302
H. Elbasiouny and F. Elbehiry
fertilization, and organic amendment application could significantly affect N 2 O and
CH 4 flux [27].
Rice paddy fields play an important role in the global budget of GHGs, such as
CO 2 and CH 4 [10]. Rice farming systems tend to consume higher energy and have
a higher carbon footprint than many further comparable cropping systems. As well,
production, packaging, transportation, and the utilizing of extra farm inputs need
more energy. Subsequently it is likely to emit more GHGs. For example, since 1990–
2005, the global agriculture emissions increased by approximately 14%, an average
rate of 49 MtCO 2 e year
−1 [13]. Rice is an important emitter of CH 4 which contribute
to the warming as 19–25 times higher than that of CO 2 per unit of weight based on
100-year global warming potentials [32]. Rice production does not only play a major
role in sustaining global food security, creates wealth and jobs in the cultivating areas,
but also results in significant environmental impacts such as atmospheric GHG emissions [7, 31]. It is mentioned that CH 4 is produced by methanogens in flooded soil and
released to the atmosphere through the rice growing season. N 2 O is produced by nitrification and denitrification processes primarily from agricultural soil management
activities, such as OM application, fertilization, and irrigation. They added that the
global paddy rice cultivation in 2000–2010 emitted 22–25 Mt CH 4 year
−1 (i.e. 472–
518 Mt CO 2 eq year
−1 ). The annual total non-CO 2 GHG emissions from agriculture
in 2000–2010 was reported to range from 4.6 to 5.1 Gt CO 2 eq year
−1 , representing 57% from N 2 O emission and 43% from CH 4 emission. Approximately, 75% of
worldwide rice production is performed in continuously flooded paddies. Farmers
believe that this practice has many advantages such as retaining soil moisture and
temperature, increasing soil C, and suppressing the soil-borne disease and weeds.
However, flooding causes anaerobic conditions and therefore promotes methanogenesis and methane emissions [8, 10, 13]. It is also emphasized on paddy rise and
pond aquaculture as major sources of atmospheric CH 4 and N 2 O, mainly due to
the periodic dry/wet alteration episodes and intensive inputs of organic material and
nitrogen fertilizers [28]. Methane emissions from flooded-rice cultivation have been
revealed to be affected by various soil and plant properties, especially soil texture,
soil management practices, former crop, and selected cultivars. They also mentioned
that up to 90% of the produced CH 4 in flooded-rice cultivation is emitted into the
atmosphere. The remaining 10% of CH 4 in the soil is often re-oxidized into CO 2 and
released into the atmosphere. Methane emissions are differentially regulated by rice
growth stage and vary extensively among rice cultivars such as hybrids, inbred lines,
and conventional ones. This variation is a result of physiological differences among
cultivars in the production of CH 4 and methanotrophic activity in the rhizosphere
[31].
Furthermore, rice stubble is left on the ground to decay or burnt to ashes, which
is likely to produce both CH 4 and N 2 O emissions [13]. The Intergovernmental Panel
on Climate Change [7, 32, 33] estimated the annual global emission rate from paddy
fields averages 60 Tg year
−1 , with a range of 20–100 Tg year
−1 which counted
about 5–20% of the total CH 4 emissions from anthropogenic sources. This figure
is primarily based on field measurements from different paddy fields in different
countries such as the United States, Spain, Italy, China, India, Australia, Japan, and
H. Elbasiouny and F. Elbehiry
fertilization, and organic amendment application could significantly affect N 2 O and
CH 4 flux [27].
Rice paddy fields play an important role in the global budget of GHGs, such as
CO 2 and CH 4 [10]. Rice farming systems tend to consume higher energy and have
a higher carbon footprint than many further comparable cropping systems. As well,
production, packaging, transportation, and the utilizing of extra farm inputs need
more energy. Subsequently it is likely to emit more GHGs. For example, since 1990–
2005, the global agriculture emissions increased by approximately 14%, an average
rate of 49 MtCO 2 e year
−1 [13]. Rice is an important emitter of CH 4 which contribute
to the warming as 19–25 times higher than that of CO 2 per unit of weight based on
100-year global warming potentials [32]. Rice production does not only play a major
role in sustaining global food security, creates wealth and jobs in the cultivating areas,
but also results in significant environmental impacts such as atmospheric GHG emissions [7, 31]. It is mentioned that CH 4 is produced by methanogens in flooded soil and
released to the atmosphere through the rice growing season. N 2 O is produced by nitrification and denitrification processes primarily from agricultural soil management
activities, such as OM application, fertilization, and irrigation. They added that the
global paddy rice cultivation in 2000–2010 emitted 22–25 Mt CH 4 year
−1 (i.e. 472–
518 Mt CO 2 eq year
−1 ). The annual total non-CO 2 GHG emissions from agriculture
in 2000–2010 was reported to range from 4.6 to 5.1 Gt CO 2 eq year
−1 , representing 57% from N 2 O emission and 43% from CH 4 emission. Approximately, 75% of
worldwide rice production is performed in continuously flooded paddies. Farmers
believe that this practice has many advantages such as retaining soil moisture and
temperature, increasing soil C, and suppressing the soil-borne disease and weeds.
However, flooding causes anaerobic conditions and therefore promotes methanogenesis and methane emissions [8, 10, 13]. It is also emphasized on paddy rise and
pond aquaculture as major sources of atmospheric CH 4 and N 2 O, mainly due to
the periodic dry/wet alteration episodes and intensive inputs of organic material and
nitrogen fertilizers [28]. Methane emissions from flooded-rice cultivation have been
revealed to be affected by various soil and plant properties, especially soil texture,
soil management practices, former crop, and selected cultivars. They also mentioned
that up to 90% of the produced CH 4 in flooded-rice cultivation is emitted into the
atmosphere. The remaining 10% of CH 4 in the soil is often re-oxidized into CO 2 and
released into the atmosphere. Methane emissions are differentially regulated by rice
growth stage and vary extensively among rice cultivars such as hybrids, inbred lines,
and conventional ones. This variation is a result of physiological differences among
cultivars in the production of CH 4 and methanotrophic activity in the rhizosphere
[31].
Furthermore, rice stubble is left on the ground to decay or burnt to ashes, which
is likely to produce both CH 4 and N 2 O emissions [13]. The Intergovernmental Panel
on Climate Change [7, 32, 33] estimated the annual global emission rate from paddy
fields averages 60 Tg year
−1 , with a range of 20–100 Tg year
−1 which counted
about 5–20% of the total CH 4 emissions from anthropogenic sources. This figure
is primarily based on field measurements from different paddy fields in different
countries such as the United States, Spain, Italy, China, India, Australia, Japan, and