Ammonia-oxidation as an engine to generate nitrous oxide in an intensively managed calcareous Fluvo-aquic soil

We combine field observations, microcosm, stoichiometry, and molecular and stable isotope techniques to quantify N(2)O generation processes in an intensively managed low carbon calcareous fluvo-aquic soil. All the evidence points to ammonia oxidation and linked nitrifier denitrification (ND) being the major processes generating N(2)O. When NH(4)(+)-based fertilizers are applied the soil will produce high N(2)O peaks which are inhibited almost completely by adding nitrification inhibitors. During ammonia oxidation with high NH(4)(+) concentrations (>80 mg N kg(−1)) the soil matrix will actively consume oxygen and accumulate high concentrations of NO(2)(−), leading to suboxic conditions inducing ND. Calculated N(2)O isotopomer data show that nitrification and ND accounted for 35–53% and 44–58% of total N(2)O emissions, respectively. We propose that slowing down nitrification and avoiding high ammonium concentrations in the soil matrix are important measures to reduce N(2)O emissions per unit of NH(4)(+)-based N input from this type of intensively managed soil globally.