Simultaneous determination of soil aluminum, ammonium‐ and nitrate‐nitrogen using 1 M potassium chloride extraction

Abstract Determination of soil aluminum (Al), ammonium‐nitrogen (NH4‐N), and nitrate‐nitrogen (NO3‐N) is often needed from the same soil samples for lime and fertilizer recommendations, but Al has to be extracted and quantified separately from NH4‐N and NO3‐N according to present methods. The objective of this study was to develop a reliable method for simultaneous analyses of soil Al, NH4‐N and NO3‐N using a Flow Injection Autoanalyzer. Thirty‐five soil samples from different locations with wide ranges of extractable Al, NH4‐N and NO3‐N were selected for this study. Aluminum, NH4‐N and NO3‐N were extracted by both 1 M and 2 M potassium chloride (KCl), and quantified using a LACHAT Flow Injection Autoanalyzer simultaneously and separately. One molar KCl was found to be a suitable extractant for all three compounds when compared to 2 M KCl. The 1 M KCl extract proposed could aid in decreasing the costs associated with simultaneous NH4‐N, NO3‐N, and Al analyses. Results of those three compounds analyzed simultaneously were not statistically different from those analyzed separately in 1 M KCl solution. This new procedure of simultaneous determination of NH4‐N, NO3‐N, and Al increases efficiency and reduces cost for soil test laboratories and laboratory users.