Articles | Volume 18, issue 14
Atmos. Chem. Phys., 18, 10419–10431, 2018
Atmos. Chem. Phys., 18, 10419–10431, 2018

Research article 23 Jul 2018

Research article | 23 Jul 2018

Controlling variables and emission factors of methane from global rice fields

Jinyang Wang1,2, Hiroko Akiyama3, Kazuyuki Yagi3, and Xiaoyuan Yan1 Jinyang Wang et al.
  • 1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, People's Republic of China
  • 2Environment Centre Wales, School of the Environment, Natural Resources and Geography, Bangor University, Bangor, LL57 2UW, UK
  • 3Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, 3-1-3, Kannondai, Tsukuba, Ibaraki, 305-8604, Japan

Abstract. Rice cultivation has long been known as one of the dominant anthropogenic contributors to methane (CH4) emissions, yet there is still uncertainty when estimating its emissions at the global or regional scale. An increasing number of rice field measurements have been conducted globally, which allow us to reassess the major variables controlling CH4 emissions and develop region- and country-specific emission factors (EFs). The results of our statistical analysis show that the CH4 flux from rice fields was closely related to organic amendments, the water regime during and before the rice-growing season, soil properties and agroecological conditions. The average CH4 fluxes from fields with single and multiple drainage were 71 % and 55 % that of continuously flooded rice fields. The CH4 flux from fields that were flooded in the previous season were 2.4 and 2.7 times that of fields previously drained for a short and long season, respectively. Rice straw applied at 6 t ha−1 in the preseason can decrease CH4 emissions by half when compared to that applied shortly before rice transplanting. The global default EF was estimated to be 1.19 kg CH4 ha−1 day−1 with a 95 % confidence interval of 0.80 to 1.76 kg CH4 ha−1 day−1 for continuously flooded rice fields without organic amendment and with a preseason water status of short drainage. The lower EFs were found in countries from South Asia (0.85 kg CH4 ha−1 day−1) and North America (0.65 kg CH4 ha−1 day−1) relative to other regions, indicative of geographical variations at sub-regional and country levels. In conclusion, these findings can provide a sound basis for developing national inventories and mitigation strategies of CH4 emission from rice fields.

Short summary
Through reassessing the controlling variables and emission factors (EFs) of CH4 on a global scale, we find that the global default EF of CH4 is lower and has a narrow error range than the previous report. The region/country-specific EFs are for the first time developed. The findings of major controlling variables on CH4 emission may help to devise mitigation strategies at different scales. These default EFs and scaling factors can provide a sound basis for developing national CH4 inventories.
Final-revised paper