Geoscience Reference
In-Depth Information
20.3 ReSUltS
Even though oats are not a typical crop in the North Platte River Valley, they were planted on the
entire irrigated farmland (except the Illinois field) in spring 2003 because of their sensitivity to the
kind of soil variability that also directly impacts yield variability. Visual comparison of the yield
and EC
a
maps (Figure 20.2) shows similarities in some location-specific patterns (a positive correla-
tion between the two), implying that the yield response was soil related.
Results from the yield and EC
a
mapping for the irrigated fields at SAREC are summarized in
Table 20.1. Mean yield and coefficient of variation (CV) across all fields were 2206 kg/ha (ranging
from 167 to 6379 kg/ha) and 39 percent, respectively. The yield map obtained from the yield moni-
tor data identifies areas of high and low yield potential (Figure 20.2b). As shown, yield variability
was significant even within individual fields as small as New Hampshire (7.5 ha). Mean EC
a
for the
top 0.9 m soil and across all fields was 34.8 mS/m (milli Siemen per meter), ranging from 0.4 to
300 mS/m. Regardless of the size of the field, soil EC
a
showed high variability (Table 20.1), with an
overall CV of 56 percent. The highest EC
a
values were observed in Illinois (mean of 50.6 mS/m),
which also had the highest clay (21 percent) and organic matter (1.46 percent) contents. As expected,
the lowest EC
a
values in Montana (mean of 22.7 mS/m) corresponded to the lowest clay (14 percent)
and organic matter (1 percent) contents. The California field contains a saline seep (saturated paste
EC = 1420 mS/m) near the southern tip of the field, clearly identified by the EC
a
mapping with
tAble 20.1
Summary Statistics of oats yield and eC
a
Measurements
across Irrigated fields at SAReC
oats Grain yield (kg/ha)
Irrigated
field
field
Area (ha)
Mean
Std
Min
Max
Cv (%)
New Hampshire
7.5
2019
720
167
6199
36
Triangle
7.6
1655
510
168
5575
31
Illinois
8.0
—
—
—
—
—
Iowa
9.9
1875
740
175
5795
39
Idaho
19.3
2150
1050
171
5465
49
Montana
37.8
2682
1091
204
6386
41
California
54.4
2855
917
182
6379
32
Total area
145
Mean
2206
838
178
5967
38
deep (top 0.9 m Soil) eC
a
(mS/m)
Mean
Std
Min
Max
Cv(%)
New Hampshire
7.5
36.3
15.7
0.5
99.3
43
Triangle
7.6
23.1
8.7
3.9
54.4
38
Illinois
8.0
50.6
21.0
2.5
123.4
42
Iowa
9.9
43.2
20.6
0.4
108.0
48
Idaho
19.3
34.3
20.9
0.4
123.4
61
Montana
37.8
22.7
12.8
0.4
82.8
56
California
54.4
38.0
17.7
0.7
299.6
47
Total area
145
Mean
34.8
19.4
0.4
299.6
56
Notes:
Std, standard deviation; Min, minimum; Max, maximum; CV, coefficient
of variation; N, number of observations.
