Nitrous oxide cumulative emission from soil under different nitrogen sources over three years of maize cultivation in Southern Brazil

The agricultural sector accounts for 30% of Brazilian greenhouse gas emissions, including 76% of nitrous oxide (N₂O) emissions. Therefore, the sustainable use of nitrogen(N) fertilizers is crucial for reducing N₂O emissions and maintaining production sustainability. The objective was to evaluate the use of N fertilizers in maize over three agricultural seasons (2022-23, 2023-24, 2024-25) on soil N₂O losses in a Brazilian Subtropical Oxisol. The treatments were control (C), ammonium nitrate (AN), ammonium nitrate with 70% rate (AN70), urea (UR), and urea with urease inhibitor (UR+NBPT). The N was applied in maize with a rate of 180 kg ha^-1. Soil N₂O fluxes were evaluated over approximately 100 days in each maize cultivation (agricultural season: September to January) by the closed static chamber method, with the determination of N₂O cumulative emission and N₂O emission factor. On average of all agricultural seasons, UR showed the highest N₂O cumulative emission (0.79 kg N-N₂O ha^-1), similar to UR+NBPT (0.65 kg N-N₂O ha^-1), but differing from AN70 (0.58 kg N-N₂O ha^-1), AN (0.46 kg N-N₂O ha^-1), and C (0.28 kg N-N₂O ha^-1), by Tukey’s test, p>0.10. The UR also presented the highest N₂O emission factor (0.28%), similar to UR+NBPT (0.20%), and differing from AN70 (0.16%) and AN (0.10%) (Tukey’s test, p>0.10); however, the values were below the IPCC reference value of 1.6%. In conclusion, the use of ammonium nitrate in maize under no-tillage is an efficient alternative to mitigating N₂O emission from a Brazilian Subtropical Oxisol.