Automated Analysis of Nitrite, Nitrate, and Ammonium Nitrogen in Soils

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Abstract
Automated procedures are presented for determining NO‐2‐N, NO‐3‐N, and NH+4‐N in various soil testing programs. An AutoAnalyzer system equipped with a microprocessor‐based controller and data handler was employed in the study. The new system, through its drift, gain, and carryover correction features, provides improvement in accuracy and precision of results. Further, the new system also has the potential for more rapid chemical determination. The evaluation of accuracy and precision of NO‐3‐N and NH+4‐N analyses, studied in standard solutions and determined with the automated system at 60, 90, and 120 h−1 sampling rates, is presented. Results of NO‐2‐N, NO‐3‐N, and NH+4‐N analyses in nutrient solutions of hydroponic culture, as well as in extracts of mineral soils and peat‐based greenhouse substrates, determined with the automated procedure at the 90 h−1 sampling rate, are also presented. Moreover, the total N content and cation exchange capacity of mineral soils determined by NH+4‐N analysis with the AutoAnalyzer at the 90 h−1 sampling rate are also shown. Analyses performed by automated procedures are compared with those obtained by a nonautomated colorimeter for all samples used in the study. Nitrite nitrogen and NO‐3‐N were determined by hydrazine reduction, and NH+3‐N was determined as indophenol in both the automated and nonautomated procedures. Also, the threshold concentration levels of interfering ions determined in aqueous standard solutions of NO‐2‐N, NO‐3‐N, and NH+4‐N are presented.
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Funding Information
  • New Jersey Agric. Exp. Stn. (D-15117-1-84)

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