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posting, biochar, and others—under various rice production environments, such as
water management, cropping system, and soil type.
9.2 In-Field Straw Management Effects on Emissions
and Mitigation
9.2.1 Burning
Open-field burning of rice straw has well-known negative environmental and agronomic impacts due to atmospheric pollution and reduced soil quality. Burning also
emits GHGs CO 2 , CH 4 , and N 2 O, along with other trace gases that contribute to
tropospheric ozone and the formation of Atmospheric Brown Cloud (ABC)—a
cause of severe human health concern (Arai et al. 1998; Gullett and Touati 2003;
Lin et al. 2007; Tipayarom and Kim Oanh 2007; Torigoe et al. 2000; Kanokkanjana
et al. 2011). Still, studies suggest that the total GHGEs from burning are up to 98%
lower than those from fresh straw incorporation in flooded soils due to reductions in
CH 4 from straw decomposition (IPCC 2006). This accounting, however, excludes
CO 2 emissions, which are considered net neutral from photosynthesis in the IPCC
guidelines. When CO 2 is included, the carbon losses from burning reduce the SOC
sequestration potential of fresh straw incorporation due to the immediate 90% loss
of straw C as CO 2 during combustion (Chen et al. 2019). When this is accounted for,
the NGWP from burning is comparable to that of complete fresh straw incorporation (Lu et al. 2010).
SOC sequestration is thus an important component of emissions calculations
from burning. For example, a meta-analysis in China compared the effects of burning and straw incorporation on NGWP to include sequestration and found that
switching from burning to straw incorporation could mitigate 34.18 Mt. CO 2 eq
year
−1
or 31% of total rice emissions in the country (Lu 2015; Liu et al. 2014). This
assumed a large sequestration potential by restoring degraded soils to their maximum SOC storage ability or SOC saturation capacity (EPA 2013). Once saturation
was reached, the mitigation potential of straw incorporation diminished. Increasing
SOC not only mitigates emissions, but can also substantially improve soil quality,
yields, and adaptation to climate change by improving drought tolerance. For example, an only 1% improvement to SOM can double the soil water holding capacity
(Fileccia et al. 2014).
Despite the established negative long-term impacts of burning on soil quality,
SOC sequestration and air quality, intensive rice farmers prefer burning rice straw
due to lower costs, reduced weed and disease carryover, and ease of tillage.
Advantages of burning may decline as opportunities increase for off-farm uses and
stricter government environmental regulations encourage alternative options.
9 Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation…
posting, biochar, and others—under various rice production environments, such as
water management, cropping system, and soil type.
9.2 In-Field Straw Management Effects on Emissions
and Mitigation
9.2.1 Burning
Open-field burning of rice straw has well-known negative environmental and agronomic impacts due to atmospheric pollution and reduced soil quality. Burning also
emits GHGs CO 2 , CH 4 , and N 2 O, along with other trace gases that contribute to
tropospheric ozone and the formation of Atmospheric Brown Cloud (ABC)—a
cause of severe human health concern (Arai et al. 1998; Gullett and Touati 2003;
Lin et al. 2007; Tipayarom and Kim Oanh 2007; Torigoe et al. 2000; Kanokkanjana
et al. 2011). Still, studies suggest that the total GHGEs from burning are up to 98%
lower than those from fresh straw incorporation in flooded soils due to reductions in
CH 4 from straw decomposition (IPCC 2006). This accounting, however, excludes
CO 2 emissions, which are considered net neutral from photosynthesis in the IPCC
guidelines. When CO 2 is included, the carbon losses from burning reduce the SOC
sequestration potential of fresh straw incorporation due to the immediate 90% loss
of straw C as CO 2 during combustion (Chen et al. 2019). When this is accounted for,
the NGWP from burning is comparable to that of complete fresh straw incorporation (Lu et al. 2010).
SOC sequestration is thus an important component of emissions calculations
from burning. For example, a meta-analysis in China compared the effects of burning and straw incorporation on NGWP to include sequestration and found that
switching from burning to straw incorporation could mitigate 34.18 Mt. CO 2 eq
year
−1
or 31% of total rice emissions in the country (Lu 2015; Liu et al. 2014). This
assumed a large sequestration potential by restoring degraded soils to their maximum SOC storage ability or SOC saturation capacity (EPA 2013). Once saturation
was reached, the mitigation potential of straw incorporation diminished. Increasing
SOC not only mitigates emissions, but can also substantially improve soil quality,
yields, and adaptation to climate change by improving drought tolerance. For example, an only 1% improvement to SOM can double the soil water holding capacity
(Fileccia et al. 2014).
Despite the established negative long-term impacts of burning on soil quality,
SOC sequestration and air quality, intensive rice farmers prefer burning rice straw
due to lower costs, reduced weed and disease carryover, and ease of tillage.
Advantages of burning may decline as opportunities increase for off-farm uses and
stricter government environmental regulations encourage alternative options.
9 Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation…