Denitrification in Lowbush Blueberry Soils

Effects of environmental variables on denitrification in acid (pH 4.0–5.5), infertile soils of lowbush blueberry (Vaccinium angustifolium Ait.) stands were investigated under laboratory conditions. All soils produced N 2 O when nitrate was added and samples were waterlogged and incubated for 2 d at temperatures of 20 °C or greater. No N 2 O production occurred at temperatures of 15 °C or lower. Nitrous oxide was the main gas evolved at the natural pH levels of these soils. Mercuric chloride inhibited nitrous oxide evolution. Raising soil pH resulted in increased rates of denitrification, and in more conversion of nitrous oxide to dinitrogen. Soil taken from a site that had been fertilized repeatedly exhibited higher rates of N 2 O evolution than did soil from a site that had never been fertilized. N 2 O production from waterlogged samples without added nitrate was positively correlated with percent organic matter and nitrate concentration of soils at the time of sampling. In a field experiment, more N 2 O was produced by samples from fertilized plots than by those from unfertilized plots, but absolute values from both types of plots were low.