title: Effects of nitrogen application rates on net annual global warming potential and greenhouse gas intensity in double-rice cropping systems of the Southern China.
abstract: The net global warming potential (NGWP) and net greenhouse gas intensity (NGHGI) of double-rice cropping systems are not well documented. We measured the NGWP and NGHGI including soil organic carbon (SOC) change and indirect emissions (IE) from double-crop rice fields with fertilizing systems in Southern China. These experiments with three different nitrogen (N) application rates since 2012 are as follows: 165 kgN ha-1for early rice and 225 kgN ha-1for late rice (N1), which was the local N application rates as the control; 135 kgN ha-1for early rice and 180 kgN ha-1for late rice (N2, 20 % reduction); and 105 kgN ha-1for early rice and 135 kgN ha-1for late rice (N3, 40 % reduction). Results showed that yields increased with the increase of N application rate, but without significant difference between N1 and N2 plots. Annual SOC sequestration rate under N1 was estimated to be 1.15 MgC ha-1year-1, which was higher than those under other fertilizing systems. Higher N application tended to increase CH4emissions during the flooded rice season and significantly increased N2O emissions from drained soils during the nonrice season, ranking as N1 > N2 > N3 with significant difference (P < 0.05). Two-year average IE has a huge contribution to GHG emissions mainly coming from the higher N inputs in the double-rice cropping system. Reducing N fertilizer usage can effectively decrease the NGWP and NGHGI in the double-rice cropping system, with the lowest NGHGI obtained in the N2 plot (0.99 kg CO2-eq kg-1yield year-1). The results suggested that agricultural economic viability and GHG mitigation can be simultaneously achieved by properly reducing N fertilizer application in double-rice cropping systems.
authors.affiliation: College of Agronomy and Biotechnology, China Agricultural University Key Laboratory of Farming System, Ministry of Agriculture, China, Beijing, 100193, China.
authors.forename: Zhongdu
authors.initials: Z
authors.lastname: Chen
authors.affiliation: College of Agronomy and Biotechnology, China Agricultural University Key Laboratory of Farming System, Ministry of Agriculture, China, Beijing, 100193, China. chenfu@cau.edu.cn.|College of Agronomy and Biotechnology, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian District, Beijing, 100193, China. chenfu@cau.edu.cn.
authors.forename: Fu
authors.initials: F
authors.lastname: Chen
authors.affiliation: College of Agronomy and Biotechnology, China Agricultural University Key Laboratory of Farming System, Ministry of Agriculture, China, Beijing, 100193, China.
authors.forename: Hailin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: College of Agronomy and Biotechnology, China Agricultural University Key Laboratory of Farming System, Ministry of Agriculture, China, Beijing, 100193, China.
authors.forename: Shengli
authors.initials: S
authors.lastname: Liu
mesh_terms: D000383:Agriculture / Q000379:methods*; D002681:China; D017753:Ecosystem; D005308:Fertilizers / Q000032:analysis; D057232:Global Warming; D017752:Greenhouse Effect; D008697:Methane / Q000032:analysis; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis; D012275:Oryza / Q000254:growth & development* / Q000378:metabolism; D012621:Seasons
chemical_list: D005308:Fertilizers; D009609:Nitrous Oxide; D009584:Nitrogen; D008697:Methane
keywords: Global warming; NGHGI; NGWP; Nitrogen application rates; Rice paddy; SOC stocks