**1. Introduction**

World rice production especially in Southeast Asia and tropical Asia is highly vulnerable to climate change. Rice production systems contribute to global climate change through emissions of carbon dioxide (CO<sup>2</sup> ), methane (CH<sup>4</sup> ), and N<sup>2</sup> O gases to the atmosphere and simultaneously are affected by the changed climatic variables. Rice is the major cereal crop for more than half of the world's population and its production needs to be increased 40% by the end of the 2030s to meet the increasing demand for the expanding population [1], which may further accelerate

million ha of cropland, where approximately 80 million ha were managed under continuous flood irrigation and contributed to 75% of the world's rice production [3]. China and India, most densely populated countries in the world, account for 20.0 and 28.5% of the global rice area, respectively [4]. In China, approximately 90% of the rice fields are irrigated [5], while in India, more than 46% of the rice fields are irrigated [6]. Unfortunately, the irrigated rice

[7]. Therefore, IRRI is promoting water-saving alternate wetting and drying techniques for

O) depending on soil organic matter status, land use and cropping intensity, irrigation water and drainage management practices, soil microbial populations and their activities, soil properties, and climatic variables. The management practices such as tillage operations, leveling, plant residue incorporation, irrigation frequency and standing water levels, drainage system, and organic and inorganic soil amendments followed in rice farming influence the amount of CH<sup>4</sup>

processes depending on soil aerobic (oxygenated) and anaerobic conditions (**Figure 1b**).

off relationship observed which is largely dependent on paddy soil water level, redox status, soil organic matter content, and external sources of organic and inorganic soil amendments.

and N2

with calcium carbide, phospho-gypsum, and silicate fertilizer amendments under continuous and intermittent irrigations, respectively [8]. However, biochar amendments increased the

O), have been contributing to about 80% to the current global radiative forcing [9]. Agricultural activities contribute to approximately 20% of the present concentrations of atmo-

toward global warming with almost 25-fold higher global warming potential than carbon

270 ppb in the pre-industrial period to 1853 and 328.9 ppb in 2016, respectively [12]. China, the largest rice-producing country, accounts for about 28% of global rice production [4] and

O gases, which simultaneously increased rice yield [8].

and N2

and N2

O emissions are low under flooded fields, while CH<sup>4</sup>

farming acts as one of the main sources of anthropogenic CH4

Rice paddy fields act as a source of greenhouse gases such as methane (CH<sup>4</sup>

improving water use efficiency, while reducing CH<sup>4</sup>

O emitted to the atmosphere. Generally, CH<sup>4</sup>

soil conditions (**Figure 1a**), while N<sup>2</sup>

Ali et al. reported that the total GWP of CH<sup>4</sup>

and N2

**2. Climatic change and greenhouse gas emissions**

Greenhouse gases (GHGs), mainly carbon dioxide (CO<sup>2</sup>

spheric GHGs [10], especially the emissions of CH<sup>4</sup>

global-warming potentials (GWP) of 25 and 298 CO<sup>2</sup>

dioxide [11]. The concentrations of atmospheric CH<sup>4</sup>

time horizon. Apart from the water vapor, CH<sup>4</sup>

) and nitrous oxide (N2

O emissions to the atmosphere [2]. In 2012, worldwide rice production covered 163

Management of Paddy Soil towards Low Greenhouse Gas Emissions and Sustainable Rice…

emission to the atmosphere

http://dx.doi.org/10.5772/intechopen.83548

91

emissions are high, a trade-

), and nitrous oxide

O from paddy fields [9]. Methane

O have increased from 722 and


is a major greenhouse gas contributing 20%

) and nitrous oxides

production in the rice rhizosphere.

gas is produced under flooded or anoxic

O gases was decreased by 7–27% and 6–34%

O gas is produced through nitrification and denitrification

), methane (CH<sup>4</sup>

O) are the two most important GHGs from agriculture, with

CH4

(N2

and N2

(N2

(CH4

Typically, N<sup>2</sup>

overall GWP of CH<sup>4</sup>

and N2

**Figure 1.** (a) Schematic diagram of methane production, oxidation, and emission from rice paddy field and (b) schematic diagram of N2 O, NO, and N<sup>2</sup> emissions from rice paddy field.

are affected by the changed climatic variables. Rice is the major cereal crop for more than half of the world's population and its production needs to be increased 40% by the end of the 2030s to meet the increasing demand for the expanding population [1], which may further accelerate CH4 and N2 O emissions to the atmosphere [2]. In 2012, worldwide rice production covered 163 million ha of cropland, where approximately 80 million ha were managed under continuous flood irrigation and contributed to 75% of the world's rice production [3]. China and India, most densely populated countries in the world, account for 20.0 and 28.5% of the global rice area, respectively [4]. In China, approximately 90% of the rice fields are irrigated [5], while in India, more than 46% of the rice fields are irrigated [6]. Unfortunately, the irrigated rice farming acts as one of the main sources of anthropogenic CH4 emission to the atmosphere [7]. Therefore, IRRI is promoting water-saving alternate wetting and drying techniques for improving water use efficiency, while reducing CH<sup>4</sup> production in the rice rhizosphere.

Rice paddy fields act as a source of greenhouse gases such as methane (CH<sup>4</sup> ) and nitrous oxides (N2 O) depending on soil organic matter status, land use and cropping intensity, irrigation water and drainage management practices, soil microbial populations and their activities, soil properties, and climatic variables. The management practices such as tillage operations, leveling, plant residue incorporation, irrigation frequency and standing water levels, drainage system, and organic and inorganic soil amendments followed in rice farming influence the amount of CH<sup>4</sup> and N2 O emitted to the atmosphere. Generally, CH<sup>4</sup> gas is produced under flooded or anoxic soil conditions (**Figure 1a**), while N<sup>2</sup> O gas is produced through nitrification and denitrification processes depending on soil aerobic (oxygenated) and anaerobic conditions (**Figure 1b**).

Typically, N<sup>2</sup> O emissions are low under flooded fields, while CH<sup>4</sup> emissions are high, a tradeoff relationship observed which is largely dependent on paddy soil water level, redox status, soil organic matter content, and external sources of organic and inorganic soil amendments. Ali et al. reported that the total GWP of CH<sup>4</sup> and N2 O gases was decreased by 7–27% and 6–34% with calcium carbide, phospho-gypsum, and silicate fertilizer amendments under continuous and intermittent irrigations, respectively [8]. However, biochar amendments increased the overall GWP of CH<sup>4</sup> and N2 O gases, which simultaneously increased rice yield [8].
