CS616 and CS625 Water Content Reflectometers
12
Figure 8-2. CS616 response for different soil types
The
compacted soil
response shows the effect of compaction and high clay
content. The signal attenuation caused by compaction or high clay content
causes an offset in the response as shown by the near-parallel curves at
water contents above 10%. This is the effect of attenuation by the solid
phase.
The effect of increased electrical conductivity for the same soil is shown
by the response curve
high EC, compacted soil
. Higher electrical
conductivity causes a decrease in the slope of the response curve. This is
the effect of attenuation by the solution phase.
8.1.2
Calibration Equations
Table
8-1
lists the calibration coefficients derived in the Campbell
Scientific soils laboratory. Both linear and quadratic forms are presented.
The choice of linear or quadratic forms depends on the expected range of
water content and accuracy requirements. These coefficients should
provide accurate volumetric water content in mineral soils with bulk
electrical conductivity less than 0.5 dS m
–1
, bulk density less than
1.55 g cm
–3
, and clay content less than 30%.
