Geoscience Reference
In-Depth Information
Norway (www.planteforsk.no). It is often argued that
a priori
information on soil variation could be
useful when deciding where to take soil samples, which in practice are limited in number, due to
the high costs of soil analyses. The information provided by such EM-EC
a
maps may also be used
to divide a field into different management units, where each unit is more homogeneous in terms
of soil properties than the field as a whole (Kitchen et al., 1999). Each unit could then be managed
individually to adjust for variation between the management units.
The result of a commercial soil survey is normally a color map, showing zones with different
EC
a
. A crucial question is whether the zones on the soil survey maps show substantial differences
in soil properties. This question cannot be answered in general, but should be tested for different
soil types. In this study we wished to test whether the standard procedure used for commercial soil
survey with the EM-EC
a
method in Norway may provide maps that show significant differences in
soil properties.
13.2
MAteRIAl And MethodS
13.2.1 l
o c a t i o n
A 32 ha agricultural field located at Løten in SE Norway (60°50′ N, 11°18′ E, 315 m above sea level),
typical for the higher regions around lake Mjøsa, was selected for this case study. The field is char-
acterized by considerable variations in topography, with peaks and hollows spread over the area,
with a maximum height difference within the field of about 20 m. The soil, which is of morainic
origin, ranges from imperfectly drained brown earth (Gleyed melanic brunisoils, Canada Soil Sur-
vey) mainly at the peaks, to humified peaty gley (Terric Humisol, Canada Soil Survey), mainly in
the hollows. (See Table 13.1 for mean values and ranges of the soil properties.)
tAble 13.1
Soil properties and their Correlation (
r
) with eM
h
Soil property
Mean
Min
Max
Unit
n
r
p
Ignition loss
115
30.0
390
g kg
−1
310
0.830
<0.001
Soil organic matter
96.0
10.0
443
g kg
−1
310
0.819
<0.001
pH
7.04
5.50
8.00
g kg
−1
310
0.128
0.024
P-AL
0.10
0.02
1.35
g kg
−1
310
−0.015
n.s.
K-AL
0.07
0.02
0.15
g kg
−1
310
0.155
0.006
Mg-AL
0.11
0.03
0.32
g kg
−1
310
0.325
<0.001
Ca-AL
8.09
0.90
51.7
g kg
−1
310
0.226
<0.001
K-HNO
3
0.29
0.10
0.68
g kg
−1
310
−0.226
<0.001
Na-AL
0.02
0.01
0.08
g kg
−1
310
0.405
<0.001
Soil water content
248
134
535
g kg
−1
154
0.835
<0.001
Coarse sand
63.0
15.0
128
g kg
−1
40
−0.520
0.001
Medium sand
164
97.0
267
g kg
−1
40
−0.475
0.002
Fine sand
175
127
266
g kg
−1
40
−0.506
0.001
402
257
634
g kg
−1
40
−0.520
<0.001
Total sand (60-2000 μm)
Silt (2-60 μm)
424
294
634
g kg
−1
40
0.636
0.001
174
24.0
282
g kg
−1
40
0.006
n.s.
Clay (<2 μm)
K
+
0.16
<0.01
0.36
cmol
c
kg
−1
21
0.174
n.s.
Mg
2+
0.78
0.43
1.40
cmol
c
kg
−1
21
0.662
0.001
Ca
2+
31.0
7.25
61.0
cmol
c
kg
−1
21
0.825
<0.001
Na
+
0.04
<0.01
0.07
cmol
c
kg
−1
21
0.432
n.s.
H
+
2.50
<0.01
7.10
cmol
c
kg
−1
21
−0.127
n.s.
Cation exchange capacity
34.5
12.4
63.7
cmol
c
kg
−1
21
0.837
<0.001
