Determination of ammonia and nitrate in soil

Abstract

1. Methods for the determination of ammonia and nitrate in soil are described. The ammonia and nitrate are extracted at pH 1·0–1·5 with a mixture of potassium sulphate and sulphuric acid, and the ammonia is determined by distillation with magnesium oxide at 25° C. in a modified Conway microdiffusion unit. Ammonia plus nitrate is determined on a separate sample of the same extract by reduction of the nitrate to ammonia with titanous hydroxide and subsequent distillation with magnesium oxide, both the reduction and distillation being carried out in a modified microdiffusion unit at 25° C. 2. The methods are applicable to coloured extracts and are not affected by substances found to interfere with other methods of determining ammonia and nitrate. 3. It is suggested that the methods may also prove useful for the determination of ammonia and nitrate in plant materials.