Linking soil pH and phosphorus management to potential N2O emissions and nitrogen cycling microbial communities
Grau Butinyac, Meritxell
Grau Butinyac, Meritxell
Loading...
Identifiers
http://hdl.handle.net/10379/17270
https://doi.org/10.13025/17044
https://doi.org/10.13025/17044
Repository DOI
Publication Date
2022-08-15
Type
Thesis
Downloads
Citation
Abstract
Greenhouse gases (GHGs) in the atmosphere create the greenhouse gas effect, which allows maintenance of global temperatures. However, anthropogenic production of GHGs has caused dramatic increases of GHGs in the atmosphere, inducing global warming and resulting in substantial climatic changes. Mitigating GHGs emissions is thus a key priority to reduce the impact of climate change. Nitrous oxide (N2O) is a potent greenhouse gas that is not only involved in global warming but that also causes damage to the ozone layer. Soils are one of the major sources of N2O emissions. Excess application of nitrogen (N) on agricultural soils via synthetic fertiliser and manure can result in N losses due to leaching and N2O emissions. The N transformations that facilitate these losses are driven by soil microbial communities that respond to changes in their environment. These changes such as availability of inorganic N, soil pH and phosphorus (P) levels can be a consequence of agricultural management practices. Increases in soil pH have been linked to a reduction of N2O emissions through impacts on the microbial community at the functional and structural level, making pH management a possible approach for mitigating emissions. However, there is a need to assess whether the impact of pH on microbial communities involved in N transformations is conserved across a wide range of agronomic scenarios. Soil pH also affects P availability in the soil, creating an interaction effect of these soil properties that could also dictate both N2O emissions and microbial communities involved in the processes, but the role of P management, and of this interaction, on N2O production rates, and N cycling microbial communities, is poorly understood. The overall aim of this thesis was to investigate the impact of soil pH on microbial community structure and functional communities involved in N cycling processes, and to assess if this relationship was maintained across a geoclimatic gradient and a wide range of soil types. Also, this thesis aimed to investigate the long-term interaction between soil pH and P on these same N cycling microbial communities, and associated processes, to better understand their possible role in reducing N2O emissions from arable and grassland soils. This was achieved through qPCR quantification of functional, prokaryotic, and fungal communities, sequencing of prokaryotic and fungal communities, and laboratory incubations for the measurement of potential denitrification and nitrification. The abundance of denitrifier and nitrifier functional communities, and of prokaryotic and fungal communities were strongly impacted by both geoclimatic region (including soil type) and pH treatment. This effect of pH treatment was primarily positive on the abundance of the microbial communities present across pH treatments; however, the relationships present sometimes varied between sites and between sampling times within a site. Potential N2O emissions were influenced by pH treatment while potential nitrification rate was influenced by pH and P treatment interaction. This interaction effect was also observed on crenarchaea and denitrifier (nirK, nirS and nosZII) gene abundances. P treatment influenced fungal and nitrous oxide reductase (nosZI) gene abundances while pH treatment shaped the prokaryotic or fungal community structure. Overall, these results demonstrate microbial communities are shaped by agricultural management, with soil pH being a strong factor determining the functional and structural community, but also indicating P has a role in influencing these same processes and microbes. Understanding the response of microbial communities to management practices will be key for future mitigation of greenhouse gas N2O from agricultural soils and reducing the impact of agriculture on the environment.
Funder
Publisher
NUI Galway