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Eliminating Nitrate Interference During Kjeldahl Digestion of Soil Extracts for Microbial Biomass Determination
Author(s) -
Wyland L. J.,
Jackson L. E.,
Brooks P. D.
Publication year - 1994
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1994.03615995005800020016x
Subject(s) - kjeldahl method , chemistry , digestion (alchemy) , biomass (ecology) , environmental chemistry , nitrate , volatilisation , nitrogen , chromatography , agronomy , biology , organic chemistry
Nitrate interference in Kjeldahl digestion of soil and plant samples presents a significant problem in establishing N budgets in agricultural systems, where NO − 3 is frequently abundant. During digestion, NO − 3 can be reduced or it can cause volatilization of reduced N, resulting in either over‐ or under‐estimation of Kjeldahl N. A method has been developed to volatilize NO − 3 from K 2 SO 4 extracts of soil prior to Kjeldahl digestion for determination of microbial biomass N. Extracts were pretreated with H 2 O 2 and H 2 SO 4 at 97 °C for 48 h, and then were Kjeldahl digested using a procedure modified for microbial biomass extracts. This method volatilizes >99% of NO − 3 in K 2 SO 4 extracts, as determined by 15 N recovery from spiked samples.