Direct nitrous oxide emissions from agricultural fields in China estimated by the revised 1996 IPPC guidelines for national greenhouse gases

Using revised 1996 IPCC guidelines for national greenhouse gases and statistic data in China Agricultural Yearbook, we estimated the direct nitrous oxide (N₂O) emissions from agricultural fields in China for the following years: 1949, 1954, 1960, 1965, 1970, 1975, 1980, 1985, 1990 and 1995. Direct N₂O emissions have been increasing continuously, from 26 Gg N in 1949 to 336 Gg N in 1995, at a rate of 7 Gg N y⁻¹. The main reason for the rapid increase in N₂O emissions was the increase in the use of synthetic fertilizer, which contributed 0.28% to the total emissions from soils in 1949, compared with 73.7% in 1990.Modifications to some equations and parameters were made according the local agricultural practices, such as the type of crops, the use of crop residue, cultivation of leguminous green manure and the application of animal manure as fertilizer in China. The trend of direct N₂O emissions from agricultural fields in China is discussed in this paper.