CH4 oxidation and emissions of CH4 and N 2O from Lolium perenne swards under elevated atmospheric CO 2

E. M. Baggs, H. Blum

Research output: Contribution to journalArticlepeer-review

Abstract

Emissions of N2O and CH4 and CH4 oxidation rates were measured from Lolium perenne swards in a short-term study under ambient (36 Pa) and elevated (60 Pa) atmospheric CO2 at the Free Air Carbon dioxide Enrichment experiment, Eschikon, Switzerland. Elevated pCO2 increased (P<0.05) N2O emissions from high N fertilised (11.2gNm-2) swards by 69%, but had no significant effect on net emissions of CH4. Application of 13C-CH 4 (11 μl l-1; 11at.% excess 13C) to closed chamber headspaces in microplots enabled determination of rates of 13C-CH4 oxidation even when net CH4 fluxes from main plots were positive. We found a significant interaction between fertiliser application rate and atmospheric pCO2 on 13C-CH4 oxidation rates that was attributed to differences in gross nitrification rates and C and N availability. CH 4 oxidation was slower and thought to be temporarily inhibited in the high N ambient pCO2 sward. The most rapid CH4 oxidation of 14.6 μg 13C-CH4m-2h -1 was measured in the high fertilised elevated pCO2 sward, and we concluded that either elevated pCO2 had a stimulatory effect on CH4 oxidation or inhibition of oxidation following fertiliser application was lowered under elevated pCO2. Application of 14NH415NO3 and 15NH415NO3 (10at.% excess 15N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N2O emissions. Inhibition of CH4 oxidation in the high fertilised ambient pCO 2 sward, due to competition between NH3 and CH 4 for methane monooxygenase enzymes or toxic effects of NH 2OH or NO2- produced during nitrification, was hypothesised to increase gross nitrification (12.0mgNkgdry soil-1) and N2O emissions during nitrification (327 mg 15N-N 2Om-2 over 11d). Our results indicate that increasing atmospheric concentrations of CO2 may increase emissions of N 2O by denitrification, lower nitrification rates and either increase or decrease the ability of soil to act as a sink for atmospheric CH4 depending on fertiliser management.

Original languageEnglish
Pages (from-to)713-723
Number of pages11
JournalSoil Biology and Biochemistry
Volume36
Issue number4
DOIs
Publication statusPublished - 1 Apr 2004

Keywords

  • Atmospheric CO
  • Free Air Carbon dioxide Enrichment
  • Greenhouse gases
  • Lolium perenne
  • Methane oxidation
  • Nitrification
  • Nitrous oxide
  • Stable isotopes

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