Agriculture Reference
In-Depth Information
0
50
m
100
6
6
6
2
2
2
2
5
5
4
4
1
1
4
N
5
6
6
3
3
4
4
3
3
6
2
2
4
4
2
1
1
1
1
4
4
5
5
5
6
2
2
3
3
3
3
electrical conductivities in mS/ m (see numbers)
1 < 20 2 20.1 - 30
1 < 20.0 2 20.1 - 30.0
3 30.1 - 40
3 30.1 - 40.0
4 40.1 - 50
4 40.1 - 50.0
5 50.1 - 60
5 50.1 - 60.0
6 > 60.1
6 > 60
Fig. 5.13
Maps of three repeated recordings and of the mean signals that were obtained from
these (From Mertens et al.
2008
, altered)
5.2.2.4
Perspectives for the Use of Electrical Conductivities
For
humid regions
, clay- and water content of the soil are the main factors that
define the site-specific electrical conductivities. Whereas the clay content is con-
stant on a time basis, the moisture changes steadily. The temporally varying site-
specific signals hence are mainly the result of the changes in water content. An
effective method to even out these temporal variations resulting from the transient
water factor is to record signals online and on-the-go at different dates and then to
create maps that rely on mean data per cell. A prerequisite for this method is precise
georeferencing that provides accurate spatial matching of the signals.
The original maps in Fig.
5.13
were taken from the same area (field Frankenforst
in Fig.
5.8
) at different times. They show distinct similarities. But they reveal also
some differences, which probably are mainly due to temporal variations in the soil
moisture. The
map of the means
neutralizes the temporal water effect at least
partly. This procedure of averaging the results from repeated mappings must not be
expensive. A single map causes an investment of about 6 Euros per ha on a contrac-
tor basis. So the contracting expenses for three maps add up to 12 Euros per ha. The
expenditures for processing to maps of the means hardly count and hence can be
ignored. Yet relevant is that the maps can be used for many years. If the use is
