Soil organic matter plays an important role in carbon sequestration. Agricultural soils are among the largest reservoirs of carbon, estimated to be able to sequester 20 petagrams of carbon in 25 years. Soils contain about three times as much carbon as vegetation and twice as much as the atmosphere. Carbon storage in soils depends on the balance between input of dead plant material and losses from decomposition; management practices that increase soil organic matter like no-till farming can sequester more carbon in biomass and soils. Doing so provides benefits like increased soil fertility and productivity while helping mitigate climate change. However, carbon sequestration through soil is reversible if agricultural practices or disasters cause stored carbon to re-enter the atmosphere

1. Importance of Soil Organic Matter in Carbon Sequestration
Jan Van Wambeke Jan.VanWambeke@fao.org
Pilar Román Pilar.Roman@fao.org

2. FAO is concerned with the effect of agriculture on climate
change, the impact of climate change on agriculture and with
the role that agriculture can play in mitigating climate change.
Historically, land-use conversion and soil cultivation have been
an important source of greenhouse gases to the atmosphere. It
is estimated that they are responsible for about 30% of GHG
emissions

3. The challenges for agriculture
HIGHER AND DIVERSIFIED FOOD CONSUMPTION
WATER
SUSTAINABILITY FOR
FUTURE
GENERATIONS
LAND
CLIMATE
CHANGE
Irregular water availability,
extreme weather events,
higher normal temperatures
GENETIC RESOURCES
GROWING WORLD POPULATION
3

4. Carbon sequestration: the process of removing carbon from the atmosphere
or preventing its release altogether by guarding it in a reservoir.
Agricultural soils are among the planet’s largest reservoirs of carbon. It is
estimated that soils can sequester around 20 Pg C in 25 years, more than 10 %
of the anthropogenic emissions
Source: CGIAR

5. The quantity of carbon stored in soils is highly significant; soils contain about 3
times more carbon than vegetation and twice as much as that which is present in
the atmosphere
Source: FAO
Carbon storage in soils is the balance between the input of dead plant material
(leaf and root litter) and losses from decomposition and mineralization processes
(heterotrophic respiration).
Under aerobic conditions, most of the carbon entering the soil is labile, and
therefore respired back to the atmosphere through the process known as soil
respiration or soil CO2 efflux.

6. “The importance of these activities is that any action taken to sequester carbon in
biomass and soils will generally increase the organic matter content of soils, which
in turn will have a positive impact on environmental, agricultural and biodiversity
aspects of ecosystems.
The consequences of an increase in soil carbon storage can include increases in soil
fertility, land productivity for food production and security, and prevention of land
degradation”
Source: FAO

7. Soil carbon sequestration presents both advantages and disadvantages as a
means of mitigating climate change.
•Advantages
– Relatively low-cost
– It can be readily implemented
– it provides multiple associated benefits as the resultant increase in root
biomass and soil organic matter enhances water and nutrient retention,
availability and plant uptake and hence land productivity
•Disadvantages
– It is reversible, changes in agricultural management practices or disasters as
fires, droughts or pests can accelerate or reverse the degree of sequestration
in a relatively short time frame.

8. FAO material on
Carbon
Sequestration