Carbon Sink Capacity and Agronomic Productivity of Soils of Semiarid Regions of India - Principles of Sustainable Soil Management in Agroecosystems - page 443

120
100
80
60
40
20

0

0 10 20 30

[C mol (+) kg -1 ]

40 50 60 70

FIGURE 16.11 Relationship between CEC and organic carbon stocks in soils ( r = 0.81
[highly significant at P ≤ 0.01 level]). (From Srinivasarao, Ch. et al., Carbon sequestration
strategies under rainfed production systems of India, Central Research Institute for Dryland
Agriculture, Hyderabad (ICAR), India, 2009.)

120
100
80
60
40

20

0

0 10 20 30 40 50 60 70 80

Clay (%)

FIGURE 16.12 Relationship between clay and organic carbon stocks in soils ( r = 0.35 NS [NS
means nonsignificant]). (From Srinivasarao, Ch. et al., Carbon sequestration strategies under
rainfed production systems of India, Central Research Institute for Dryland Agriculture,
Hyderabad (ICAR), India, 2009.)

16.8 REASONS FOR SOIL CARBON DEPLETION
IN RAINFED TROPICAL SYSTEMS
India, similar to China and other countries, is facing a dual challenge of reducing
CO 2 emissions and enhancing the gross domestic product (GDP) by 20% to 25% by
2020 compared with the 2005 baseline. In this context, the importance of sustainable
management of soils of agroecosystems to enhance SOC stocks by sequestering atmo-
spheric CO 2 cannot be overemphasized. Both the magnitude and quality of SOC stock
are critical to improving soil quality, increasing crop productivity, and offsetting CO 2
emissions (Lal 2004; Smith 2007). Optimum levels of SOC can be managed through
the adoption of RMPs such as appropriate crop rotations (Wright and Hons 2005), soil
fertility management, using inorganic fertilizers and organic amendments (Schuman
et al. 2002; Mandal et al. 2007; Majumder et al. 2008), and use of conservation tillage
methods (Lal 2009). In rainfall-scarce environments of tropical and subtropical regions
characterized by arid and semiarid climates, soils are inherently low in SOC stock, and