SM150T User Manual 1.0
Operation
26
General soil calibrations
Most soils can be characterised simply by choosing one of the two
general calibrations we supply, one for mineral soils (predominantly
sand, silt and clay) and one for organic soils (with a high organic
matter content).
These values have been used to generate the polynomial
conversions and linearisation tables in the
Soil moisture reading
section.
Soil-specific calibration
Instead of adopting these general calibrations, you may wish to
determine specific calibration values of
a
0
and
a
1
for your soil. This
procedure is fairly straightforward if you can get access to standard
laboratory equipment and is described in detail in Appendix 1 on
page 42.
Soil specific calibration can significantly improve the accuracy of
individual readings - but make less of an improvement to readings
where installation and sampling errors are high.
General soil calibrations
0.0
2.0
4.0
6.0
8.0
0.0
0.2
0.4
0.6
0.8
Soil Moisture
(m
3
.m
-3
)
S
o
il
r
e
fr
a
c
tiv
e
i
n
d
e
x
Mineral
Organic
a
0
a
1
Mineral soils
1.6
8.4
Organic soils
1.3
7.7
