Global warming potential of farmers' rice fields: applied alternate wetting and drying in Nueva Ecija [Philippines]
2012
Sander, B.O., [email protected] | Wassmann, R., International Rice Research Inst., Los Baños, Laguna (Philippines) | Asis, C.A., Philippine Rice Research Inst., Maligaya, Science City of Muñoz, Nueva Ecija (Philippines)
Alternate wetting and drying (AWD) is a water saving strategy in rice production. The main principle is to allow the field to dry to a certain extent before irrigating again. In this way, up to 30% of irrigation water can be saved and by not letting the water level fall below a certain threshold, that might reduce yield. The greenhouse gas (GHG) methane has a 25 times higher global warming potential (GWP) than carbon dioxide (calculated for a 100 years period). It is produced by methanogenetic bacteria under anaerobic conditions which exist in flooded rice fields. Aeration of the field (e.g. through drainage) inhibits these bacteria. Thus, AWD can reduce methane emissions by up to 50%. A major concern is a possible increase in nitrous oxide emissions when applying AWD due to triggered nitrification/denetrification processes. AWD has been adopted in many rice producing areas already. All studies presented so far, however, have been done on experimental stations. In order to prove the impact of AWD on GHG mitigation, measurements on farmers' fields are necessary. In this study, the authors analyzed methane and nitrous oxide emissions from 12 rice fields in Nueva Ecija in DS 2010 and 2011. Six farms had adopted AWD and in another six farms, rice was grown in continuously flooded conditions. A survey with the participating farmers was conducted to support the experimental findings. The seasonal GHG fluxes as well as the influence of water management on the GWP of rice paddy are presented.
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