Soil moisture - FDR (profile probe)

Parameter to be measured:

Soil moisture. Permanent soil moisture monitoring along a soil profile.

Method:

FDR - frequency domain reflectometry

Equipment:

• Delta-T Device: Profile probe (PR2)
• Sentek distributed by Campbell Scientific: EasyAGII
• Sentek distributed by Campbell Scientific: EnviroSMART

Advantages:

• measures soil moisture in 4-16 depth with depth of 1m (PR2 and EasyAGII) or of 2 m (EnviroSMART) .
• manual as well as continuously logged measurements possible

Disadvantages:

• Each sensor has to be calibrated
• The application of sensor in stony soils is very limited
• The soil is always disturbed after installing the pipe. So you have to wait at least a month to get "real" measurements

What to watch out for:

• The access tube for the probe needs to be very carefully installed. There should be no air gap between the access tube and the soil!
• If you have access tubes installed in the field, but are taking only manual measurements from time to time (i.e. the probe is not continuously inside the access tube) make sure to check for condensated water inside the tube before making measurements.
• Test each sensor along the probe by covering one after the other with a wet cloth and taking a measurement, just to see if there is a reaction.
• Look at the data carefully. Test if there is a preferential flow between pipe and soil.

Links

Projects that used the above equipment:

• http://brandenburg.geoecology.uni-potsdam.de/projekte/malalcahuello/index.php

Other related web sites:

• http://en.wikipedia.org/wiki/Frequency_domain_sensor

• Delta-T Devices: Quick Start Guide
• Delta-T Devices: User Manual
• Delta-T Devices: Augering Manual

• Campbell Scientific: Brochure
• Campbell Scientific: Manual
• Campbell Scientific: Installation Guide