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Methane emissions from rained rice fields

: Wassmann, R.; Neue, H.U.; Lantin, R.S.; Javellana, M.J.; Diego, R.; Lignes, V.E.; Hoffmann, H.; Papen, H.; Rennenberg, H.

International Rice Research Institute -IRRI-:
Fragile lives in fragile ecosystems. Proceedings of the 22. International Rice Research Conference
Los Banos, Laguna: IRRI, 1995
ISBN: 971-22-0073-6
S.217-225 : Ill., Lit.
International Rice Research Conference <22, 1995, Los Banos/Laguna, Phillippines>
Fraunhofer IFU; 2002 in Helmholtz-Gesellschaft integriert

This experiment encompassed three treatments with varying water regimes representing irrigated rice with assured flooding and two types of rainfed rice a ffected by droughts. Methane emission was recorded by an automatic closed chamber system facilitating continuous measurements over the entire dry and wet season of 1994. The methane emission rates in the dry season were generally higher than in the wet season; the seasonal patterns of methane emission in the individual treatments showed a high degree of similarity in both seasons. Mid-tillering drainage prompted a pronounced decrease in methane emission rates which was attributed to the influx of oxygen into the soil. Low methane fluxes prevailed even after the field was reflooded. In the other treatments, which were kept flooded during tillering stage, methane emission rates stayed relatively constant. Drainage at 14 days before harvest prompted a short-term increase of methane emission rate which was attributed to a degassing of soi l entrapped methane. In the field that was flooded throughout the growing season, the process of harvesting was also associated with the short-term release of large amounts of methane. The results of this experiment demonstrate that 1) rainfed rice has a lower emission potential than irrigated rice, 2) the impact of droughts on methane emission depends on the actual growing stage the drought occurs, 3) methane emission from rainfed rice will increase with advances gained in water supply, and 4) temporary drainage can be an effective measure to reduce methane emission from rice.