Agriculture Reference
In-Depth Information
where the SOC concentration is in g kg
−1
and soil bulk density (SBD) is in Mg m
−3
.
The change in SOC pool in treatments was computed with reference to the control
(CK) by using Equation 7.2:
ΔSOC (Mg ha
−1
) = Tr (Mg ha
−1
) − CK (Mg ha
−1
)
(7.2)
where ΔSOC is the change in SOC pool under a specific treatment (Tr) in compari-
son with that under CK. The maximum rate (MR) and average rate (AR) of SOC
change were calculated using Equations 7.3 and 7.4:
AR = (kg ha
−1
year
−1
) = (SOC
f
− SOC
i
)/
t
(7.3)
MR = (kg ha
−1
year
−1
) = (SOC
m
− SOC
i
)/
t
(7.4)
where SOC
i
is SOC pool at the beginning of the experiment and SOC
f
is the final
SOC pool after
t
years of experiment, and SOC
m
is the maximum SOC pool during
the experimental period.
7.2.4 d
AtA
p
rOCeSSing
And
S
tAtiStiCS
Data were organized into CK, O, CF, UF, CFO, and UFO fertilizers and manage-
ment treatments among the eight different sites. The SOC pools for different treat-
ments were computed into mean and standard deviation (
x
±sd
), and the SOC pool
trend line for different treatments was computed using Microsoft Excel 2007. The
significance of differences at
P
< 0.05 and
P
< 0.01 between fertilizers and manage-
ment in different long-term experiment sites were tested using SPSS (version 13.0).
7.3
RESULTS AND DISCUSSIONS
7.3.1 SOC p
OOl
C
hAnge
under
d
ifferent
f
fertilizer
m
AnAgementS
ACrOSS
hhh
The mean SOC pool in 0-20 cm depth was 18.9 ± 1.8, 19.7 ± 1.7, 20.8 ± 2.1, 20.3 ±
2.5, 23.4 ± 7.2, and 24.3 ± 6.6 Mg ha
−1
for CK, UF, CF, O, UFO, and CFO fertilizer
management treatments, respectively (Table 7.4). The numbers of observations (
n
) for
different treatments were 204 for CF, 107 for O, 172 for UF, 282 for CFO, 238 for UFO,
and 110 for CK. The SOC pool for all fertilizer and managements differed significantly
from that of CK, and that for CF, UF, and O from those of CFO and UFO fertilizer
and managements. The maximum SOC pool was observed for the CFO, and the least
for the CK. The SOC pool was in the order of CFO > UFO > O > CF > UF > CK.
The changes in SOC pool for diverse fertilizer managements can be organized
into three groups. First is the baseline SOC pool for CK in arable land without any
fertilizer input. Second is the high SOC pool for CFO and UFO treatments with
combined use of organic manure and chemical fertilizer. Third is the middle range
of SOC pool for UF, CF, and O fertilizer managements. The SOC pool in fertilizer
managements with a middle range can be increased to those of the CFO and UFO
levels with the adoption of improved management.
