TY - JOUR
T1 - Accelerated diffusion methods for inorganic-nitrogen analysis of soil extracts and water
AU - Khan, S. A.
AU - Mulvaney, R. L.
AU - Mulvaney, C. S.
PY - 1997
Y1 - 1997
N2 - The major limitation of diffusion methods for N analysis is the lime required to obtain the results - typically from one to several days. Methods were developed that involve a much shorter period fur diffusion. In these methods, 10- to 100-mL samples of 2 or 4 M KCl soil extract or water were treated with MgO, or MgO plus Devarda's alloy, in a 473-mL (1-pint) wide-mouth Mason jar to liberate NH3-N4 NO3-N4 and/or NO2-N as NH3. The jar was placed on an electric griddle maintained at 45 to 50°C. Gaseous NH3 was collected in 5 mL of H3BO3 indicator solution in a petri dish attached to the Mason jar lid, for quantitative determination by acidimetric titration. Complete recovery of 4 mg of N was achieved from 10 or 20 mL in 1.5 to 5 h. Recovery from 50 or 100 mL was complete in 5 to 8.5 h with 1 to 2 mg of N. The methods permit 13N analysis of the diffused NH3-N. Isotopic analyses of labeled soil extracts were accurate to within 3%, as determined by isotope-dilution calculations. Diffusions from 10 to 50 mL were subject to very little, if any, interference from decomposition of alkali-labile organic-N compounds.
AB - The major limitation of diffusion methods for N analysis is the lime required to obtain the results - typically from one to several days. Methods were developed that involve a much shorter period fur diffusion. In these methods, 10- to 100-mL samples of 2 or 4 M KCl soil extract or water were treated with MgO, or MgO plus Devarda's alloy, in a 473-mL (1-pint) wide-mouth Mason jar to liberate NH3-N4 NO3-N4 and/or NO2-N as NH3. The jar was placed on an electric griddle maintained at 45 to 50°C. Gaseous NH3 was collected in 5 mL of H3BO3 indicator solution in a petri dish attached to the Mason jar lid, for quantitative determination by acidimetric titration. Complete recovery of 4 mg of N was achieved from 10 or 20 mL in 1.5 to 5 h. Recovery from 50 or 100 mL was complete in 5 to 8.5 h with 1 to 2 mg of N. The methods permit 13N analysis of the diffused NH3-N. Isotopic analyses of labeled soil extracts were accurate to within 3%, as determined by isotope-dilution calculations. Diffusions from 10 to 50 mL were subject to very little, if any, interference from decomposition of alkali-labile organic-N compounds.
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U2 - 10.2136/sssaj1997.03615995006100030032x
DO - 10.2136/sssaj1997.03615995006100030032x
M3 - Article
AN - SCOPUS:0031442887
SN - 0361-5995
VL - 61
SP - 936
EP - 942
JO - Soil Science Society of America Journal
JF - Soil Science Society of America Journal
IS - 3
ER -