Effects of nitrification inhibitor and maize straw application on N2O and N2 emissions from two agricultural soils: A 15N tracer study

N 2 O and N 2 emissions from two soils after urea addition were quantified in the lab. The Inceptisol (alkaline) emitted much more N 2 O and N 2 than the Mollisol (acidic). NI application mitigated N 2 O emissions in both soils but differed on N 2 emission. Straw application mitigated N 2 O emissions in Mollisol but had little effects on N 2 emissions. The application of nitrification inhibitors (NIs) and crop straw with nitrogen (N) fertilizers is a common practice aimed at enhancing soil N conservation and improving crop N use. However, their effects on gaseous N emissions from soils, particularly for N 2 , are less understood. We conducted a 60-day soil incubation experiment under controlled conditions (80% water-filled pore space and 25°C) to investigate the effects of NI or maize straw application on N 2 O and N 2 emissions from two typical upland soils: a Mollisol and an Inceptisol, which have contrasting pH values. Both soils were fertilized with 15 N-labeled urea. During the incubation period, cumulative N 2 O and N 2 emissions for the urea-only treatment in the Mollisol were 0.5 and 12 mg N kg −1 soil, respectively, while emissions in the Inceptisol reached 15 and 176 mg N kg −1 . The application of NI (dicyandiamide) reduced N 2 O emissions by 66%–72% in both soils and decreased N 2 emissions by 81% in the Inceptisol, although it increased N 2 emissions by 15% in the Mollisol. Straw application also reduced N 2 O emissions by 60% in the Mollisol and by 4% in the Inceptisol, but it increased N 2 emissions by 75%–96% in both soils. Notably, the increased N 2 emissions following straw incorporation were primarily soil-derived rather than fertilizer-derived in both soils. These findings reveal that the applications of NIs or straw have varying impacts on N 2 O and N 2 emissions across different soils, and that NI application could be a promising strategy to reduce high gaseous N losses in Inceptisol following N fertilization.