Carbon Sink Capacity and Agronomic Productivity of Soils of Semiarid Regions of India - Principles of Sustainable Soil Management in Agroecosystems - page 468

4
3.5
3
2.5
2
1.5
1
0.5

y = -0.0208 x + 1.1985
R 2 = 0.27

0

0 20 40 60

Te mperature (°C)

80 100 120

FIGURE 16.17 Relationship between critical C input requirement and mean temperature of
the location in seven long-term experiments.

A positive relationship has been observed between temperature and critical C input
requirement (Figure 16.17). Information regarding the critical C input requirement
for maintaining the SOC stock of the location at antecedent levels is strategically
very important in terms of C sequestration, soil quality management, and overall
food security in semiarid regions (Lal 2004; Mandal et al. 2007).

16.14 CONCLUSIONS
Poor soil quality with multiple nutrient deficiencies, low NUE, and declining PFP
are among the major concerns in semiarid and rainfed agriculture. The SOC stock
plays a crucial role in the soil's quality, availability of plant nutrients, environmental
functions, and global carbon cycle. Drylands are generally low in fertility and low in
organic matter and hence have a high carbon sink capacity. Carbon storage in the soil
profile not only improves fertility but also abates global warming. Several soil, pro-
duction, and management factors influence carbon sequestration, and it is important
to identify production and management factors that enhance carbon sequestrations
in dryland soils. SOC stocks in the soil profiles across the country show wide varia-
tions and follow the order Vertisols > Inceptisols > Alfisols > Aridisols. Inorganic
carbon and TCSs are larger in Vertisols than in other soil types. SOC stocks decrease
with depth in the profile, while inorganic carbon stocks increase with depth. Among
the production systems, soybean-, maize-, and groundnut-based systems maintain
higher organic carbon stocks than other production systems. Data from experiments
involving long-term cropping, fertilization, and manuring show that mineral fertilizer
application alone can neither sustain the productivity nor maintain the SOC stock. A
strong depletion of carbon occurs irrespective of production systems and soil type.
Application of organics along with mineral fertilizer can sustain productivity and
sequester a significant amount of soil carbon. Depletion of SOC can range from 0.15
Mg C ha -1 year -1 in rice-based systems to 0.92 Mg C ha -1 year -1 in groundnut-fin-
ger millet system. To arrest this depletion, C input of 1.10-3.47 Mg C ha -1 year -1 is
required as a maintenance dose. Further potential of tropical soils to sequester more C
in soil can be harnessed by identifying appropriate production systems and manage-
ment practices for sustainable development and improved livelihoods in the tropics.