Agriculture is the main source of methane (CH4) and nitrous oxide (N2O) emissions. CH4 emissions from domestic ruminants, animal waste and rice fields were estimated to be 65-100 (IPCC, 1992; Hogan, 1993), 20-30 (Safley et al., 1992) and 25.4-54 (IPCC, 1996) Tg/yr. N2O is produced primarily by microbial processes in the soil (Bouwman, 1990; Duxbury and Mosier, 1993). It was estimated that more than 75% of the anthropogenic N2O sources are derived from agriculture, the total amount was 4.2Tg N2O-N/yr (Mosier et al., 1998b). A significant fraction of the CH4 and N2O emitted from agricultural systems could be avoided if some combination of agricultural management practices listed in Table 11.2 were adopted worldwide (IPCC, 1996).
|Table 11.2 List of practices to reduce CH4 and N2O emissions from agricultural systems (IPCC, 1996)|
|Mitigation practice||Estimated decrease due to practice (Tg CH4 or N2O-N/yr)|
Beyond the use of biomass fuels to displace fossil fuels, the management of forests, agricultural lands and rangelands can play an important role in reducing current emissions of CO2, CH4 and N2O, and in enhancing carbon sinks. A number of measures could conserve and sequester substantial amounts of methane (approximately 24-92 Tg/yr, 15-65% of current levels) over the next century (Mosier et al., 1998a). A total potential reduction of global N2O emissions from agricultural soils is thus 0.7 (0.36 to 1.1) Tg N2O-N/yr or 9-26% of current emissions from agriculture (Mosier et al., 1998b).
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