Agriculture Reference
In-Depth Information
soil textural range
loam/ silty clay loam
loam/ clay loam
loam/ clay loam
silty loam/ silty clay loam
silty clay loam
silty clay loam
loamy fine sand
silt loam
8
r
2
= 0.60
7
6
1: 1 line
regression
5
4
4
5
6
7
8
on-the-go mapped pH, unprocessed
electr. cond. ( mS/ m )
absolute stand. dev.
9.26
11.44
14.88
3.17
16.49
25.86
0.97
3.22
5.58
2.22
3.66
1.00
4.60
4,97
0.99
1.08
8
r
2
= 0.81
7
6
1: 1 line
regression
5
4
4
5
6
7
8
on-the-go mapped pH, field specific bias removed
Fig. 9.5
Comparison between water pH measured conventionally in laboratories or sensed by
ion-selective electrodes on-the-go (Fig.
9.4
) using naturally moist soil samples. The graphs are
based on records from eight fields within six states of the USA. The data in both graphs are from
the same fields, but differ in the processing as explained in the text (Extracted from Adamchuk
et al.
2007
, altered)
results for potassium and nitrogen. From Fig.
9.3
it can be seen that potassium
and especially nitrate nitrogen react on the water content in the samples. But the
coefficients of determination (r
2
) for the soil water pH were even better than
those in Fig.
9.5
.
In all these experiments, soil phosphorus was not included. Up to now, sensing
this nutrient with ion-selective electrodes has not been successful. Reasons for this
are dealt with later.
9.2.3
Sensing Nitrate in Slurries of Soil
Sensing in slurries or in liquid extractions of soils by
ion-selective electrodes
is
being practiced in laboratories. In an on-the-go operational mode, up to now neither
