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Effects of nitrogen fertilization on CH₄ emissions from rice fields
- CAI, Zucong, SHAN, Yuhua, XU, Hua
- Soil science and plant nutrition 2007 v.53 no.4 pp. 353-361
- adverse effects, carbon, ecosystems, emissions factor, fertilizer application, grain yield, greenhouse gas emissions, methane, methane production, nitrogen, nitrogen fertilizers, nitrous oxide, oxidation, paddies, rice, soil
- Nitrogen fertilization is essential for achieving high rice yields and is widely practiced in rice cultivation. There is an ongoing discussion on the possible effects of N application on CH₄ emission from rice fields. CH₄ emission is a net consequence of CH₄ production, oxidation and transport from the soil in which the CH₄ is produced to the atmosphere, and the interactions among these processes. Nitrogen influences all the processes of CH₄ emission from rice fields either directly or indirectly and the effects are either negative or positive at the ecosystem, microbial and biochemical level. Because of this complexity and counter-balance among the effects, it is difficult to assess the net N effect on CH₄ emissions from rice fields on a national or global scale. Field measurements also show a contradiction in that positive, negative and no effects of N application on CH₄ emissions have been observed. Nevertheless, it is clear that the effect of N application on CH₄ emission is N-form dependent. Nitrate-based fertilizers are able to mitigate CH₄ emission, but they are rarely applied to rice fields and generally not practicable to mitigate CH₄ emission because of their low use efficiency and stimulatory effect on N₂O emission. In contrast, the application of organic N stimulates CH₄ emission because additional organic carbon is supplied for CH₄ production. However, it is not sufficient to conclude that CH₄ emission intensity would have been decreased by the replacement of organic N, which dominated traditional rice cultivations, with chemical N fertilizers, which are used in current rice cultivations, because the fertilizer replacement has also enhanced rice yields, which in turn affects CH₄ production, oxidation and transport. Establishing quantitative relationships between N status in soil and CH₄ production, oxidation and transport is essential to assess the effects of chemical N fertilizer application on CH₄ emissions from rice fields.