Dynamics of Nitrifier Gene Copy Numbers, Nitrogen Substrates and Nitrous Oxide Under Varying Rates of Urea Addition in Contrasting Soil Types.

We have been measuring the dynamics of gene copies associated with ammonia- (AOB) and nitrite-oxidizing bacteria (NOB) concurrently with measurement of soil N substrates (ammonium, nitrite, nitrate) and nitrous oxide (N₂O) dynamics in several different soil types following amendment with varying rates of urea fertilizer.  We observed clear differences among soils in their potential to produce N₂O and have related their inorganic N and N₂O production potential to differences in gene copy dynamics. We also report results of a recent study which showed how differences in ammonium sorption capacity among soils regulate solution-phase ammonia (NH₃) which in turn affects NH₃ inhibition of NOB. These dynamics were able to explain differences in N₂O production between soils.