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There is an increasing concern about the negative impacts associated to the release of reactive nitrogen (N) from highly fertilized agro-ecosystems. Ammonia (NH) and nitrous oxide (NO) are harmful N pollutants that may contribute both directly and indirectly to global warming. Surface applied manure, urea and ammonium (NH) based fertilizers are important anthropogenic sources of these emissions. Nitrification inhibitors (NIs) have been proposed as a useful technological approach to reduce NO emission although they can lead to large NH losses due to increasing NH pool in soils. In this context, a field experiment was carried out in a maize field with aiming to simultaneously quantify NH volatilization and NO emission, assessing the effect of two NIs 3,4‑dimethilpyrazol phosphate (DMPP) and 3,4‑dimethylpyrazole succinic acid (DMPSA). The first treatment was pig slurry (PS) before seeding (50 kg N ha) and calcium ammonium nitrate (CAN) at top-dressing (150 kg N ha), and the second was DMPP diluted in PS (PS + DMPP) (50 kg N ha) and CAN + DMPSA (150 kg N ha) also before seeding and at top-dressing, respectively. Ammonia emissions were quantified by a micrometeorological method during 20 days after fertilization and NO emissions were assessed using manual static chambers during all crop period. The treatment with NIs was effective in reducing c. 30% cumulative NO losses. However, considering only direct NO emissions after second fertilization event, a significant reduction was not observed using CAN+DMPSA, probably because high WFPS of soil, driven by irrigation, favored denitrification. Cumulative NH losses were not significantly affected by NIs. Indeed, NH volatilization accounted 14% and 10% of N applied in PS + DMPP and PS plots, respectively and c. 2% of total N applied in CAN+DMPSA and CAN plots. Since important NH losses still exist even although abating strategies are implemented, structural and political initiatives are needed to face this issue.

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