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Biology and Fertility of Soils

, Volume 24, Issue 4, pp 413–420 | Cite as

Improved diffusion methods for determination of inorganic nitrogen in soil extracts and water

  • R. L. Mulvaney
  • S. A. Khan
  • W. B. Stevens
  • C. S. Mulvaney
ORIGINAL PAPER

Abstract

Diffusion methods previously developed for inorganic-N analysis of soil extracts were modified to improve reliability, increase the dynamic range, extend the scope of applications, and simplify the processing of samples for N-isotope analysis. In these methods, the soil extract is treated with MgO, or MgO plus Devarda‘s alloy, in a 473-ml (1-pint) wide-mouth Mason jar to convert NH4+-N, NO3-N, and/or NO2-N to NH3-N. The NH3 thereby liberated is collected in H3BO3-indicator solution in a Petri dish suspended from the Mason-jar lid and determined quantitatively by acidimetric titration. With the modifications described, analyses can be performed on 10- to 100-ml samples of water, 0.5MK2SO4, 1MKCl, 2MKCl, or 4MKCl, at temperatures between 20 and 30°C. Recovery from 10 or 20ml was quantitative in 18–80h with up to 4mgN; recovery from 50 or 100ml was quantitative in 3–13 days with up to 2mgN. Removal of H3BO3 for N-isotope analysis by the Rittenberg process was effected using methanol. Mason-jar diffusion methods are much simpler and more convenient than conventional steam distillations. Comparative studies showed that quantitative determinations are more accurate and precise by diffusion than by distillation.

Key words Ammonium analysis 15N Nitrate Nitrite Inorganic N Soil extract diffusion method 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • R. L. Mulvaney
    • 1
  • S. A. Khan
    • 1
  • W. B. Stevens
    • 2
  • C. S. Mulvaney
    • 3
  1. 1.Department of Natural Resources and Environmental Sciences, Turner Hall, University of Illinois, 1102 South Goodwin Avenue, Urbana, IL 61801, USAUS
  2. 2.Department of Crop Sciences, University of Illinois, Urbana, IL 61801, USAUS
  3. 3.426 North Fisler Road, Monticello, IL 61856, USAUS

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