Development of Prototype Soil Sensors

The aim is to develop soil sensors that provide information on soil nutrient content, moisture levels and temperature.

In crop production soil fertility is essential. In sustainable farming systems is important to minimize nutrient losses, plan the choose right cultivation timing, and reduce soil trampling. In Estonia, the conditions for nutrient leaching are favorable, because the amount of precipitation exceeds evaporation by about 1.5 times. Soils are often saturated with water in spring and are sensitive to trampling. Optimal soil moisture helps to prevent excessive compaction.

The aim of the innovation activity was to develop a prototype sensor and data exchange for measuring the electrical properties of soil with digital output, which would provide dynamic data on the following soil parameters:

  • soil salinity (nutrients) content
  • volumetric soil moisture
  • soil temperature

Practical knowledge on soil conditions help farmers  schedule fertilization, tillage and sowing.

The sensors are wireless and specifically meant to be installed underground. The sensors are able to transmit data through soil, clay, ice, snow and even stones, reaching 4 metres deep underground.

The sensors enable to obtain information on soil conditions after every 20 minutes, 24 hours a day, and 365 days a year, which makes it possible for agricultural producers to make informed decisions and act sustainably. 

The photos show wireless prototype soil sensors developed in a collaborative project, an example of a solar panel installation at base station at Rõhu, Estonia (shown on the right). Prototypes of soil sensors were developed within the framework of  “Cooperation” measure No 16 of the Estonian Rural Development Plan 2014–2020. The budget for innovation activities was 60,000 € and the project period 06.03.2017 – 20.06.2020.

Results
  1. The sensors provide continuous information on soil moisture, salinity and temperature throughout the year . The data is conveniently transferred from the field to the server.
  2. Soil sensors are very good at detecting changes in soil temperature and relative changes in soil moisture over time, but accuracy is not always sufficient to estimate absolute values. 
  3. The sensitivity of the sensors to detect salinity values depends on their installation. In order to record salinity data, the sensors must obtain  good contact with the solid phase of the soil.
  4. The addition of the solar panel is important due to distance between the soil sensors and the receiving antenna.
  5. Additional data need to be collected to provide accurate fertilisation recommendations.

On the basis of the information obtained, it is necessary to further develop the accuracy of soil sensors and to perform additional measurements and calibrations on different soils.

In the future, it will be possible to connect the data with a GIS server.

Partner: 
Soil Scout OY – Jussi Sirkiä, Johannes Tiusanen
Estonian University of Life Sciences – Alar Astover