Geoscience Reference
In-Depth Information
1.2
Cover
No cover
P > 0.05
2000
1.0
*
*
*
*
*
*
0.8
* *
*
*
0.6
0.4
1.2
2001
1.0
*
*
0.8
*
*
*
*
*
0.6
*
*
*
0.4
1.2
2002
1.0
0.8
*
*
*
*
*
*
*
*
*
0.6
0.4
1.2
*
*
*
*
2003
*
*
*
*
1.0
*
* *
*
**
*
0.8
*
*
*
*
0.6
0.4
90
120
50
180
210
240
270
300
Day of Ye ar
fIGURe 19.3
Apparent soil conductivity (EC
a
) for the main treatment of cover and no cover during 2000,
2001, 2002, and 2003.
19.3.2 s
t a t i s t i c a l
a
n a l y s i s
Three primary dynamic quantities in a cornfield are the soil temperature, soil moisture, and nutrient
levels. The EC
a
data for 2000 to 2002 have been corrected to the equivalent temperature of 25°C
(McKenzie et al., 1989). The remaining dynamics of soil moisture and nutrient levels (NO
3
-N being
a primary contributor) are examined in the sections that follow.
19.3.2.1
Main plots—Cover Crop
Cover crop is the main plot of the split-plot design. Survey EC
a
temperature corrected data were col-
lated with all treatments identified and all survey dates concatenated for each year. Soil data were
included in the data file and associated with EC
a
of replicate 2. A standardized estimate was gener-
ated that partitions the percent contribution between the values of soil moisture and NO
3
-N toward
the variability of EC
a
across survey dates; this test was done for temperature-corrected EC
a
data for
2000 to 2003, with results shown in Table 19.1. The results indicated that for the -CC treatments,
