Geoscience Reference
In-Depth Information
High
foc
Low
foc
1999-2001 Sample sites
2003 Sample sites
Wiggins 1
Wiggins 2
Yuma
fIGURe 15.1
Map of
f
oc
variability in three fields in Colorado based on regression tree analysis between
f
oc
and EC
a
.
f
oc
= (Soil Organic Matter * 0.58) g/100 g
(15.3)
Analyses of the relationships between soil EC
a
, herbicide
K
d
values, and various soil proper-
ties were done using linear regression functions in SigmaPlot v 7.101 (SPSS Inc., Chicago, IL). For
each field, regression tree analysis was performed on the soil EC
a
and
f
oc
values using the S-Plus
tree analysis tool of S-Plus2000 (Insightful Corp., Seattle, WA) to establish EC
a
-
f
oc
relationships
for mapping
f
oc
classes in the fields. Due to the small size of the data sets for the individual fields,
a check of the regression tree results was performed by a boot strapping technique (Hasties et al.,
20 01).
15.3 ReSUltS And dISCUSSIon
There were significant correlations between EC
a
and
f
oc
and between
f
oc
and
K
d
for all three herbi-
cides across all three fields (Table 15.1). These results are similar to those of Jaynes et al. (1995).
