Modification of the Cataldo method for the determination of nitrate in soil extracts by potassium chloride

The simple and sensitive colorimetric method developed by Cataldo et al, fo r the determination of nitrate in solution was modified to apply it for 2 M KCl soil extracts. The color intensity was decreased markedly when the KCl concentration of the sample solution increased, in contrast, the sensitivi ty was improved when the ratio of mixing volume of the sample and salicylic acid-sulfuric acid reagent was changed, and when the sample volume was inc reased. The modified method showed almost the same accuracy as the steam di stillation method with MgO and Devarda alloy.