300
H. Elbasiouny and F. Elbehiry
land use or climate, may influence not only long-term ecosystem functions but also
the global atmospheric carbon budget and. Cropland soils contain slightly more than
10% (about 170 Pg C) of the total SOC pool. Therefore, a great attention is paid
to carbon sequestration in agricultural soils [24] because of its potential impact on
global climate change [22]. Subsequently, boosting C sequestration and minimizing
GHG emissions has become one of the essential tasks worldwide to the effective
combat of upcoming climate change. In considering the magnitude of soil C stock,
even small changes in this reservoir can exert a substantial influence on gaseous C
emissions and concentrations of atmospheric CH 4 and CO 2 , thus affecting global
climate change. Under active human interference and cultivation, the soils in paddy
fields usually have a larger potentiality of C sequestration than natural wetland soils
[14].
Respecting soil C stocks, submerged rice ecology has also emerged as a potential
C sink. Very few studies have demonstrated the unique soil C chemistry in rice soils.
Slow decomposition of organic substances is common in rice soils under extended
waterlogging, anaerobic conditions due to depletion of O 2 levels and the absence of
iron oxides and hydroxides as electron acceptors. This leads to higher accumulation
of stable fractions of C or in the other meaning, SOC sequestration in rice systems
[18]. However, under such conditions of submergence and increasing the quantity of
SOM, the degradation of soil quality because of the breakdown of stable aggregates
and deterioration of soil organic matter occurs. Crop rotations are known to favor
the enforcement of SOC and improving soil nutrients comparing to monocultures.
Continuous monoculture will not be active in sequestering C [25]. It is stated that
in the past decades, the SOC declined in high-yielding cropping systems, especially
in rice production systems, due to using chemical fertilizers and pesticides instead
cover crops and organic mature to retain crop growth and to increase grain yields [17].
However, SOC accumulation was attributed to the increased application of chemical
fertilizers that stimulate greater rice yields, higher biomass production, and higher
returning of crop residues to the soil, over the last several decades [23].
Owing to its high accumulation rate of SOC, rice cultivation may play a substantial
role in mitigation CO 2 in the atmosphere [23]. The dynamics of soil carbon (C) and
nitrogen (N) in submerged rice soils are different from those of aerobic, because
of maintaining submerged rice soils at lower redox potentials. Recently, stagnation
or decline in yields has been observed worldwide under the intensive rice-based
cultivation systems; this is attributed to the loss of quality and quantity of SOC
which influenced nutrient supply, specifically N [3]. It is reported that SOC in the
surface layer (0–20 cm) of paddy field is higher than its corresponding in the upland
croplands. They explained that the strong aggregate stability of paddy soil boosts
the SOC conservation and the enrichment of SOC in macro-aggregates, resulting in
a greater carbon sequestration potential in this soil. They also reported a declining
tendency of SOC after paddy conversion into the vegetable field [26].
On the other hand, rice agriculture contributes meaningfully to global straw production. These agricultural residues are spread in the field, removed from the field,
burned in situ, piled, incorporated to the soil, or mulched on the next crop. In the
past, straw was regularly removed from the field and used as fuels or construction
H. Elbasiouny and F. Elbehiry
land use or climate, may influence not only long-term ecosystem functions but also
the global atmospheric carbon budget and. Cropland soils contain slightly more than
10% (about 170 Pg C) of the total SOC pool. Therefore, a great attention is paid
to carbon sequestration in agricultural soils [24] because of its potential impact on
global climate change [22]. Subsequently, boosting C sequestration and minimizing
GHG emissions has become one of the essential tasks worldwide to the effective
combat of upcoming climate change. In considering the magnitude of soil C stock,
even small changes in this reservoir can exert a substantial influence on gaseous C
emissions and concentrations of atmospheric CH 4 and CO 2 , thus affecting global
climate change. Under active human interference and cultivation, the soils in paddy
fields usually have a larger potentiality of C sequestration than natural wetland soils
[14].
Respecting soil C stocks, submerged rice ecology has also emerged as a potential
C sink. Very few studies have demonstrated the unique soil C chemistry in rice soils.
Slow decomposition of organic substances is common in rice soils under extended
waterlogging, anaerobic conditions due to depletion of O 2 levels and the absence of
iron oxides and hydroxides as electron acceptors. This leads to higher accumulation
of stable fractions of C or in the other meaning, SOC sequestration in rice systems
[18]. However, under such conditions of submergence and increasing the quantity of
SOM, the degradation of soil quality because of the breakdown of stable aggregates
and deterioration of soil organic matter occurs. Crop rotations are known to favor
the enforcement of SOC and improving soil nutrients comparing to monocultures.
Continuous monoculture will not be active in sequestering C [25]. It is stated that
in the past decades, the SOC declined in high-yielding cropping systems, especially
in rice production systems, due to using chemical fertilizers and pesticides instead
cover crops and organic mature to retain crop growth and to increase grain yields [17].
However, SOC accumulation was attributed to the increased application of chemical
fertilizers that stimulate greater rice yields, higher biomass production, and higher
returning of crop residues to the soil, over the last several decades [23].
Owing to its high accumulation rate of SOC, rice cultivation may play a substantial
role in mitigation CO 2 in the atmosphere [23]. The dynamics of soil carbon (C) and
nitrogen (N) in submerged rice soils are different from those of aerobic, because
of maintaining submerged rice soils at lower redox potentials. Recently, stagnation
or decline in yields has been observed worldwide under the intensive rice-based
cultivation systems; this is attributed to the loss of quality and quantity of SOC
which influenced nutrient supply, specifically N [3]. It is reported that SOC in the
surface layer (0–20 cm) of paddy field is higher than its corresponding in the upland
croplands. They explained that the strong aggregate stability of paddy soil boosts
the SOC conservation and the enrichment of SOC in macro-aggregates, resulting in
a greater carbon sequestration potential in this soil. They also reported a declining
tendency of SOC after paddy conversion into the vegetable field [26].
On the other hand, rice agriculture contributes meaningfully to global straw production. These agricultural residues are spread in the field, removed from the field,
burned in situ, piled, incorporated to the soil, or mulched on the next crop. In the
past, straw was regularly removed from the field and used as fuels or construction