Silixa Ltd

Soil Moisture Monitoring

Soil moisture content is the amount of water within a certain volume or mass of soil. Together with soil temperature is a fundamental indicator of the eco-hydrological state of a field. A precise measurement of how water and temperature are spatially distributed in soil, and their evolution in time, is crucial to the forecast and/or quantification of many key processes like plants growth, infiltration, runoff, plant and evaporation.

Commonly adopted solutions to measure soil moisture and temperature are point sensors based on time/frequency domain reflectometry.  Unless a large amount of these deployed in the soil (with consequent raise of costs and difficulty of installation and logging), most of the spatial and temporal variability of the water and temperature regimes is not captured. Fibre optic distributed temperature sensor (DTS) technology represents a cost effective solution able to provide a precise distributed monitoring of soil temperature and moisture at high spatial resolution (down to a few centimetres), over distances up to kilometres, and with minimum soil disturbance.

A DTS instrument, coupled to a heatable fibre optic cable allows for inferring distributed soil moisture applying the Active DTS method.  A low power heat pulse is sent along the cable buried in the soil at selected depth(s), and the resultant thermal response is analysed to calculate soil moisture content.

The image above shows a cable installation for soil moisture monitoring in Europe.