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H. Elbasiouny and F. Elbehiry
Briefly, carbon sequestration is defined as the storage of carbon in long-term terrestrial or aquatic C stocks, resulting in reducing the atmospheric CO 2 concentration
[15]. It is reported [23] that stabilization of soil organic matter (SOM), thus, soil C
sequestration can occur through important biochemical and physical mechanisms.
Biochemical processes include interactions of recalcitrant litter that slow or inhibit
microbial degradation, and chemical conversions through humification and other
oxidative reactions that lead to the synthesis of new more resistant compounds to
decay than their precursors. Conceptual models of SOC define three protection mechanisms: (i) silt + clay protected SOC (i.e. mineral particles <53 µm), (ii) microaggregate protected SOC (i.e. 53–250 µm), and (iii) biochemically protected SOM
because of its chemical composition and through chemical complexing processes.
Also, a fourth SOC stock is defined as the unprotected carbon (C), which is comprised
in part of particulate organic matter (POM) [24]. Thus; soil sequesters C through some
processes such as humification of OM, the formation of organo-mineral aggregates,
incorporation of OM in a subsurface layer beneath the plow zone, the addition of
deep root residues and precipitation of carbonates as SIC [18]. It is reported that in
photosynthesis, plants utilize atmospheric CO 2 , and store organic C above and below
ground biomass. Therefore, using growing plants is an important mean not only to
remove CO 2 from the atmosphere but also to convert atmospheric CO 2 to usable
food, fiber, and excess biomass, and improve the conversion of the excess biomass to
SOC. Although field studies have long documented the ability of plants to transport
C from the atmosphere to the soil, national inventories that quantify the amount of
C being stored are relatively new but necessary for any type of full C accounting
system [8].
4 Soil C Stock
4.1 Soil Organic C Stock
The SOC plays a fundamental role in improving soil quality, sustaining, and improving crop productivity and providing other ecosystem services, such as enhanced soil
structure and water retention. As well it plays a very important role in mitigating
global warming through reducing the net atmospheric CO 2 [25–28]. The SOC is the
largest terrestrial C stock with a global estimate of 2344 Gt, stored in the top 3-m soil
layer and 1115–2200 Pg in a meter soil profile [11, 16, 29, 30], it contains approximately twice as much as carbon in the atmosphere [31]. The global SOC stock in
the top 1 m is approximately 1500 Pg (1 Pg = 1 Gt = 10
15 g) C. Agro-ecosystems,
representing 10% of the total terrestrial area, are amongst the most vulnerable ecosystems to the global climate change impacts because of their large carbon stock. Small
changes in SOC stock may have considerable effects on the carbon dioxide concentration in the atmospheric [29, 30]. Moreover, it has been reported that a 1%
H. Elbasiouny and F. Elbehiry
Briefly, carbon sequestration is defined as the storage of carbon in long-term terrestrial or aquatic C stocks, resulting in reducing the atmospheric CO 2 concentration
[15]. It is reported [23] that stabilization of soil organic matter (SOM), thus, soil C
sequestration can occur through important biochemical and physical mechanisms.
Biochemical processes include interactions of recalcitrant litter that slow or inhibit
microbial degradation, and chemical conversions through humification and other
oxidative reactions that lead to the synthesis of new more resistant compounds to
decay than their precursors. Conceptual models of SOC define three protection mechanisms: (i) silt + clay protected SOC (i.e. mineral particles <53 µm), (ii) microaggregate protected SOC (i.e. 53–250 µm), and (iii) biochemically protected SOM
because of its chemical composition and through chemical complexing processes.
Also, a fourth SOC stock is defined as the unprotected carbon (C), which is comprised
in part of particulate organic matter (POM) [24]. Thus; soil sequesters C through some
processes such as humification of OM, the formation of organo-mineral aggregates,
incorporation of OM in a subsurface layer beneath the plow zone, the addition of
deep root residues and precipitation of carbonates as SIC [18]. It is reported that in
photosynthesis, plants utilize atmospheric CO 2 , and store organic C above and below
ground biomass. Therefore, using growing plants is an important mean not only to
remove CO 2 from the atmosphere but also to convert atmospheric CO 2 to usable
food, fiber, and excess biomass, and improve the conversion of the excess biomass to
SOC. Although field studies have long documented the ability of plants to transport
C from the atmosphere to the soil, national inventories that quantify the amount of
C being stored are relatively new but necessary for any type of full C accounting
system [8].
4 Soil C Stock
4.1 Soil Organic C Stock
The SOC plays a fundamental role in improving soil quality, sustaining, and improving crop productivity and providing other ecosystem services, such as enhanced soil
structure and water retention. As well it plays a very important role in mitigating
global warming through reducing the net atmospheric CO 2 [25–28]. The SOC is the
largest terrestrial C stock with a global estimate of 2344 Gt, stored in the top 3-m soil
layer and 1115–2200 Pg in a meter soil profile [11, 16, 29, 30], it contains approximately twice as much as carbon in the atmosphere [31]. The global SOC stock in
the top 1 m is approximately 1500 Pg (1 Pg = 1 Gt = 10
15 g) C. Agro-ecosystems,
representing 10% of the total terrestrial area, are amongst the most vulnerable ecosystems to the global climate change impacts because of their large carbon stock. Small
changes in SOC stock may have considerable effects on the carbon dioxide concentration in the atmospheric [29, 30]. Moreover, it has been reported that a 1%