Agriculture Reference
In-Depth Information
80
soil names
soil regr. lines oil points
70
x
Canisteo
Knoke
Nicollet
Clarion 2
Clarion 1
x
60
50
40
30
20
10
increasing differentiation between soils
0
10
15
20
25
30
35
volumetric water content in %
Fig. 5.9
Electric conductivity depending on the volumetric water content for loamy soils in Iowa,
USA (From Brevik et al.
2006
, altered)
The varying site-specific effects of texture and organic matter have been eliminated
completely by the design of the experiments, namely by sensing at exactly the same
locations at different times, and hence when the water content was not the same. So
the regressions represent only
temporal variations
that were caused by the respective
soil water content.
The results indicate that electrical conductivity has the greatest potential to
differentiate between soils when these are moist (Fig.
5.9
). Hence obtaining
reliable signals about
soil texture
is more difficult in areas where low soil moistures
prevail -
e.g.
in dryland regions without irrigation. But instead of this, the perspectives
of getting suitable information about
soil moisture
from conductivity data improve
in these areas. This is in line with results that were obtained by McCutcheon et al.
(
2006
), Neudecker et al. (
2001
) as well as Padhi and Misra (
2011
).
However, it can be questioned whether conductivity signals are the best choice
for sensing water. Methods that rely on electrical capacitance, on reflectance or on
radar waves might be better suited. For details on this see later chapters.
5.2.2.2
Electric Conductivities and Soil Properties in Arid Areas
In arid areas,
soil salinity
deserves attention. Its negative effects can be diminished or
even disposed of by site-specific, georeferenced melioration or reclamation,
e.g.
by
