Estimates of synthetic fertilizer N-induced direct nitrous oxide emission from Chinese croplands during 1980-2000.

There is increasing concern that agricultural intensification in China has greatly increased N(2)O emissions due to rapidly increased fertilizer use. By linking a spatial database of precipitation, synthetic fertilizer N input, cropping rotation and area via GIS, a precipitation-rectified emission factor of N(2)O for upland croplands and water regime-specific emission factors for irrigated rice paddies were adopted to estimate annual synthetic fertilizer N-induced direct N(2)O emissions (FIE-N(2)O) from Chinese croplands during 1980-2000. Annual FIE-N(2)O was estimated to be 115.7 Gg N(2)O-N year(-1) in the 1980s and 210.5 Gg N(2)O-N year(-1) in the 1990s, with an annual increasing rate of 9.14 Gg N(2)O-N year(-1) over the period 1980-2000. Upland croplands contributed most to the national total of FIE-N(2)O, accounting for 79% in 1980 and 92% in 2000. Approximately 65% of the FIE-N(2)O emitted in eastern and southern central China.