Use of Diffusion for Automated Nitrogen-15 Analysis of Soil Extracts

Y. P. Liu, R. L. Mulvaney

Research output: Contribution to journalArticlepeer-review


Studies to evaluate the use of diffusion for automated I5N analysis of inorganic N in soil extracts showed that serious error can arise from use of the Devarda's alloy recommended for steam distillations and that the error can be avoided by using a commercial product of higher purity. These studies showed that serious error can also arise when NH3--N is diffused following NH4+-N and that separate diffusions should be performed for NH4+-N and (NH4++ N03-)-N. Other work demonstrated that the plastic specimen containers employed for diffusion can be reused if acid-washed, that diffusions can be performed using either light or heavy MgO without ignition to decompose carbonate, and that labeled N02- is completely removed from soil extracts by treatment with sulfamic acid before diffusion. A comparison of l5N analyses by steam distillation and diffusion using extracts from two soils revealed better agreement for the soil having a lower content of organic matter. Substantial differences in analyses by the two techniques for the soil having a higher organic-matter content were attributed to enzymatic conversions of inorganic N during the 6-d diffusion period.

Original languageEnglish (US)
Pages (from-to)613-629
Number of pages17
JournalCommunications in Soil Science and Plant Analysis
Issue number5-6
StatePublished - Mar 1 1992

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science


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