Soil Carbon Sequestration for Climate Change Mitigation …
157
increment SOC content of the surface soil (0–20 cm) could increase cereal yield by
430 kg ha
−1 and decline yield variability by 3.5% [27].
Many studies in the last decades have reinforced the role of soil as a C sink,
the importance of SOC in the global C cycle and the potential feedback to climate
change. Hence, scientists worldwide have paid their attention to the potential factors
that may affect the storage of C in the soil. For example, land use and management
systems, the application of crop residues or agro-food industry wastes, temperature
and precipitation, soil properties, landscape position, slope … etc. [26, 27]. Thus,
there is always an urgent need for the adoption of restorative management practices
in agricultural soils for improving the soil fertility and environment.
As well, the shifts in climatic factors such as temperature and precipitation notably
affect the change of SOC because C sequestration in the agriculture soil is a function
of both primary production and decomposition of organic matter (OM), which effect
by these factors [29]. As well, the agricultural SOC stock can be strongly affected
by human activities, such as land use changes, which influence the input of OM and
soil carbon source and alter the soil structure and the equilibrium of OC by changing
the cultivation practice, and ultimately change soil carbon sequestration capacity.
Therefore, changes in such practices as tillage and fertilization along with land use
can directly affect soil physicochemical and microbiological properties and affect
the ability of soil aggregates and OC content [31]. According to different studies
worldwide, there are many management practices can be used for enhancing SOC
such as zero or reduced tillage, mulching and residue management or composting,
application of organic fertilizers and manure, improved rotations, use of improved
crop varieties, and water management [32]. However, others have argued that claims
about the possible benefits of increasing C inputs to the soil must be made carefully
because of the uncertainties regarding the quantity that can be sequestered under
different climates and soil types. Therefore, it is an urgent need to highlight the
relationships between C inputs, SOC sequestration and crop productivity [27].
As well, early detection and prediction of changes in a long-term monitoring of
SOC contents are crucial to achieve an effective management of SOC not only to
minimize SOC loss and reductions in soil fertility, but also to focus on strategies for
soil C sequestration should be focused in the subsoil together with the use of appropriate recommended management practices [32]. However, short- and medium-term
changes in soil total organic C (TOC) are hard to detect due to the high background
C and temporal and spatial variabilities of recalcitrant C [11, 25].
Since SOM is a complex and heterogeneous entity comprising of a continuum
of materials, which have different degrees of stabilization and turnover times, the
response of SOC to land use can be better understood by isolating different fractions
of SOC. The SOC stock can be chemically divided into labile organic C, semi-labile
organic C and recalcitrant organic C. Compared with recalcitrant OC, labile and
semi-labile C stocks have smaller sizes while higher bioavailability with short or
medium-term storage, thus they are more sensitive to environmental changes. Since
the changes in SOC fractions may affect both nutrient supply and soil C sequestration,
it is required to fractionate and quantify those stocks for a better understanding of
the impact of land-use on SOC kinetic [11, 30]. Labile organic C fractions include
157
increment SOC content of the surface soil (0–20 cm) could increase cereal yield by
430 kg ha
−1 and decline yield variability by 3.5% [27].
Many studies in the last decades have reinforced the role of soil as a C sink,
the importance of SOC in the global C cycle and the potential feedback to climate
change. Hence, scientists worldwide have paid their attention to the potential factors
that may affect the storage of C in the soil. For example, land use and management
systems, the application of crop residues or agro-food industry wastes, temperature
and precipitation, soil properties, landscape position, slope … etc. [26, 27]. Thus,
there is always an urgent need for the adoption of restorative management practices
in agricultural soils for improving the soil fertility and environment.
As well, the shifts in climatic factors such as temperature and precipitation notably
affect the change of SOC because C sequestration in the agriculture soil is a function
of both primary production and decomposition of organic matter (OM), which effect
by these factors [29]. As well, the agricultural SOC stock can be strongly affected
by human activities, such as land use changes, which influence the input of OM and
soil carbon source and alter the soil structure and the equilibrium of OC by changing
the cultivation practice, and ultimately change soil carbon sequestration capacity.
Therefore, changes in such practices as tillage and fertilization along with land use
can directly affect soil physicochemical and microbiological properties and affect
the ability of soil aggregates and OC content [31]. According to different studies
worldwide, there are many management practices can be used for enhancing SOC
such as zero or reduced tillage, mulching and residue management or composting,
application of organic fertilizers and manure, improved rotations, use of improved
crop varieties, and water management [32]. However, others have argued that claims
about the possible benefits of increasing C inputs to the soil must be made carefully
because of the uncertainties regarding the quantity that can be sequestered under
different climates and soil types. Therefore, it is an urgent need to highlight the
relationships between C inputs, SOC sequestration and crop productivity [27].
As well, early detection and prediction of changes in a long-term monitoring of
SOC contents are crucial to achieve an effective management of SOC not only to
minimize SOC loss and reductions in soil fertility, but also to focus on strategies for
soil C sequestration should be focused in the subsoil together with the use of appropriate recommended management practices [32]. However, short- and medium-term
changes in soil total organic C (TOC) are hard to detect due to the high background
C and temporal and spatial variabilities of recalcitrant C [11, 25].
Since SOM is a complex and heterogeneous entity comprising of a continuum
of materials, which have different degrees of stabilization and turnover times, the
response of SOC to land use can be better understood by isolating different fractions
of SOC. The SOC stock can be chemically divided into labile organic C, semi-labile
organic C and recalcitrant organic C. Compared with recalcitrant OC, labile and
semi-labile C stocks have smaller sizes while higher bioavailability with short or
medium-term storage, thus they are more sensitive to environmental changes. Since
the changes in SOC fractions may affect both nutrient supply and soil C sequestration,
it is required to fractionate and quantify those stocks for a better understanding of
the impact of land-use on SOC kinetic [11, 30]. Labile organic C fractions include