Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8363990 | Soil Biology and Biochemistry | 2015 | 17 Pages |
Abstract
The rainfall event triggered N2O production in both fields at all depths, but the uppermost soil layer was the main source of N2O emissions throughout. Soil concentrations and surface emissions of N2O increased rapidly reaching a maximum 4 d following rainfall and were accompanied by a significant increase in the abundance of both nitrifier and denitrifier genes and total bacterial and archaeal genes and transcripts. A similar increase in the transcription of functional genes was not detected, but relatively high levels of archaeal ammonia monooxygenase (crenamoA) and bacterial nitrite reductase (nirS) transcripts were present in both fields throughout the study, indicating nitrification and denitrification were occurring concomitantly. High levels of H2O-NOx oxygen exchange at our study site precluded the use of δ18O-N2O values to separate different sources. Prior to the rain, both fields had very small amounts of soil ammonium and the stable nitrogen isotope characterization of N2O in the dry soil implicated denitrification as the main source of N2O rather than nitrifier-denitrification or hydroxylamine oxidation. Following the rain event, the δ15N-N2O values showed a change in production process as nitrifier-denitrification became a more dominant N2O source. By pairing stable isotope measurements with molecular analyses we were able to verify that these two approaches provide similar inferences about soil N2O production processes during an emission event in manure-applied fields. Although significantly higher N2O flux and N2O accumulation in the soil profile were observed for the field receiving manure in the spring, differences in isotope signal and molecular analysis between fields were not observed. To our knowledge this is the first time that isotope and molecular techniques have been used to study processes resulting in N2O production in manure-amended soils in situ. Whereas stable isotopes were useful for directly tracking the pathways of N2O production, molecular analyses revealed the status of the N cycling communities before, during and after the emission event. This information helped explain the observed differences in emissions between fields, and it helped to support our isotope-based conclusions.
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Agricultural and Biological Sciences
Soil Science
Authors
David Snider, Karen Thompson, Claudia Wagner-Riddle, John Spoelstra, Kari Dunfield,