Automated methods for ammonium, nitrate, and nitrite in 2MKCl‐phenylmercuric acetate extracts of soil

Automated methods for determining ammonium, nitrate, and nitrite in a single soil extract containing 2 M KCl and 5 mg/L phenylmercuric acetate are presented. The ammonium method is also suitable for Kjeldahl, soil and plant digests. Amino acid interferences with the ammonium method are reported. Ammonium is determined by a salicylate‐isocyanurate method, while nitrite is determined by the colorimetric reaction of N‐(l‐naphthyl)‐ethylenediamine dihydrochloride with sulfanilamide. Nitrate is determined in the same manner as nitrite after the sample has been passed through a Cu2+/Cd reduction column. The difference between the Cu2+/Cd reduced sample and nitrite sample value is nitrate.