Evaluation of methods for nitrogen-15 analysis of inorganic nitrogen in soil extracts. il diffusion methods

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

Research output: Contribution to journalArticlepeer-review

Abstract

Diffusion of inorganic nitrogen (N) onto acidified filters is a rapid method of preparing soil extracts for 15N analysis by automated mass spectrometers (ANCA-MS); however, recent studies indicate variable recovery of 15N added labels from some soils. A study was conducted to evaluate this method for recovery of N and 15N by diffusion of 2 M KC1 extracts from 10 diverse soils. The extracts were treated with: (i) (l5NH4)2S04 and KN03, (ii) (NH4)2S04 and K15N03, or (iii) KN03 and Na15N02. Diffusions of ammonium-nitrogen (NH/-N) and nitrate-nitrogen (N03‘-N) were either done sequentially or combined; a sulfamic acid pretreatment was employed for diffusion of N03‘-N in the presence of N02-N. Nitrogen-15 analyses of diffused NH4+-N by ANCA-MS yielded 99 to 100% recovery. The range for diffused N03‘-N was 97 to 102%, using a surfactant to improve recovery and minimize variance. Isotopic carryover of NH4+ into N03’ diffusions was observed to occur, but could be minimized with pretreatment and analytical calibrations.

Original languageEnglish (US)
Pages (from-to)1675-1685
Number of pages11
JournalCommunications in Soil Science and Plant Analysis
Volume26
Issue number11-12
DOIs
StatePublished - Jun 1 1995

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science

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