Edaphic factors and plants influence denitrification in soils from a long-term arable experiment

Factors influencing production of greenhouse gases nitrous oxide (N(2)O) and nitrogen (N(2)) in arable soils include high nitrate, moisture and plants; we investigate how differences in the soil microbiome due to antecedent soil treatment additionally influence denitrification. Microbial communities, denitrification gene abundance and gas production in soils from tilled arable plots with contrasting fertilizer inputs (no N, mineral N, FYM) and regenerated woodland in the long-term Broadbalk field experiment were investigated. Soil was transferred to pots, kept bare or planted with wheat and after 6 weeks, transferred to sealed chambers with or without K(15)NO(3) fertilizer for 4 days; N(2)O and N(2) were measured daily. Concentrations of N(2)O were higher when fertilizer was added, lower in the presence of plants, whilst N(2) increased over time and with plants. Prior soil treatment but not exposure to N-fertiliser or plants during the experiment influenced denitrification gene (nirK, nirS, nosZI, nosZII) relative abundance. Under our experimental conditions, denitrification generated mostly N(2); N(2)O was around 2% of total gaseous N(2) + N(2)O. Prior long-term soil management influenced the soil microbiome and abundance of denitrification genes. The production of N(2)O was driven by nitrate availability and N(2) generation increased in the presence of plants.