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Abstract A method is described for the direct estimation of NH+ 4‐N in 2M KCl extracts of soils based on the emerald green color formed when NH3 and salicylate react in the presence of NaOCl at high pH.‐The reagent concentration, solution pH, and time and temperature of color development specified are those giving maximum molar asorptivity. Precipitate formation observed when KCl extracts containing divalent cations were treated with color developing reagents was eliminated by addition of 1 mL of 6% EDTA to complex Ca2+ and Mg2+. Free EDTA or complexed Ca2+ or Mg2+ did not markedly affect color development or molar absorptivity. The proposed method efficiently recovered NH+ 4‐N added to 2M KCl extracts of soils and studies showed that the proposed method and two other procedures differing in principle gave similar values for NH+ 4‐N in extracts of 5 soils. The proposed method is a simple, rapid, accurate, and precise technique for the colorimetric determination of NH+ 4‐N in KCl extracts of soils.
Darreil W. Nelson (1983) studied this question.