Alternative Methods for Measuring Inorganic, Organic, and Total Dissolved Nitrogen in Soil
- Rebecca Hood-Nowotnya,
- Nina Hinko-Najera Umanab,
- Erich Inselbacherc,
- Petra Oswald- Lachouaniabc and
- Wolfgang Wanek *a
- a Dep. of Chemical Ecology and Ecosystem Research, Univ. of Vienna, Althanstrasse 14, 1090 Vienna, Austria
b Dep. of Forest and Ecosystem Science, Univ. of Melbourne, Water St., Creswick, VIC 3363, Australia
c Dep. of Forest Ecology and Management, Swedish Univ. of Agricultural Sciences, SE-901, 83 Umeå, Sweden
There are numerous methods for measuring inorganic, dissolved organic, and microbial N in soils, although many of these are complex or require expensive equipment. We have modified methods for the measurement of NH4 +, NO3 −, total dissolved N (TDN), and soil microbial biomass N (SMBN) in soils. The methods are based on a microtiter plate format and are rapid and simple to perform. Ammonium is quantified by a colorimetric method based on the Berthelot reaction. Total dissolved N and SMBN (by CH3Cl fumigation-extraction) are quantified as NO3 − after alkaline persulfate oxidation. Nitrate is estimated directly or after persulfate oxidation by reduction of NO3 − to NO2 − by VCl3 and subsequent colorimetric determination of NO2 − by acidic Griess reaction. The new suite of methods was compared with conventional methods such as high-performance anion-exchange chromatography for NO3 − and high-temperature catalytic oxidation for TDN. Our methods produced comparable detection limits, linearities, and precisions compared with the conventional methods. Limits of quantification were 7 μg NH4 +–N L−1, 55 μg NO3 −–N L−1, and 0.275 mg TDN L−1 The accuracy of the proposed methods was excellent, with recoveries of added NH4 +, NO3 −, and glycine ranging between 96 and 99%. Linearities of the respective calibrations were high (R 2 > 0.99), and precisions for NH4 + (CV = 2.1%), NO3 − (CV = 3.5%), and TDN (CV = 3.9%) were comparable to the reference methods. The simplicity, rapidity, and low cost of the proposed methods therefore allow an expansion of the scope and range of N cycle studies where sophisticated instrumentation is not available.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2010.