The effect of nitrification inhibitors on nitrous oxide emissions from cattle urine depositions to grassland under summer conditions in the UK

Abstract Nitrous oxide (N 2 O) has become the prime ozone depleting atmospheric emission and the third most important anthropogenic greenhouse gas, with a global warming potential approximately 300 times higher than CO 2 . Nitrification and denitrification are processes responsible for N 2 O emission from the soil after nitrogen input. The application of a nitrification inhibitor can reduce N 2 O emissions from these processes. The objective of this study was to assess the effect of two different nitrification inhibitors (dicyandiamide (DCD) and a commercial formulation containing two pyrazole derivatives (PD), 1H-1,2,4-triazole and 3-methylpyrazole) on N 2 O emissions from cattle urine applications for summer grazing conditions in the UK. Experiments were conducted under controlled conditions in a laboratory incubator and under field conditions on a grassland soil. The N 2 O emissions showed similar temporal dynamics in both experiments. DCD concentration in the soil showed an exponential degradation during the experiment, with a half-life of the order of only 10 d (air temperature c. 15 °C). DCD (10 kg ha −1 ) and PD at the highest application rate (3.76 kg ha −1 ) reduced N 2 O emissions by 13% and 29% in the incubation experiment and by 33% and 6% in the field experiment, respectively, although these reductions were not statistically significant ( P  > 0.05). Under UK summer grazing conditions, these nitrification inhibitors appear to be less effective at reducing N 2 O emissions than reported for other conditions elsewhere in the literature, presumably due to the higher soil temperature.