Controlling organic interference in determination of soil mineral nitrogen

Vander L.N. Nunes, Richard L. Mulvaney

Research output: Contribution to journalArticlepeer-review


Inorganic nitrogen (N) in the form of exchangeable ammonium (NH4+), nitrate (NO3), or nitrite (NO2) is normally extracted by shaking soil with a neutral salt solution and is subject to interference by soluble organic N (SON). After optimizing sequential diffusion methods to expedite recovery of NH4+–N and (NO3 + NO2)-N, 15N-tracer studies were conducted to ascertain whether extraction is quantitative when performed on soils amended with 2 g 15N kg−1 using 0.2, 1, and 2 M potassium chloride (KCl) and can be carried out by a simple leaching method instead of conventional shaking-filtration. The results verified a significant decrease in SON interference with the optimized diffusion procedures and showed that (a) interference is more serious for NH4+–N than for (NO3 + NO2)-N, (b) 2 M KCl is required for quantitative recovery of 15NH4+–N, and (c) leaching virtually eliminates organic interference during diffusion of (NO3 + NO2)-N. The leaching-diffusion approach minimizes the inflating effect of SON on soil inorganic N analyses and will be especially useful in N isotope studies.

Original languageEnglish (US)
Pages (from-to)919-928
Number of pages10
JournalSoil Science Society of America Journal
Issue number3
StatePublished - May 1 2021

ASJC Scopus subject areas

  • Soil Science


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