Definitions
Volumetric Soil Moisture Content
is defined as
θ
V
W
S
V
V
=
where
V
w
is the volume of water contained in
the sample
and
V
s
is the total volume of the soil sample.
The preferred units for this ratio are
m
3
.m
-3
, though
%vol
is
frequently used.
Soil Moisture Content varies from approx. 0.02 m
3
.m
-3
for sandy
soils at the permanent wilting point, through approx. 0.4 m
3
.m
-3
for clay soils at their field capacity, up to values as high as 0.85
m
3
.m
-3
in saturated peat soils.
Gravimetric Soil Moisture Content
is defined as
M
where
W
is the mass of water in
the sample,
and
M
S
is the total mass of the
dry
sample.
θ
G
W
S
M
M
=
g.g
-1
To convert from volumetric to gravimetric water content, use the
equation
θ
θ
ρ
ρ
G
V
W
S
=
*
where
ρ
W
is the density of water (= 1),
and
ρ
S
is the bulk density of the
sample (
=
M
V
S
S
).
Organic and Mineral definitions:
The generalised calibrations have been optimised to cover a
wide range of soil types, based on the following definitions:
optimised
bulk
use for
use for
Soil type
around
organic
content:
organic
contents:
density
bulk
range:
densities:
-3
(g.cm )
-3
(g.cm )
Mineral ~ 1 %C
< 7 %C
1.25 - 1.5 > 1.0
Organic ~ 40 %C
> 7 %C
0.2 - 0.7 < 1.0
Profile Probe User Manual
3.0a
Technical reference
z
29
