Pedosphere 24(2): 186--195, 2014
ISSN 1002-0160/CN 32-1315/P
©2014 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Nitrogen isotopic fractionation related to nitrification capacity in agricultural soils |
SONG Ge1,3, ZHAO Xu1,2 , WANG Shen-Qiang1,2 and XING Guang-Xi1 |
1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2
Changshu National Agro-Ecosystem Observation and Research Station, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
3University of Chinese Academy of Sciences, Beijing 100049 (China) |
| ABSTRACT |
| A laboratory-based aerobic incubation was conducted to investigate nitrogen (N) isotopic fractionation related to nitrification in five agricultural soils after application of ammonium sulfate ((NH4)2SO4). The soil samples were collected from a subtropical barren land soil derived from granite (RGB), three subtropical upland soils derived from granite (RQU), Quaternary red earth (RGU), Quaternary Xiashu loess (YQU) and a temperate upland soil generated from alluvial deposit (FAU). The five soils varied in nitrification potential, being in the order of FAU >YQU > RGU > RQU > RGB. Significant N isotopic fractionation accompanied nitrification of NH4+. δ15N values of NH4+ increased with enhanced nitrification over time in the four upland soils with NH4+ addition, while those of NO3- decreased consistently to the minimum and thereafter increased. δ15N values of NH4+ showed a significantly negative linear relationship with NH4+-N concentration, but a positive linear relationship with NO3--N concentration. The apparent isotopic fractionation factor calculated based on the loss of NH4+ was 1.036 for RQU, 1.022 for RGU, 1.016 for YQU, and 1.020 for FAU, respectively. Zero- and first-order reaction kinetics seemed to have their limitations in describing the nitrification process affected by NH4+ input in the studied soils. In contrast, N kinetic isotope fractionation was closely related to the nitrifying activity, and might serve as an alternative tool for estimating the nitrification capacity of agricultural soils. |
| Key Words: NH4+ addition, nitrification, nitrogen isotope fractionation, reaction kinetics |
| Citation: Song, G., Zhao, X., Wang, S. Q. and Xing, G. X. 2014. Nitrogen isotopic fractionation related to nitrification capacity in agricultural soils. Pedosphere. 24(2): 186-195. |
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