Estimation Of N₂O Emission In Anhui Agricultural Land

N₂O has a long residence time in the atmosphere,and a strong greenhouse effect.The N₂O sources are from nature?such as oceans and natural vegetation soil,ect.?and anthropogenic activities?such as fertilization,industrial production,etc.?.According to IPCC Fifth Assessment Report,the current global N₂O is increasing at an annual rate of0.73 ± 0.03 ppb.Where,agricultural activities are the most important anthropogenic sources of N₂O,accounting for 59%.According to report on Enabling China to Prepare Its Second National Communication to the UNFCCC,in 2005,73.79% of the N₂O emission is coming from agriculture in China,and of which fertilized soils contribute 52.9%.Anhui Province is located in the Yangtze River region.It is one of the major agricultural production bases in China.There are three significances by estimating N₂O emissions from Anhui croplands.Firstly,it can serve as a model for the calculation of N₂O emissions inventories for agricultural land in east China provincial.Secondly,the uncertainty of estimation of agricultural land N₂O emissions is reduced by using local or special parameters or informations.In addition,the research results can also provide a scientific basis for policy makers to make agricultural soils GHG mitigation measures in Anhui Province.In this study,the regional nitrogen cycle model IAP-N is used to estimate N₂O emissions from Anhui agricultural lands in 2011.N₂O emissions from agricultural lands include: direct N₂O emissions,indirect N₂O emissions,N₂O emissions from straws/residues field burning and total N₂O emissions.Among them,the direct emissions include direct N₂O emissions from different types of agricultural lands;indirect N₂O emissions include N₂O emissions which caused by atmospheric nitrogen deposition and caused by nitrogen leaching / runoff.Anhui Province is divided into four regions,based on its comprehensive geographical and climatic conditions,region I?Huaibei Plain?,region II?Jianghuai Hilly?,region III?along the dike mound?and region IV?mountain areas?.Based on the characteristics of cropping systems,Anhui Province croplands are divided into seven types: non-vegetable upland field,rice-upland rotation?dry crop planting season?,the upland rotation?rice planting season?,vegetable land,single paddy of rice + fallow,double paddy of rice + fallow and tea gardens and orchards.Agricultural statistics of all cities and counties in Anhui Province are obtained by querying the municipalities of Anhui Statistical Yearbook,and Anhui Province localized crop parameter data and animals' unitannually nitrogen excretion rate are obtained by inquiries literatures.The neighbor provinces' observations,which has the similary cropping systems,are selected to calculate the different types of farmland's direct emissions factors.The indirect factors of atmospheric nitrogen deposition into croplands are selected the corresponding croplands' direct emission factors,and the indirect emissions factors of N₂O emissions due to atmospheric nitrogen deposition into the outside of farmlands and N₂O emissions caused by nitrogen leaching/runoff are selected the default values of IPCC.N₂O emission factor of straw field burning is from the literature.The results are as followed:?1?The total N₂O emissions from Anhui croplands in 2011 was 35,100 t N₂O-N,equivalent to14,616,600 t CO2 eq,and its uncertainty is ± 44%.Direct emission was27,600 t N₂O-N,accounting for 79% of the total emissions.Indirect emission was 6,600 t N₂O-N,which two-thirds was caused by atmospheric nitrogen deposition and one-thirds was caused by leaching / runoff.N₂O emission from residues/straws burning in the field is the lowest,only 800 t N₂O-N with accounting for 2% of the total N₂O emissions in Anhui.?2?Huaibei Plain?Region I?and Jianghuai Hilly?Region II?were the main contribution regions in Anhui,accounting for 41% and 35% of its regional total N₂O emissions,respectively.Among them,the total N₂O emissions from Suzhou City and Huaiyuan County in region I,and Huoshan County and Shou County in region II were all over 1000 t N₂O-N.And the above four cities' and counties' N₂O total emissions were accounting for 16% of total emissions in Anhui Province.?3?For different types of agricultural land,the most important source for N₂O direct emission is the non-vegetable upland field with 74%.The second is rice-upland rotation fields with accounting for about 15%,of which,the N₂O emission in dry season is as twice as that in rice season.N₂O direct emissions from fields of single rice + fallow,vegetable and tea gardens and orchards,respectively,account for about 3.3 % of Anhui direct N₂O emissions;N₂O direct emissions from fields of double cropping of rice + fallow is lowest,accounting for 0.4%.In region I,94% N₂O direct emissions were from non-vegetable upland fields;while in other regions,the ratio is about 52%-63 %.The second N₂O direct emission source in Region II and Region III is the season of rice-upland rotation feilds,accounting for 19% and 14%,respectively.While in Region IV,the second direct N₂O emission source is tea gardens and orchards,accounting for 22%.?4?The average N₂O direct emission flux of Anhui croplands in 2011 is acreagely 2.0kg N₂O-N/ ha during crop growing season.Direct N₂O emission flux in growing season of different types of agricultural land are in the order of size as followed: tea gardens andorchards?4.2 kg N₂O-N/ha?>rice-upland rotation?dry crop planting season??2.6 kg N₂O-N/ha?> non-vegetable upland?2.2 kg N₂O-N/ha?> single cropping of rice + fallow?1.3 kg N₂O-N/ha?,rice-upland rotation?rice planting season??1.3 kg N₂O-N/ha?>vegetable land?1.1 kg N₂O-N/ha?> double cropping of rice + fallow?0.2 kg N₂O-N/ha?.