Methods to Measure Soil Moisture

Water Conservation for Lawn and Landscape March 19, 2012 Print Friendly and PDF

Methods to Measure Soil Moisture

Soil moisture monitoring can give a homeowner more knowledge on about his or her yard and how a landscape can become more water-wise. This article will outline some of the general methods and instrumentation used when measuring soil moisture.

Volumetric Field Methods- these types of testing estimate water volume from a sample of undisturbed soil.

  • Neutron Moderation- Radioactive neutrons collide with soil particles to give a proportional count of the volume of water present.
  • Advantages: accurate, inexpensive, not affected by salinity or air gaps
  • Disadvantages: safety hazard (radiation), requires certified personnel
     
  • Frequency Domain- Uses electrical current to measure soil moisture
  • Advantages: accurate, reads in high salinity, relatively inexpensive
  • Disadvantages: sensitive to air gaps and temperature, small sensing area
     
  •  Heat Dissipation- thermal conductivity is used to measure moisture in the soil
  • Advantages: wide measurement, no maintenance, not affected by salinity
  • Disadvantages: sophisticated controller needed, slow reaction time
     
  •  Dielectric Method-Electromagnetic waves are used to measure soil saturation
  • Advantages: accurate, minimal soil disturbance, soil calibration not usually required
  • Disadvantages: expensive, sensitive to salinity
Neutron moisture meter/probe. Photo credit: Texas AgriLife Research & Extension Center at San Angelo

 

 

There are many other ways to measure soil moisture. It is important to gain as much information as possible about your yard to maximize water efficiency.

More on Methods to Measure Soil Moisture

Field Devices for Monitoring Soil Water Content

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.