Determination of Nitrogen by Microdiffusion in Mason Jars: II. Inorganic Nitrogen-15 in Soil Extracts

N. S. Saghir, F. P. Mungwari, R. L. Mulvaney, F. Azam

Research output: Contribution to journalArticlepeer-review

Abstract

Simple microdiffusion methods were evaluated for N-isotope analysis of NH4 +, NO3 - and NO2 - in soil extracts. In these methods, the soil extract is treated with MgO or MgO and Devarda's alloy in a 473-mL (1-pint) widemouth Mason jar, the NH3 liberated being collected in a Petri dish containing 3 mL of boric acid-indicator solution, or in an acidified glass-fiber disk, suspended from the Mason-jar lid. To avoid cross-contamination error from retention of 15N, the lid was immersed in 0.05 M KOH for at least 24 h before reuse. Serious error occurred when NO3 --N was diffused following NH4 +-N; therefore, separate diffusions should be performed for NH4 +-N and (NH4 + + NO3 _)-N or (NH4 + + NO3 - +NO2 - )-N. In studies to evaluate the latter approach using labeled soil extracts analyses for 15N were within 2% of the corresponding values calculated by isotope-dilution equations. No interference by alkali-labile organic N was observed in diffusion of 15N-labeled extracts from soil receiving various treatments to increase soluble organic N.

Original languageEnglish (US)
Pages (from-to)2747-2763
Number of pages17
JournalCommunications in Soil Science and Plant Analysis
Volume24
Issue number19-20
DOIs
StatePublished - Dec 1 1993

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science

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