Analysis of N₂O emissions from the agro-ecosystem in Fujian Province

Nitrogen dioxide (N₂O) is a major greenhouse gas. Investigating N₂O emissions from agro-ecosystems of Fujian Province is critical for developing efficient mitigation strategies. Based on agricultural data in Fujian Province, a regional nitrogen cycle model, IAP-N, was adopted to estimate N₂O emissions (in nitrogen gauge) from agro-ecosystems in Fujian Province for the period 1991 2010. The results showed that N₂O emissions from agro-ecosystems (including direct and indirect farmland emissions, emissions from field-straw burning and animal manure) initially increased from 23 675.3 t·a^-1 in 1991 to 32 610.4 t·a^-1 in 2006 and then decreased to 30 810.7 t·a^-1 in 2010. Average annual N₂O emissions were 26 170.7 t·a^-1, 29 870.0 t·a^-1, 32 085.8 t·a^-1 and 31 287.6 t·a^-1 during 1991-1995, 1996-2000, 2001-2005, 2006-2010, respectively. The order of N₂O emissions from different sources was direct farmland (66.2%) > animal manure (20.7%) > indirect farmland (12.9%) > filed-straw burning (0.2%). Direct N₂O emissions from farmland increased from 15 108 t·a^-1 in 1991 to 21 547 t·a^-1 in 2006 and then decreased to 20 594 t·a^-1 in 2010. Average annual direct N₂O emissions from farmland were 17 073.0 t·a^-1, 19 976.8 t·a^-1, 21 183.4 t·a^-1 and 20 778.6 t·a^-1, respectively. Upland crops such as vegetables, non-vegetables upland and paddy-upland rotation systems were the primary sources, accounting for 83.0% 90.7% of direct N₂O emissions from farmlands. N₂O emission from animal manure was 5 213.2 6 988.0 t·a^-1 in 1991 2010, with no obvious changes. Pigs were the primary source of animal manure, accounting for 57.4% 67.9% of N₂O emissions from animal manure. In 2010, N₂O emissions from the agro-ecosystems mainly concentrated in Zhangzhou, Nanping, Quanzhou and Ningde Districts, with over 4 000 t·a^-1 N₂O emissions. These districts led N₂O emission rates in the study area, accounting for 61.7% of provincial emission. The results laid the scientific basis for policy decisions on fertilizer efficiency and N₂O emission mitigation in the agro-ecosystems in Fujian Province.