Neutron probes and soil moisture

  • Fact sheet
  • August 2015

A neutron probe is a sophisticated and accurate piece of equipment that measures the moisture content in soil. It requires calibration and operation by a licensed operator.

The neutron probe comprises;

The nuclear unit is lowered down a stopped aluminium access tube to set depth intervals. The neutron source starts scattering fast neutrons, which are deflected by hydrogen, most commonly water, and are slowed. The source also detects and counts the returning slow neutrons. The amount of deflection is directly related to the soil moisture in the soil.


Because of their high cost and the need for a licensed operator, neutron probes are usually only bought by large organisations or consultants running a service for smaller operators.

The sphere of influence is related to the moisture content of the soil, with the neutron probe having a greater sphere of influence in drier soil. However, despite this, the neutron probe’s sphere of influence is generally greater than other systems regardless of soil moisture content.



Please note that other tools with similar functions may also be available.

More information

Speak to an irrigation consultant or your product distributor to find out how best to meet your requirements. We have developed a range of factsheets to assist you with irrigation management. See the related links below. 

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