Effects of nitrogen fertilizer on CH emission from rice fields: multi-site field observations

摘要

There is an ongoing discussion of the possible effects of nitrogen (N) application on methane (CH) emission from rice fields. However, the Intergovernmental Panel on Climate Change (IPCC) methodologies for estimating the national inventory of CH emission from paddy rice production do not consider the effects of N addition. To assess the lack of knowledge about N addition effects on inventory estimates, we recently launched a multi-site observation campaign in major rice cultivation regions of China. The observations showed that, across various climate zones, the application of ammonium-based fertilizers at the commonly-adopted levels for fields in China (150 or 250 kg N hap#) generally inhibited accumulative CH emission during rice season (by 28-30% on average) as compared to no N addition. An increase in application from the moderate level of 150 kg N hap# to the high rate of 250 kg N hap# did not significantly modify CH emission. Our results suggest that disregarding the effect of N fertilization by the IPCC methodologies may not significantly bias CH inventory estimates of China. In regions with much lower N addition levels, however, disregarding the effect of N fertilization may result in the underestimation of regional CH emission, since these emissions were mainly derived from studies in regions with relatively high N addition rates.