Dimethylpyrazole-based nitrification inhibitors have a dual role in NO emissions mitigation in forage systems under Atlantic climate conditions.

Nitrogen fertilization is the most important factor increasing nitrous oxide (NO) emissions from agriculture, which is a powerful greenhouse gas. These emissions are mainly produced by the soil microbial processes of nitrification and denitrification, and the application of nitrification inhibitors (NIs) together with an ammonium-based fertilizer has been proved as an efficient way to decrease them. In this work the NIs dimethylpyrazole phosphate (DMPP) and dimethylpyrazole succinic acid (DMPSA) were evaluated in a temperate grassland under environmental changing field conditions in terms of their efficiency reducing NO emissions and their effect on the amount of nitrifying and denitrifying bacterial populations responsible of these emissions. The stimulation of nitrifying bacteria induced by the application of ammonium sulphate as fertilizer was efficiently avoided by the application of both DMPP and DMPSA whatever the soil water content. The denitrifying bacteria population capable of reducing NO up to N was also enhanced by both NIs provided that sufficiently high soil water conditions and low nitrate content were occurring. Therefore, both NIs showed the capacity to promote the denitrification process up to N as a mechanism to mitigate NO emissions. DMPSA proved to be a promising NI, since it showed a more significant effect than DMPP in decreasing NO emissions and increasing ryegrass yield.