Interference by magnesium in the determination of nitrate in 2 M KCl extracts of soil by steam distillation

Abstract

Steam distillation of 2 M KCl extracts of soil showed low recovery of NO₃‐N when compared with an automated method for NO₃‐N determination. The low recoveries were more pronounced in extracts where a soil:solution ratio of 1:2.5 had been used. In extracts where the Mg²⁺ content was in excess of 0.02 M Mg, recoveries of added NO₃‐N could be as low as 25%. Increasing the amount of Devarda's alloy or using a 1:10 soil:solution extraction ratio overcame the problem of low NO₃‐N recovery. Calcium salts did not interfere in the recovery of added NO₃‐N.