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 N2O 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 N2O for upland croplands and water regime-specific emission factors for irrigated rice paddies were adopted to estimate annual synthetic fertilizer N-induced direct N2O emissions (FIE-N2O) from Chinese croplands during 1980–2000. Annual FIE-N2O was estimated to be 115.7 Gg N2O–N year−1 in the 1980s and 210.5 Gg N2O–N year−1 in the 1990s, with an annual increasing rate of 9.14 Gg N2O–N year−1 over the period 1980–2000. Upland croplands contributed most to the national total of FIE-N2O, accounting for 79% in 1980 and 92% in 2000. Approximately 65% of the FIE-N2O emitted in eastern and southern central China.