Improved diffusion methods for determination of inorganic nitrogen in soil extracts and water

R. L. Mulvaney, S. A. Khan, W. B. Stevens, C. S. Mulvaney

Research output: Contribution to journalArticle

Abstract

Diffusion methods previously developed for inorganic-N analysis of soil extracts were modified to improve reliability, increase the dynamic range, extend the scope of applications, and simplify the processing of samples for N-isotope analysis. In these methods, the soil extract is treated with MgO, or MgO plus Devarda's alloy, in a 473-ml (1-pint) wide-mouth Mason jar to convert NH4/+-N, NO3/--N, and/or NO2/--N to NH3/--N. The NH3 thereby liberated is collected in H3BO3-indicator solution in a Petri dish suspended from the Mason-jar lid and determined quantitatively by acidimetric titration. With the modifications described, analyses can be performed on 10- to 100-ml samples of water, 0.5 M K2SO4, 1 M KCl, 2 M KCl, or 4 M KCl, at temperatures between 20 and 30°C. Recovery from 10 or 20 ml was quantitative in 18-80 h with up to 4 mg N: recovery from 50 or 100 ml was quantitative in 3-13 days with up to 2 mg N. Removal of H3BO3 for N-isotope analysis by the Rittenberg process was effected using methanol. Mason-jar diffusion methods are much simpler and more convenient than conventional steam distillations. Comparative studies showed that quantitative determinations are more accurate and precise by diffusion than by distillation.

Original languageEnglish (US)
Pages (from-to)413-420
Number of pages8
JournalBiology and Fertility of Soils
Volume24
Issue number4
DOIs
StatePublished - Jan 1 1997

Keywords

  • Ammonium analysis
  • Inorganic N
  • N
  • Nitrate
  • Nitrite
  • Soil extract diffusion method

ASJC Scopus subject areas

  • Microbiology
  • Agronomy and Crop Science
  • Soil Science

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