Molecular gene markers for nitrification and denitrification and comparison with agricultural soil nitrous oxide emissions

Nitrous oxide (N2O) is an important greenhouse gas that accounts for 6% of total global forcing. Soils produce 70% of yearly global emissions and arable agriculture contributes significantly to this. Most N2O production is from microbial activity and soil microbes produce N2O from two main pathways, nitrification and denitrification. It is important to understand the relationship between N2O production and its microbial origins under different crop regimes for better mitigation of N2O emissions in arable agriculture. Due to the phylogenetic spread of nitrifiers and denitrifiers, a functional gene approach is preferable for studying the microbial origins of these processes.
Open gas chamber sampling was carried out on open-bottomed soil cores filled with agricultural soils. Cores were either unplanted or filled planted with either Triticum aestivum or Brassica napus. Nitrogen was added as urea solution to some of the cores to simulate fertilizer addition. Soil-atmosphere fluxes of N2O were quantified and soil samples were taken for DNA extractions and analysis of the functional genes.
Flux data suggested evidence for differences in N2O emissions between T. aestivum and B. napus. N2O fluxes were significantly lower in cores planted with T. aesitivum compared to unplanted and B. napus cores when treated with nitrogen. There was no significant difference in presence of functional genes with nitrogen addition or between different planting regimes. This study found that different crops respond differently to N addition, causing significant changes in N2O emissions. It offers an additional tool to make decisions about soil and agricultural management, such as N addition and will enable more sustainable use of soils.