Soil N Losses by Denitrification Evaluated Using the ¹⁵N Tracer Method

ABSTRACT

Molecular nitrogen (N₂) and nitrous oxide (N₂O) generated by denitrification increase N losses in the soil–plant system. This study aimed to quantify N₂ and N₂O from potassium nitrate (K¹⁵NO₃) applied to soils with different textures and moisture contents in the absence and presence of a source of carbon (C) using the ¹⁵N tracer method. In the three soils used (sandy texture (ST), sandy clay loam texture (SCLT), and clayey texture (CT)), three moisture contents were evaluated (40%, 60%, and 80% of the water holding capacity (WHC)) with (D⁺) and without (D⁻) dextrose added. The treatments received 100 mg N kg⁻¹ (KNO₃ with 23.24 atom% ¹⁵N). N₂ emissions occurred in all of the treatments, but N₂O emissions only occurred in the D⁺ treatment, showing increases with increasing moisture content. SCLT with 80% WHC in the D⁺ treatment exhibited the highest accumulated N emission (48.26 mg kg⁻¹). The ¹⁵N balance suggested trapping of the gases in the soil.

KEYWORDS:

• ¹⁵N balance
• isotope ratio mass spectrometry
• N₂
• N₂O

Acknowledgments

We thank Laboratório de Isótopos Estáveis do Centro de Energia Nuclear na Agricultura (CENA/USP) for the technical support.

Funding

We are thankful to FAPESP for the financial support (Project Number 2013/08980-4).

Additional information

Funding

We are thankful to FAPESP for the financial support (Project Number 2013/08980-4).