Agriculture Reference
In-Depth Information
Table 9.6
Whole-Soil %C and %N, pH, and Extractable P (ppm) for Baseline,
2000, and 2004 Soils
Whole-soil
%C
Whole-soil
%N
Extractable P
(ppm)
pH
Baseline
Average
5.76
1.20
0.091
13.90
By landscape
Dambo
5.68
1.60
0.122
2.60
Dambo margin
5.83
0.90
0.067
12.37
Hillside
5.78
0.97
0.076
26.73
D1
Cropping system
MZ+F
5.83
1.13
0.079
13.21
MZ-F
5.71
1.20
0.089
13.70
SS-F
5.74
1.18
0.087
12.00
TV-F
5.61
0.87
0.063
14.03
PP-F
5.70
1.22
0.086
19.68
By landscape
Dambo
5.73
1.29
ab
0.095
1.89
a
Dambo margin
5.64
0.91
a
0.068
13.31
b
Hillside
5.78
1.23
b
0.083
28.38
b
D2
MZ+F
5.60
1.01
0.076
26.71
MZ-F
5.80
1.00
0.071
19.85
SS+1/2F
5.52
1.11
0.083
27.64
TV+1/2F
5.49
1.14
0.084
21.46
PP+1/2F
5.64
0.98
0.073
23.73
By landscape
Dambo
5.49
1.29
0.085
5.16
a
Dambo margin
5.58
0.90
0.068
15.64
a
Hillside
5.76
1.13
0.082
50.55
b
Note:
Lowercase letters indicate significant differences based on one-way ANOVAs
(
P
< 0.05 Tukey's post hoc test).
in soil percentage C. Even without changes in total percentage C or percentage N, it is
possible that changes in more labile fractions of SOM may have occurred as discussed
previously. We attempted to isolate the more labile light fraction of the SOM using a size
density fractionation method (Meijboom et al., 1995; Barrios et al., 1996) but were unable to
isolate sufficient quantities of soil from the initial size fractionation to complete the density
fractionation, despite using the recommended 500 g of soil.
Some studies have shown benefits of legume incorporation on soil P availability due to
increased mineralization of organic P (Randhawa et al., 2005) or solubilization of inorganic
P fixed by Fe and Al in the soil (Mweta et al., 2007). Here, no legume effects on available
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