Neue, H.-U., Becker-Heidmann, P., Scharpenseel, H.-W. (1990): Organic matter dynamics, soil properties and cultural practices in rice lands and their relationship to methane production. – In: Bouwman, A. F. (Hg.): Soils and the greenhouse effect, S. 457–466. Wiley, Chichester u.a.
The global rice area harvested in 1988 has been discriminated with regard to the major rice ecologies which are irrigated, rainfed, deepwater and upland. Net primary production of rice paddies is estimated to be 1,400 g m-2 y-1 of which 400 g m-2 y-1 is returned to the soil. Reliable data on additional inputs of organic substrates are not available but the global trend is decreasing. Soil related principles of methane formation have been identified and various soil properties are amalgamated into three crucial parameters (temperature, texture and mineralogy, Eh/pH buffer systems). Considering these soil characteristics and water regimes, only 80 million ha of harvested wetland rice lands are tentatively classified to be prone to methane formation. The global annual emission of methane from wetland rice fields is estimated to be 25-60 Tg.