title: Conversion from rice to vegetable production increases N2O emission via increased soil organic matter mineralization.
abstract: The conversion from rice to vegetable production widely occurs in China. However, the effects of this conversion on N2O emission and the underlying mechanisms are not well understood. In the present study, 12 rice paddies (R) were selected and half of them converted to vegetable fields (V) with the following treatments: rice paddies without N-fertilizer (R-CK), rice paddies with conventional N-fertilizer (R-CN), converted vegetable fields without N-fertilizer (V-CK), and converted vegetable fields with conventional N-fertilizer (V-CN) in a randomized block design with 3 replicates. N2O emissions were measured with static chambers from December 2012 to December 2015. Within each V-CN plot, a root exclusion subplot was established to measure soil heterotrophic respiration (CO2effluxes), a proxy for soil organic matter mineralization. Conversion of rice paddies to vegetable production dramatically increased N2O emissions. The three-year cumulative N2O emissions were 0.59, 1.90, 55.50 and 160.14kg N ha-1for R-CK, R-CN, V-CK and V-CN, respectively. The annual N2O emissions from vegetable fields ranged between 5.99 and 113.45kg N ha-1yr-1, with substantially higher emissions in the first year. N2O fluxes from V-CN were significantly and positively related to CO2fluxes and inorganic N concentrations. The linear relationship between natural logarithms of N2O and CO2fluxes was stronger and the regression coefficient higher in the first year, showing the dependence of N2O on soil organic matter mineralization. These results suggest that soil organic matter and N mineralization contributes significantly to N2O emission following conversion of rice paddies to vegetable production.
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wu
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Shuirong
authors.initials: S
authors.lastname: Tang
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Dongdong
authors.initials: D
authors.lastname: He
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xian
authors.initials: X
authors.lastname: Wu
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Shaaban
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Milan
authors.initials: M
authors.lastname: Wang
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jingsong
authors.initials: J
authors.lastname: Zhao
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Imran
authors.initials: I
authors.lastname: Khan
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xunhua
authors.initials: X
authors.lastname: Zheng
authors.affiliation: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: rghu@mail.hzau.edu.cn.
authors.forename: Ronggui
authors.initials: R
authors.lastname: Hu
authors.affiliation: Department of Land, Air and Water Resources, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: Horwath
mesh_terms: D000383:Agriculture / Q000379:methods*; D000393:Air Pollutants / Q000032:analysis*; D002681:China; D004784:Environmental Monitoring; D005308:Fertilizers / Q000032:analysis; D009609:Nitrous Oxide / Q000032:analysis*; D012275:Oryza / Q000254:growth & development; D012987:Soil; D014675:Vegetables / Q000254:growth & development
chemical_list: D000393:Air Pollutants; D005308:Fertilizers; D012987:Soil; D009609:Nitrous Oxide
keywords: Inter-annual variation; Land management change; Organic matter mineralization; Soil N(2)O emission