155
9.5 Conclusions and Recommendations
Lowland rice contributes 10% of the global agricultural GHGEs due to CH 4 production from anaerobic decomposition of organic material. Straw management is therefore a key factor for controlling global agricultural emissions. Incorporating rice
straw under flooded conditions leads to high CH 4 emissions. Burning, although a
standard practice with lower GHGEs than incorporating, is not considered a CSA
option due to its negative effect on soil nutrients, SOC, and air pollution. Water
management through AWD is a major GHG mitigation strategy that can reduce 48%
of the CH 4 and thus is an effective method to reduce emissions when straw is incorporated under flooded conditions. AWD in combination with early incorporation
can further reduce CH 4 emissions by 80%. The rate of straw incorporation to achieve
CSA, however, is highly dependent on environment. Rice–upland crop rotations or
rice systems with prolonged fallow periods benefit from greater rates of straw incorporation due to losses in SOC. High rates of straw incorporation under aerobic conditions can sequester SOC with a minimal increase in emissions compared to
incorporation under flooded conditions. Practices that optimize SOC sequestration
while minimizing emissions, such as early straw incorporation with AWD water
management could be an important step towards carbon neutral rice systems.
Off-field practices such as composting, biochar, and bioenergy offer potentially
larger mitigation opportunities than in-field practices. Composting, for example,
can mitigate both emissions associated with fresh straw incorporation and those
associated with livestock manure and fertilizer use. The combination of biochar
and compost can further enhance mitigation. Although effective, off-field technologies may be limited due to the added costs of straw transport, capital equipment
and labor.
Depending on site-specific conditions related to economics, climate, soil type,
and infrastructure, a combination of off-field and in-field straw management practices is needed to reduce emissions from rice production. More holistic and crosssectoral studies, e.g., through life-cycle assessment, are needed to determine the full
GHG budget of certain site-specific straw management options. Additionally,
MACC and CBA studies would be important to develop clear technical and policy
recommendations that also consider the economics of CSA and straw management.
References
Arai T, Takaya T, Ito Y, Hayakawa K, Tshima S, Shibuya C, Nomura M, Yoshimi N, Hibayama M,
Yasuda Y (1998) Bronchial asthma induced by rice. Intern Med 37:98–101
Arai H, Hosen Y, Pham Hong VN, Thi NT, Huu CN, Inubushi K (2015) Greenhouse gas emissions
from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the
Mekong Delta. Soil Sci Plant Nutr 61:719–735
9 Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation…
9.5 Conclusions and Recommendations
Lowland rice contributes 10% of the global agricultural GHGEs due to CH 4 production from anaerobic decomposition of organic material. Straw management is therefore a key factor for controlling global agricultural emissions. Incorporating rice
straw under flooded conditions leads to high CH 4 emissions. Burning, although a
standard practice with lower GHGEs than incorporating, is not considered a CSA
option due to its negative effect on soil nutrients, SOC, and air pollution. Water
management through AWD is a major GHG mitigation strategy that can reduce 48%
of the CH 4 and thus is an effective method to reduce emissions when straw is incorporated under flooded conditions. AWD in combination with early incorporation
can further reduce CH 4 emissions by 80%. The rate of straw incorporation to achieve
CSA, however, is highly dependent on environment. Rice–upland crop rotations or
rice systems with prolonged fallow periods benefit from greater rates of straw incorporation due to losses in SOC. High rates of straw incorporation under aerobic conditions can sequester SOC with a minimal increase in emissions compared to
incorporation under flooded conditions. Practices that optimize SOC sequestration
while minimizing emissions, such as early straw incorporation with AWD water
management could be an important step towards carbon neutral rice systems.
Off-field practices such as composting, biochar, and bioenergy offer potentially
larger mitigation opportunities than in-field practices. Composting, for example,
can mitigate both emissions associated with fresh straw incorporation and those
associated with livestock manure and fertilizer use. The combination of biochar
and compost can further enhance mitigation. Although effective, off-field technologies may be limited due to the added costs of straw transport, capital equipment
and labor.
Depending on site-specific conditions related to economics, climate, soil type,
and infrastructure, a combination of off-field and in-field straw management practices is needed to reduce emissions from rice production. More holistic and crosssectoral studies, e.g., through life-cycle assessment, are needed to determine the full
GHG budget of certain site-specific straw management options. Additionally,
MACC and CBA studies would be important to develop clear technical and policy
recommendations that also consider the economics of CSA and straw management.
References
Arai T, Takaya T, Ito Y, Hayakawa K, Tshima S, Shibuya C, Nomura M, Yoshimi N, Hibayama M,
Yasuda Y (1998) Bronchial asthma induced by rice. Intern Med 37:98–101
Arai H, Hosen Y, Pham Hong VN, Thi NT, Huu CN, Inubushi K (2015) Greenhouse gas emissions
from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the
Mekong Delta. Soil Sci Plant Nutr 61:719–735
9 Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation…