**7. Conclusion**

rice productivity by changing the management of plants, soil, water, and nutrients. Successful application of SRI of increased paddy yield by 50–100% while using less inputs, in particular water, (farmers were able to reduce their water requirements by about 25–50%) [42] has already been reported. Suitable rice cropping patterns, rotations, and mixed rice-duck-fish farming hold the potential scope to sustain agricultural productivity and controlling GHG emissions in the changing climatic conditions. For example, in the Philippines, fish or ducks have been raised with rice as well as legumes such as mung bean (*Vigna radiata*), groundnut (*Arachis hypogaea*), and soybean (*Glycine max*) after two rice dropping. Rotation of crops that have their most drought-sensitive phase in different phases of the growing season may prove a valuable adaptation to limited water resources. Haque et al. reported that the nonrice-based cropping patterns had lower GWPs than the rice-rice-based cropping patterns [43]. Ali et al.

by integrated rice duck farming [28]. It has been reported that azolla application in rice field

tems, probably due to the increase in redox potential in the root region and dissolved oxygen

to increase when crop residues are incorporated prior to planting due to higher amounts of readily available carbon stimulating soil microbial activity. Sander et al. reported that incorporation of rice residues immediately after harvest and subsequent aerobic decomposition of

also improved nutrient cycling in paddy field [45]. It was also reported that residue incor-

(ryegrass and serradella) left on the soil surface. The open burning of crop residues emits CO<sup>2</sup>

16–20% and increased rice yield by 13–18% in Korean paddy soil, whereas 12–21% reduction

yield scaled greenhouse gas emissions were decreased by combined application of Azollacyanobacterial mixture with silicate slag, phospho-gypsum, and biochar amendments in rice paddy soils of Japan, Korea, and Bangladesh (**Table 2**) [18]. Site-specific nutrient management (SSNM) for rice developed by IRRI (2006) in Asia [47] enables rice farmers to tailor nutrient management to the specific conditions of their fields, and provides a framework for nutrientbased management practices for rice. The increase in annual grain yield with use of SSNM in on-farm evaluation trials averaged 0.9 t/ha in southern India, 0.7 t/ha in the Philippines, and 0.7 t/ha in southern Vietnam [48]. Climatic stress tolerant rice cultivars such as drought, salt/ saline, and submergence tolerant rice cultivars have to be developed to cope in the real field stress situation. It was reported [49] that indica-type rice cultivars had significantly higher

with nitrogenous fertilizer in rice cultivation significantly decreased seasonal CH<sup>4</sup>

equiv. Mg−<sup>1</sup>

type rice cultivar. It was also reported that AWD irrigation practice reduced CH<sup>4</sup>

24–41%, 26–48% compared with continuous flooding, however, an increase in N<sup>2</sup>

O. Ali et al. [17] reported that silicate slag and phospho-gypsum amendments

flux and 5–18% increase in rice grain yield were found in the upland

emissions from wetland paddy ecosystems were significantly decreased

emission was also found from rice soil ecosys-

O emissions from irrigated rice field compared to residues

and N2

) compared to Japonica (711 kg CO<sup>2</sup>

O emission from rice pad-

O production through nitrification

emissions have been reported

emissions by 2.5–5 times and

O emissions, GWPs, and

equiv. Mg−<sup>1</sup>

emissions by

O emission

)-

,

flux by

emission, probably due to the exudation of azolla root and decomposition of

reported that CH4

poration accelerated CH4

, and N<sup>2</sup>

in total seasonal CH4

yield-scaled GWP (1101 kg CO<sup>2</sup>

CH4

dead azolla. In contrast, reverse report on CH<sup>4</sup>

102 Soil Contamination and Alternatives for Sustainable Development

concentration at the soil-water interface. Azolla cover increased N<sup>2</sup>

dies due to N-fixation by azolla providing a source for N<sup>2</sup>

and de-nitrification, especially when the azolla died [44]. CH4

the residues before soil flooding for the next crop reduced CH<sup>4</sup>

and N2

rice paddy soils of Bangladesh [46]. Seasonal cumulative CH<sup>4</sup>

increased CH4

In the context of global climate change, environment friendly agricultural management practices such as conservation tillage, rice seedling transplanting or direct line seeding, alternate wet and dry irrigation (AWDI), mid-season drainage, soil amendments with biochar, vermicompost, silicate slag and phospho-gypsum, site specific rice based cropping patterns and integrated plant nutrients system (IPNS) should be followed to ensure food security, while mitigating greenhouse gas emissions and global warming potentials. Furthermore, Azollacyanobacterial dual cropping with rice, introducing N-fixing legumes and duckling rearing with flood water rice cultivation could be practiced to sustain overall agricultural productivity and minimizing greenhouse gases intensity in the changing climatic conditions.
