Nitrogen fertilizers promote denitrification

R. L. Mulvaney, S. A. Khan, C. S. Mulvaney

Research output: Contribution to journalArticlepeer-review


A laboratory study was conducted to compare the effects of different N fertilizers on emission of N2 and N2O during denitrification of NO3 in waterlogged soil. Field-moist samples of Drummer silty clay loam soil (fine-silty, mixed, mesic Typic Haplaquoll) were incubated under aerobic conditions for 0, 2, 4, 7, 14, 21, or 42 days with or without addition of unlabelled (NH4)2SO4, urea, NH4H2PO4, (NH4)2HPO4, NH4NO3 (200 or 1000 mg N kg-1 soil), or liquid anhydrous NH3 (1000 mg N kg-1 soil). The incubated soil samples were then treated with 15N-labelled KNO3 (250 mg N kg-1 soil, 73.7 atom% 15N), and incubation was carried out under waterlogged conditions for 5 days, followed by collection of atmospheric samples for 15N analyses to determine labelled N2 and N2O. Compared to samples incubated without addition of unlabelled N, all of the fertilizers promoted denitrification of 15NO3/-. Emission of labelled N2 and N2O decreased in the order: Anhydrous NH3>urea>>(NH4)2HPO4>(NH4)2SO4≃NH4NO3≃NH4H2PO4. The highest emissions observed with anhydrous NH3 or urea coincided with the presence of NO2 and 15N analyses indicated that these emissions originated from NO2/- rather than NO3/-. Emissions of labelled N2 and N2O were significantly correlated with fertilizer effects on soil pH and water-soluble organic C.

Original languageEnglish (US)
Pages (from-to)211-220
Number of pages10
JournalBiology and Fertility of Soils
Issue number2
StatePublished - Feb 1997


  • Denitrification
  • Fertilizer efficiency
  • Labelled dinitrogen
  • N
  • Nitrification
  • Nitrous oxide
  • Urea
  • Water-soluble organic carbon
  • Waterlogged soil

ASJC Scopus subject areas

  • Microbiology
  • Agronomy and Crop Science
  • Soil Science


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