Evaluation of methods for nitrogen-15 analysis of inorganic nitrogen in soil extracts: I. Steam-distillation methods

R. L. Mulvaney, M. Ashral, F. Azam, P. D. Brooks, D. J. Herman

Research output: Contribution to journalArticlepeer-review

Abstract

A study was conducted to evaluate conventional steam-distillation techniques for N-isotope analysis of inorganic forms of N in soil extracts. Extracts obtained with 2 M KC1 from 10 diverse soils were treated with: (i) (15NH4)2SO4and KNO3, (ii) (NH4)2SO4and K15NO3, or (iii) KNO3and Na15NO2. Steam distillations were performed sequentially to determine NH4 +-N and NO3 --N, and were also carried out to determine (NOa -+ NO2-)-N or (NH4 + + NO3- + NO2')-N; a pretreatment with sulfamic acid was used to determine NO3 --N in the presence of NO2 --N. Recovery of added N ranged from 95 to 102%. Significant isotopic contamination was observed in sequential distillation of unlabeled NO3 --N following labeled NH4 +-N; otherwise, analyses for 15N were usually within 1% of the values calculated by isotope-dilution equations.

Original languageEnglish (US)
Pages (from-to)2187-2200
Number of pages14
JournalCommunications in Soil Science and Plant Analysis
Volume25
Issue number11-12
DOIs
StatePublished - Jul 1 1994

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science

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