SM150 User Manual 1
Technical Reference
32
Definitions
Volumetric Soil Moisture Content
is defined as
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
where
is the mass of water in the sample,
and
is the total mass of the
dry
sample.
To convert from volumetric to gravimetric water content, use the
equation
where
is the density of water (= 1g.cm
-3
),
and
is the bulk density of the sample (
S
S
V
M
).
M
W
M
S
W
S
g.g
-
S
W
V
V
V
S
W
V
G
