Carbon Sink Capacity and Agronomic Productivity of Soils of Semiarid Regions of India - Principles of Sustainable Soil Management in Agroecosystems - page 446

Principal reservoirs of C (Pg) are the following (Kimble et al. 1990): oceans =
39,000; soils (worldwide) = 1576; atmosphere = 800; tropical soils = 506, and soil
litter = 3. The oceanic pool is the largest, followed by the geologic, pedologic (soil),
biotic, and atmospheric pools (Lal 2004). All these pools are interconnected, and
C circulates among them. The pedologic or soil C pool comprises SOC and SIC
components. The SIC stock is especially important in soils of dry regions. The SOC
concentration ranges from low in soils of the arid regions to high in soils of the tem-
perate regions and extremely high in organic/peat soils (Eswaran et al. 2000).
16.10 CARBON MANAGEMENT OPTIONS
The SOM is the storehouse of many plant nutrients, and it strongly influences the
biological activity and productive capacity of soils. Over the years, efforts have
been made to improve SOM status in continuously cropped soils by fertilization,
manuring, and residue management practices. However, maintaining and increasing
SOM is a major challenge in dryland soils due to high temperature and moisture
stress. A study of 21 locations across rainfed regions of India covering eight produc-
tion systems revealed that most soils are low in SOC and available N, and low to
high in available P, K, and S. Many soils are deficient in available Mg, Zn, and B
(Srinivasarao et al. 2006, 2008a,b). Therefore, crop and soil management practices
have to be adapted to ensure long-term crop/cropping systems. Application of plant
nutrients (Paustian et al. 1997) and organic amendments and inclusion/cultivation of
legumes favor improvement of soil fertility and sustainability. This is directly related
to maintaining the quantity of SOM, which is a critical component of soil productiv-
ity. However, resource-poor farmers in dryland regions apply a meager quantity of
nutrients, and thus, crops suffer from multinutrient deficiencies (Srinivasarao et al.
2003). The best option seems to be an integrating farm-generated organic manure
with inorganic fertilizers to enhance SOM, improving productivity and advancing
sustainability of dryland agriculture. Crop rotation, residue management, and fertil-
ization can maintain the level of SOM (Campbell et al. 1991). Ali et al. ( 2002) stated
that by improving physical, chemical, and biological properties of soils, food legume
cultivation could arrest the declining trend in productivity of cereal-cereal systems.
The availability of CR is a major problem in India due to its competing uses. In some
crops, by-products (e.g., groundnut shells) are available for soil application, as they
do not have major alternate uses. Though chemical fertilization has a demonstrable
and great effect on crop yields, poor farmers in rainfed regions mostly rely on farm-
yard manure (FYM) and other organic manures because of the high cost of chemical
fertilizers. Thus, nutrient management and residue incorporation can make a major
contribution to soil C sequestration.
16.10.1 S ite -S pecific RMp S
Adoption of RMPs can enhance the rate of SOC sequestration (Lal 2004), thereby
sequestering atmospheric CO 2 and mitigating climate change. West and Post
(2002) observed that conversion from conventional tillage (CT) to no-till (NT) can
sequester 57 ± 14 g C m −2 year −1 , excluding wheat ( Triticum aestivum L.) -fa l low