Alternative methods for measuring inorganic, organic, and total dissolved nitrogen in soil

Abstract

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 microliter plate format and are rapid and simple to perform. Ammonium is quantified by a colorimetric method based on the Benhelot reaction. Total dissolved N and SMBN (by CH3Cl fumigation-extraction) are quantified as NO 3- after alkaline persulfare oxidation. Nitrate is estimated directly or after persulfate oxidation by reduction of NO 3- to NO2- by VCl3 and subsequent col..