Agriculture Reference
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350
Organic carbon (Mg ha
-1
)
Inorganic carbon (Mg ha
-1
)
To tal carbon (Mg ha
-1
)
300
250
200
150
100
50
0
<550
550-850
850-1000
1000-1100
>1100
Rainfall (mm)
FIGURE 16.9
Soil carbon stocks in rainfed production systems in relation to rainfall. (From
Srinivasarao, Ch. et al., Carbon sequestration strategies under rainfed production systems of
India, Central Research Institute for Dryland Agriculture, Hyderabad (ICAR), India, 2009.)
18
16
14
12
10
8
6
4
2
0
300
500
700
900
Rainfall (mm)
1100
1300
1500
FIGURE 16.10
Relationship between mean annual rainfall (mm) and SOC in surface layer
(0-15 cm) under rainfed conditions (OC stock = 1.91 + 0.008x,
r
= 59 [significant at
P
≤ 0.05
level]). (From Srinivasarao, Ch. et al., Carbon sequestration strategies under rainfed produc-
tion systems of India, Central Research Institute for Dryland Agriculture, Hyderabad (ICAR),
India, 2009.)
[significant at
P
≤ 0.01 level]) (
Fig u re 16.11
), while clay content is only slightly cor-
related with the SOC stocks (
Figure 16.12
). This trend indirectly indicates that the
specific type of clay mineral with a larger surface area is largely responsible for higher
potential of C sequestration.
It has been postulated that climatic aridity is responsible for the formation of
PIC, and this is a reverse process to the enhancement in SOC stock. Yet, there exists
a strong synergism between increase in SOC and SIC stocks (Sahrawat 2003). The
present scenario of changing climatic parameters (e.g., temperature and annual rain-
fall in some regions of the country) may reduce the potential of C sequestration in
soils of the Indian subcontinent. Therefore, the arid climate will continue to remain
as a bane for Indian agriculture because it will deplete SOC stock but lead to for-
mation of PIC along with the concomitant development of sodicity and/or salinity
(Eswaran et al. 1993; Bhattacharya et al. 2000).
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