Emissions of N2O from tropical forest soils: Response to fertilization with NH4+, NO3−, and PO43−

Undisturbed oxisols in a central Amazon tropical forest were fertilized with ammonium, nitrate, or phosphate. Enhanced emissions of N 2 O were observed for all treatments within 1 day of fertilization, with the response NO 3 − ≫NH 4 + ≫PO 4 3− . Approximately, 0.5% of applied NO 3 − was converted to N 2 O within 2 weeks after application, with less than 0.1% of the NH 4 + converted to N 2 O. These experiments reveal a potentially large source of N 2 O from microbial reduction of NO 3 − in the clay soils of Amazonia.