2. Soil carbon
Maintenance of soil organic matter is a problem because its native or added forms
are highly unstable
Low level of soil organic carbon in Indian soils
High temperature : Tropical climate
Soil degradation
3. Soil carbon
Soil orders in India :
Vertisol, Inceptisol, Alfisol
SOC stocks ( 0-30 cm depth)
Soil quality improvement through soil C management
Long Term Fertilizer Experiments
Balanced use of NPK fertilizers sustain SOC levels
4. Kyoto protocol
International treaty adopted in December 1997
Aimed to reduce the emission of gases that contribute to global warming
5. Kyoto protocol
As per the Kyoto protocol, agricultural soils has potential to capture and retain
CO2
6. Mineralization of SOC
Active Carbon pool
Microbial carbon
Water extractable carbon
Soluble carbohydrate
Exocellular enzyme
Turn over time : 1-5 years
7. Mineralization of SOC
Slow carbon pool
Humic acid
Fulvic acid
Particulate Organic matter
(coarse fraction organic matter of
size 0.053 mm and 2 mm )
Turn over time : 200-1500 years
8. Sustaining SOC in rice soils
Lowland rice cultivation : submerged soil ecosystem
Anaerobic condition
Decomposition of organic matter is very slow
9. Sustaining SOC in rice soils
Depends on e - acceptors Fe 3+ / SO4
2-
11-20% more C sequestration in continuously cropped wetland rice soils than
maize-rice crop rotation
10. Sustaining SOC in rice soils
Increase in active C pool with advancement in crop growth was observed.
11. Bio-fertilizer component
Enhance soil carbon status through algal photosynthesis
In addition to BNF, sustain SOC levels in rice soils
12. • Both free-living as well as symbiotic
• A composite culture of BGA : Nostoc,
Anabaena, Aulosira
• Soil application :
10 kg ha-1 (Flakes)
BNF : 20-30 kg N/ha
Cyanobacteria : Blue green algae
13. Azolla
Azolla is a free-floating water fern that floats in water
Fixes atmospheric nitrogen in association with nitrogen fixing blue green
alga Anabaena azollae
BNF : 40-60 kg N/ha per rice crop
14. Rice soil : SOC
Sesbania aculeata : organic source
Azolla microphylla : Bio-fertilizer
Enhanced active forms of C
( Water soluble C, microbial biomass C )
Sustain SOC level in rice soil :
Sesbania aculeata + Azolla microphylla
15. Elevated CO2
Rice response to climate change vary with region and cultivar
Atmospheric CO2 concentration is expected to rise from 370 µ mol mol-1
(current level)
16. Open top chamber
Pot experiments : Open top chamber
At elevated CO2 concentration
550 µ mol mol-1 ; 750 µ mol mol-1
Compared with atmospheric CO2 conc.
Carbon dioxide has higher density than air
17. Elevated CO2
CO2 levels
(µ mol mol-1 )
Grain yield
(g pot-1)
Microbial
biomass C
(µg kg-1)
DHA
(µg TPF g-1 day -1 )
370 52.7 424 28.00
550 70.9 562 33.07
750 91.0 714 35.09
CD(P:0.05%) 23.4** 12** 3.0**
18. Elevated CO2
Elevated CO2 levels enhanced growth and yield of rice
Soil microbial mass C was higher at elevated CO2 level
Stimulation of soil enzyme activity at elevated CO2 level
19. Coastal saline soil
CO2 emission : limited on saline soils
Low biological productivity of saline sites limits C inputs to the soil
This limits microbial activity
Low availability of decomposable C as a substrate for microorganisms
20. Cropping sequence
Field experiments were conducted with cotton - maize - sunflower cropping
sequence
Black sandy clay loam soil belonging to montmorillionitic, isohypothermic, Vertic
Ustropept
21. Cropping sequence
The organic carbon build up in soil under intensive cropping system over a
period of five years was evaluated.
Organics (crop residues, composted poultry manure)
22. Cropping sequence
CO2-C evolved during the decomposition of crop residues was higher and faster
Soil carbon depletion was more in the plots incorporated with crop residues
Incorporation of composted poultry manure recorded the maximum soil carbon
build up and microbial biomass.
23. Long term fertilizer experiments (LTFE)
LTFE : Since 1972
Cropping sequence : Finger millet –Maize
Soil : Calcareous medium black sandy clay loam
( Vertic Ustropept)
Inorganic : NPK
Finger millet : 90:45:17.5 kg N,P,K ha-1
Maize : 135:67.5:35 kg N,P,K ha-1
Organic : FYM @ 10 t ha-1
24. SOC forms
After 32 years , in 2004
Water soluble carbon, water soluble carbohydrates increased after maize
Due to photosynthetic efficiency of maize (C4 plant)
Organic carbon in different aggregate size fraction
Highest SOC : 0.25 mm aggregate
Rhizo-deposition of maize
HA > FA
HA,FA : increased with increase in fertilizer application (100 % NPK+FYM )
25. SOC - Land use system
SOC in horticultural system was the highest
Soil : Not exposed to wind / water erosion
Reduced ploughing
SOC in Rice soil was enhanced
Due to anaerobic environment, decomposition of SOC is low
26. Management to improve C sequestration
In high rainfall and hilly areas, impact of erosion on SOC was more
C can be conserved by modifying land configuration or by creating vegetation
barriers to control soil erosion
Addition of crop residues / manures
Legumes , grasses in rotation with food crops enhance SOC
Agro-forestry systems can be practiced
