Agriculture Reference
In-Depth Information
TABLE 16.22
Relationships of C Input, C Buildup, Profile SOC, and C
Sequestration with SYI in a 21-Year Long-Term Experiment
Parameters
Regression Equation
(
R
2
)
Annual CR C input (
X
)
SYI (
Y
)
Y
rice
= 0.09
X
** + 0.07
0.99
Y
lentil
= 0.14
X
** - 0.03
0.97
Total cumulative C input (
X
)
Y
rice
= 0.001
X
* + 0.18
0.62
Y
lentil
= 0.001
X
* + 0.13
0.68
C buildup % (
X
)
Y
rice
= 0.002
X
* + 0.20
0.65
Y
lentil
= 0.003
X
* + 0.16
0.69
Profile SOC (
X
)
Y
rice
= 0.01
X
* + 0.04
0.65
Y
lentil
= 0.01
X
* - 0.09
0.69
C sequestrated (
X
)
Y
rice
= 0.01
X
* + 0.22
0.65
Y
lentil
= 0.02
X
* + 0.19
0.69
Source:
Srinivasarao, Ch. et al.,
Soil Sci Soc Am J
,
76(1), 168-178, 2012.
Note:
* and ** indicate significance at
P
< 0.05 and 0.01 levels, respectively.
16.13.2.6 Rice-Based Production System
A significant relationship has been observed between SYI and the annual input of
CR C (
R
2
= 0.97-0.99*,
P
< 0.01), total cumulative C input (
R
2
= 0.63-0.68*,
P
<
0.05), C restored (
R
2
= 0.65-0.69*,
P
< 0.05), profile SOC stock (
R
2
= 0.65-0.69*,
P
<
0.05), and total SOC sequestrated (
R
2
= 0.65-0.69*,
P
< 0.05) (Table 16.22).
16.13.3 M
iniMal
c
aRBon
i
npUt
R
eqUiReMentS
foR
a
RReSting
c
aRBon
d
epletion
Long-term cropping without using any organic amendment and/or mineral fertil-
izers causes depletion of the SOC stock. This depletion ranges from 0.15 Mg C ha
-1
year
-1
in rice-based systems to 0.92 Mg C ha
-1
year
-1
in groundnut-finger millet
systems (
Table 16.23
). The highest rate of depletion observed in groundnut-finger
millet systems was 0.92 Mg C ha
-1
year
-1
in semiarid Alfisols, followed by 0.67 Mg
C ha
-1
year
-1
in pearl millet-based systems in Entisols and 0.47 Mg C ha
-1
year
-1
in
soybean-based system in Vertisols. The SOC depletion has been the least in rice-
based systems. There is a negative relationship between mean annual C inputs and
mean SOC depletion rate across locations, soil types, and production systems (
Figure
16.15
). However, rainfall plays a significant role in SOC depletion. Thus, a reciprocal
relationship is expected between rainfall and SOC depletion rate (
Figure 16.16
). In
a similar study, the SOC sequestration potential [C sequestration potential (CSP)],
defined as the rate of increase in the SOC stock over the antecedent stock in the 0-
to 0.2-m depth, ranged from -0.178 Mg C ha
-1
year
-1
(unfertilized control) to 0.572
Mg C ha
-1
year
-1
(50% RDF + 4 Mg groundnut shells per hectare) (Bhattacharyya et
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