Automated colorimetric determination of ammonium ions in soil extracts with ‘Technicon AutoAnalyzer II’ equipment

An automated method for the measurement of ammonium ions in Kjeldahl digests and 1M sodium chloride extracts of soils (for the determination of total nitrogen and cation exchange capacity respectively) is described. The method is based on the nitroprusside catalysed indophenol reaction, and using a ‘Technicon AutoAnalyzer II’ analysis rates of 100/h are possible. Results from 50 soils agreed well with results obtained by a standard distillation‐titration technique.