TABLE OF CONTENTS

• Device
• Specification
• Application
  • Data Transmission
  • Sensor Installation Preparation
  • Sensor Preconditioning
  • Sensor Installation
  • Sensor Activation
  • Sensor Removal
  • Water potential Analytics
    • Range of water potential
    • What is the impact of soil on water potential?
    • Water potential thresholds by soil type

Device

The sensor is available in various lengths. The stardard length is measuring up to 15cm while longer versions can measure up to 1 meter depth (see figure below).

Specification

Application

This sensor is intended to be used in soil. It measures temperature and soil moisture. The sensor may only be used in accordance with this manual for handling.

Data Transmission

In France, Switzerland, Belgium, the Netherlands, United Kingdom & Ireland, Denmark, Spain and Sweden a country-wide or partial LoRa network is available. The sensors are thus expected to send live data except for some areas where coverage might not be given. In all other countries the sensors will log the data (up to 6 months), or a local network will be established. If the sensors are used in logging mode, data will be uploaded once the sensors are either sent back to Cital or to a defined collection point.

Sensor Installation Preparation

This section describes the intended handling of the sensor. Please follow the instructions closely.

For the installation the material specified below is required:

• Sensor(s)

• Bucket

• Shovel, earth screw or similar digging tool 

• Water

• Mobile phone or computer

Sensor Preconditioning

Before the sensor is installed, the Watermark sensor needs a certain preconditioning in water. Once a sensor was out of the soil for two days or more, preconditioning should be performed again. This is done to improve sensor response during the first few irrigations. To correctly set up the sensor, the following steps should be completed:

During the soaking procedure the whole metal part of the sensor should be covered in water.

Sensor Installation

Good locations for positioning of the sensors are the check plots of your field (if available), one sensor per plot, within a row, if not required differently within the scope of the work.

For sensor installation, a hole of the required depth needs to be made. Its diameter should slightly exceed the sensor diameter (25mm/1”). Once the hole is prepared, the sensor can be placed.

To place the sensor at the desired depth, keep an eye on the marks you can see on the sensor (see figure below). You will be able to enter the amount of marks still visible after planting the sensor in our system (under attributes), this way the system knows how deep the sensor was dug in. If you know the required depth and want to calculate the number of marks that must be visible for the respective depths.

The calculated depth is measured from the center of the watermark sensor to each mark on the shaft of the housing.

Example: If you intend to place the middle of the watermark sensor at 14 cm deth/5.5 inch you need to make sure that the top mark is at soil level (0 visible marks above soil level). If your intention is to place the middle of the sensor at 6.5cm depth (minimal depth) the first mark should be at soil level and 5 additional marks should be visible.

If not desired differently, or not stated otherwise: place the sensors at 14 cm depth.

To finish the physical sensor placement, mud is produced by mixing field soil with water. The space around the sensor is then filled with the mud (see figure 7 & 8). If necessary, some additional soil is added, so that the sensor can not wiggle anymore.

These general rules should be followed when installing a sensor into the ground:

1. The soil in the area surrounding the sensor should not be excessively compacted/hardened. This can be avoided by digging a hole large enough to easily fit the sensor.

2. The sensor must have full contact with the surrounding soil, this is very important to make sure the collected data is useful.

Sensor Activation

Once the sensor is physically installed, an activation time frame can be set on our platform Cital Insights. This will crop the view of the data to the time that the sensor is installed in a particular setting. You can use your mobile phone to scan the QR code on top of the sensor or conduct the activation via the Cital Insights page on your computer either before or after the physical sensor placement in your trial. If you choose to activate the sensors via computer, you need to make sure that you know which Sensor/Device ID was placed at which position. 

Please note that the activation of the sensor does not impact the collection of data. Our sensors measure data no matter whether they are in the ground or not. The activation merely sets the time frame in which we display the data to you. This can be modified at any moment and no data captured will be lost.

During the activation, the following information will be requested:

Sensor Removal

If a use period is concluded or you need the senors somewehre else, carefully remove them from your field by excavating them. When advised to return them, see our Return Shipments page.

Water potential Analytics

Range of water potential

The range of the sensor to capture water potential is 0 to -252 kilopasquale (kpa). On this scale, 0 would display a state in which the sensor is put in a glass or bucket of water. If you were to stick the sensor in a bucket of sand and continually applied heat, you would see measurements of -252 kpa, meaning completely dry.

What is the impact of soil on water potential?

The interpretation of water potential must always be in relation to the soil type the sensor is placed in. This means that a given measurement, e.g. -35 kpa, has a different meaning from one soil type to another.  

Water potential thresholds by soil type

Depending on your soil type, the thresholds of field potential, upper optimal, lower optimal and stress level will be different. To read the thresholds according to your soil type, we have put together a handy table to use below.