Dicyandiamide and 3,4-dimethyl pyrazole phosphate decrease N2O emissions from grassland but dicyandiamide produces deleterious effects in clover.

Summary The application of nitrogen fertilisers leads to different ecological problems such as nitrate leaching and the release of nitrogenous gases. N 2 O is a gas involved in global warming, therefore, agricultural soils can be regarded as a source of global warming. Soil N 2 O production comes from both the nitrification and denitrification processes. From an ecological viewpoint, using nitrification inhibitors with ammonium based fertilisers may be a potential management strategy to lower the fluxes of N 2 O, thus decreasing its undesirable effect. In this study, the nitrification inhibitors (NIs) dicyandiamide (DCD) and 3,4-dimethyl pyrazole phosphate (DMPP) have been evaluated as management tools to mitigate N 2 O emissions from mineral fertilisation and slurry application in grassland systems (experiments 1 and 2), and to assess the phytotoxic effect of these inhibitors per se on clover (experiment 3). Both nitrification inhibitors acted in maintaining soil nitrogen (N) in ammonium form, decreasing cumulative N 2 O emissions. DCD, but not DMPP, produced phytotoxic effects and yield reduction in white clover. A nutrient imbalance, which led to a senescence process visually observed as chlorosis and necrosis at the border of the leaves, was noted.