Agriculture Reference
In-Depth Information
Table 3.7.1.
Measured soil organic matter content and dispersion ratios, and estimated
'stabilized' organic matter contents.
Cropping
1961-1996
Cropping
1996
Initial
OM (%)
1996
OM (%)
OM
change (%)
'Stabilized'
OM (%)
Dispersion
ratio (
SEM
)
Site
A
Arable
Calabrese
a
6.4
a
3.5
−
2.9
***
2.5
8.6 (0.24)
a
5.3
a
B
Arable
Cauliflower
3.0
−
2.3
***
3.3
6.0 (0.44)
C
Arable
Winter wheat
a
2.2
a
2.3
+0.1
2.2
7.8 (0.51)
E
Ley-arable
Ley
2.4
2.7
+0.3
2.6
8.2 (0.12)
F
Ley-arable
Ley
3.1
3.1
0
3.3
5.8 (0.11)
G
Arable
Cauliflower
3.0
2.5
−
0.5
***
2.6
8.0 (0.60)
H
Arable
Cauliflower
5.2
3.6
−
1.7
**
*
3.3
7.7 (0.17)
I
Ley-arable
Peas
3.4
3.1
−
0.3
*
3.1
8.0 (0.57)
J
Ley-arable
Peas
3.5
3.1
−
0.4
*
3.2
7.0 (0.20)
K
Arable
Winter wheat
2.6
2.5
−
0.1
*
2.8
8.7 (0.32)
L
Arable
Winter wheat
4.4
3.9
−
0.5
***
3.4
7.1 (0.33)
M
Ley-arable
Ley
2.6
2.7
+0.1
2.8
6.9 (0.34)
N
Ley-arable
Ley
4.3
4.0
−
0.3
*
3.9
3.1 (0.43)
a
Measured in 1964, all other initial figures measured in 1969.
SEM
= standard error of the mean.
**
P< 0.01;
***
P< 0.001
Sites A and B were in permanent pasture until the early 1960s
(ploughed out in 1963 and 1962, respectively) and showed an exponential
decline in soil organic matter content. The initial rate of decline was similar
for both sites. However, both sites appear to be at or approaching
'stabilized' soil organic matter levels of ~2.5 and ~3.3%, respectively. The
topsoil at site B was more stable than at site A (dispersion ratios of 6.0 and
8.6, respectively), corresponding to the higher organic matter levels at site
B.
The two initially higher organic matter sites (H and L) showed a
decline in soil organic matter levels over time (
P
< 0.05). The rapid initial
decline at site H suggests that this site may have been ploughed out of
pasture prior to sampling, although this cannot be confirmed with the
available historical land management data. The 'stabilized' organic matter
levels were estimated at 3.3 and 3.4% for sites H and L, respectively, with
the sites having similar structural stabilities. Site G showed a slow decrease
in soil organic matter content (
P
< 0.05) and sites C and K no change
(
P
> 0.05). It is interesting to note the 'apparent' decreases in the early
1980s at sites G and L which may be due to deeper ploughing, diluting
topsoil organic matter levels.
The ley-arable sites showed no changes (
P
> 0.05) in soil organic
matter content over time. 'Stabilized' organic matter values were estimated
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