Difference between revisions of "Soil moisture - impedance method (Theta Probe)"
| Line 11: | Line 11: | ||
==Advantages:== | ==Advantages:== | ||
| − | *easy and fast measurement of punctual soil moisture | + | * easy and fast measurement of punctual soil moisture |
| − | *manual as well as continuously logged measurements possible | + | * manual as well as continuously logged measurements possible |
==Disadvantages:== | ==Disadvantages:== | ||
| − | *Each sensor has to be calibrated | + | * Each sensor has to be calibrated |
| − | *careful application of probe in stony soils | + | * careful application of probe in stony soils |
| − | *Underestimating of permitivity in media with low permitivity (ε > 40, clay and organic soils) | + | * Underestimating of permitivity in media with low permitivity (ε > 40, clay and organic soils) |
| + | * unaccuarate values in saturated media | ||
==What to watch out for:== | ==What to watch out for:== | ||
Revision as of 12:06, 18 December 2008
Parameter to be measured:
Soil moisture, permitivity
Method:
Impedance-method
Equipment:
- Delta-T Device: Theta-Probe (ML2x) with 4 rods of 600 mm length, HH2 display for manual reading or a data logger
Advantages:
- easy and fast measurement of punctual soil moisture
- manual as well as continuously logged measurements possible
Disadvantages:
- Each sensor has to be calibrated
- careful application of probe in stony soils
- Underestimating of permitivity in media with low permitivity (ε > 40, clay and organic soils)
- unaccuarate values in saturated media
What to watch out for:
- Good contact between probe and medium has to be proved
Problems/Questions:
Links
Other related web sites:
- John Miller Theta Probe: Theta Probe ML2X Principles of operation and application
- Delta-T Devices: User Manual
- Test of 5 different soil moisture sensors
- sowacs.com - the central resource for soil moisture measurement
References
Blonquist, JM; Jones, SB; Robinson, DA. 2005. Standardizing characterization of electromagnetic water content sensors: Part 2. Evaluation of seven sensing systems. VADOSE ZONE JOURNAL 4 (4): 1059-1069.
Gaskin, GJ; Miller, JD. 1996. Measurement of soil water content using a simplified impedance measuring technique. JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH 63 (2): 153-159.
Miller, JD; Gaskin, GJ; Anderson, HA. 1997. From drought to flood: Catchment responses revealed using novel soil water probes. HYDROLOGICAL PROCESSES 11 (5): 533-541.
Seyfried, MS; Murdock, MD. 2004. Measurement of soil water content with a 50-MHz soil dielectric sensor. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL 68 (2): 394-403.