Year: 2016
Type: dissertation
Abstract: Biochar amendment of soil has been found to have positive effects on soil physical properties and it has phenomenal C-sequestration potential.Moreover, there is evidence that it impacts the N-cycle as it changes the nitrification and denitrification dynamics in soil.These changes in turn could affect the N 2 O emissions.This is particularly important as N 2 O is a climate relevant greenhouse gas with approximately 300-times the global warming potential of CO 2 .Understanding the dynamics of N 2 O production in soil and its adaptations due to the incorporation of biochar is crucial if we are to effectively manage this important climate combating resource.Stable isotope techniques using 15 N and 18 O were recently found to be essential in determining these N 2 O dynamics and new laser based cavity ring down spectrometric (CRDS) methods have become available, which allow us to investigate the N 2 O sources in a laboratory setting.This enables us to systematically investigate the different processes behind N 2 O production.Therefore, in a laboratory based experiment we investigated the sources of N 2 O emissions using soils from a field experiment where biochar had been incorporated five years prior to the laboratory experiment.Soil samples of different biochar treatments (24 t ha -1 and 72 t ha -1 biochar addition with 120 kg ha -1 N-fertilizer) were analysed by stable isotope analysis.Isotope ratio mass spectrometry (IRMS) was performed on 15 N labelled soil samples and N 2 O fluxes were measured with a LGR (CRDS) Isotopic N 2 O Analyzer.In this study, there were no significant differences in the nitrous oxide fluxes, nitrification rates and N turnover rates between the biochar treatments and our control plots.This suggests that five years after biochar application, there was no significant effect of biochar on the mechanisms underpinning N 2 O emissions in this arable soil.Moreover, gross nitrification rates observed were higher than net nitrification rates suggesting large dinitrogen losses from the system.However, the proportion of N 2 O derived from denitrification was found to be substantially lower than the N 2 O emissions from nitrification, which could imply efficient denitrification under aerobic soil conditions.These results again highlight the importance of studying all possible N loss mechanisms to gain a full understanding of N dynamics under new management systems.Due to the very limited amount of long-term studies on biochar correlation to N 2 O emissions, more research is needed on its effects.
Author: Grabenhofer, Jutta
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDGs: Climate action, Life on land
Open Access status: green
OpenAlex ID: W6992640706