Carbon Sink Capacity and Agronomic Productivity of Soils of Semiarid Regions of India - Principles of Sustainable Soil Management in Agroecosystems - page 439

300

Organic carbon (Mg/ha)
Inorganic carbon (Mg/ha)
To tal carbon (Mg/ha)

250

200

150

100

50

0

Inceptisols (6) Alfisols/Oxisols (4) Vertisols (9) Aridisols (2)

FIGURE 16.7 Carbon stocks in diverse soil types under rainfed systems. (From Srinivasarao,
Ch. et al., Carbon sequestration strategies under rainfed production systems of India, Central
Research Institute for Dryland Agriculture, Hyderabad (ICAR), India, 2009. Srinivasarao,
Ch. et al., Comm Soil Sci Plant Anal , 40(15), 2338-2356, 2009.)

to 59.7 with a mean of 43.7 in Inceptisols, 23.3 to 49.8 with a mean of 30.8 in Alfisols,
28.6 to 95.9 with a mean of 46.4 in Vertisols, and 20.1 to 27.4 with a mean of 23.7 in
Aridisols. The stabilizing effect of clay particles on SOC in aggregation decreases
in the following sequence: allophone > amorphous minerals > smectite > illite >
kaolinite (Van Breemen and Feijtel 1990). In arid and semiarid regions, Vertisols
with smectite as a dominant mineral have larger SOC stocks than illitic Inceptisols
and kaolinitic Alfisols.
Similar to SOC, the SIC concentration also varies widely among the soil types.
Vertisols contain larger SIC, followed by Inceptisols, Alfisols, and Aridisols. The
SIC stocks (Mg ha -1 ) range from 22.3 to 135.1 (mean of 69.1) in Inceptisols, 8.8 to
57.0 (mean of 26.8) in Alfisols, 16.0 to 367.6 (mean of 178.1) in Vertisols, and 14.3
to 20.5 (mean of 17.4) in Aridisols. In most cases, surface soil storage of SOC is
greater than in subsoil layers, while the reverse is the trend in the case of SIC. TCSs
(Mg ha -1 ) range from 52.1 to 192.1 (mean of 112.8) in Inceptisols, 32.1 to 82.4 (mean
of 57.6) in Alfisols, 44.7 to 396.2 (mean of 224.5) in Vertisols, and 34.4 to 47.9
(mean of 41.1) in Aridisols. The TCS is also greater in Vertisols, followed by that in
Inceptisols, Alfisols, and Aridisols.
The SOC concentration and stock depend on climate, soil type, and land use
(Dalal and Mayer 1986). Wani et al. (2003) reported an increase in C sequestration
in Vertisols by adopting RMPs (32 kg SOC ha -1 year -1 ) in pigeon pea-based sys-
tems as compared to sorghum-based systems under on-farm management. The SOC
concentrations reported are lower in soils of tropical regions in India than those of
Australia (Dalal and Mayer 1986; Dalal 1989; Murphy et al. 2002; Young et al. 2005).
Significantly lower concentrations of SOC in these soils are attributed to high rates
of oxidation of SOM due to prevailing high temperatures and frequent cultivation
(Dalal and Chan 2001; Wani et al. 2003). Young et al. (2005) reported that Vertisols
with high clay content contain higher SOC stocks than other soils with lower clay
contents. Sahrawat (2003) reported that calcium carbonate is a common mineral
in soils of the dry regions of the world, stretching from subhumid to arid zones,