensor depth
• System location (displayed in IML GIS)
• Data query for current status, etc.

IML Cloud

With the LTE variant, sensor measurements are taken every hour, and the stored data is sent to the IML Cloud every 12 hours. This transmission interval allows for up to three years of operation without needing to replace batteries. The data stored on the server in Rostock is processed and visualized in IML GIS or the IML APP.

LoRaWAN Options

In a client-owned LoRaWAN network, such as in “smartcity,” the system is configured for data transfer to the client’s own data infrastructure. In this case, however, the client needs to process and visualize the data. Alternatively, if the client provides raw data to IML, it can be processed and visualized in IML WebGIS. This variant is customer-specific and needs to be requested accordingly.

Forwarding data from a public LoRaWAN network, like “thethingsnetwork” (TTN), to PEC is possible to view the data in IML-WebGIS. This offers the advantage that the client can utilize the LoRaWAN variant without needing to develop, purchase, or set up their own visualization and evaluation software. However, the availability of a TTN network is required. (Please enquire separately for this option)

Shared Comparative Database (optional)

During setup, IML Cloud provides the function of making data available on a comparison platform for measurement values. Property owners can access data on comparable trees or sites through the database, providing references for their own evaluations and planning. Only data about the tree and installation situation are visible, never about the user or location. Participation in the comparative database is voluntary.

Sustainability

The system is designed for continuous use for up to 3 years. The transmitter unit can be reused by replacing the battery. Since the Watermark soil tension sensors remain in the soil, they need replacement and expert reconnection to the transmitter unit.

See attached files for more information.