Environmental Engineering Reference
In-Depth Information
data are of the categorical type, so it is not possible to calculate averages for the
Seamzones as can be done with for example climatic data. Instead it is needed to
select one soil profile description from the original data to represent the Seamzone.
Secondly, the mapping units of the European soil map, i.e. the so-called Soil Mapping
Units (SMUs), are described by a number of Soil Typological Units (STUs). The STUs
are described by a representative soil profile including information on the share of
it within a specific SMU. The SMUs are associations of STUs without a spatial
indication where the STUs within a SMU occur. Therefore, an overlay of the Seamzones
with the soil map (or SMUs) will not directly deliver the most dominant soil type
(STU) per Seamzone. Another problem is that it might be that the most dominant
STU actually is not representative for the soil variables that are most important
from an agricultural point of view. The following procedure was therefore adopted
to select a specific soil profile to represent the Seamzones:
1. The coverage of STUs was calculated by overlaying the Seamzones with the
SMUs and using the result for weighting the share of the STUs coverage of the
Seamzones. If for example, a STU covers 50% of a Soil Mapping Unit that
covers 25% of a Seamzone, this speciic STU covers 12.5% of the Seamzone.
2. In a second step it was decided to focus on two variables that are of high importance
for agriculture: texture in topsoil and rooting depth. The dominant combination
of these two variables was therefore calculated per Seamzone.
3. Finally, the soil dataset of the most dominant STU among the ones with the
dominant combination of texture and rooting depth class identiied under point 2
was selected as the descriptive set of soil data for the Seamzone.
The relation between the parameter used for defining the soil types (carbon content)
and the two other variables used in the selection of representative soil profiles can
be explored in Tables
7.5
and
7.6
. As can be seen from Table
7.5
there is no clear
relationship between the different soil types and the rooting depth. The share
of the different soil types that is without obstacles for roots to a depth of 80 cm is
on average 64% if the soil with no information is excluded. The only tendency
that can be seen from the table is that obstacles for roots are more often found for
the soil types with low carbon content.
Table 7.5
Shares of the area of the different soil types (characterized by organic carbon content in
%, irst column) that fall in different categories of rooting depth. The last column, 0-80 cm, contains
soil types where obstacles do occur, but the exact depth between 0 and 80 cm is not
speciied
OCTOP class
No obstacles
60-80 cm
40-60 cm
20-40 cm
0-80 cm
0.1-1.23%
59
6
19
15
0
1.23-2.46%
72
6
7
16
0
2.46-3.94%
66
12
11
10
0
3.94-5.66%
59
6
24
10
1
5.66-8.86%
67
12
15
5
0
8.86-63.0%
63
5
29
3
0
No information
51
4
22
23
0
Total
64
8
17
11
0
