This method quantitatively extracts soluble nitrate (NO3-N) and ammonium (NH4-N) in botanical materials based on an extraction with a solution of 2% acetic acid. Ammonium is determined by the diffusion-conductivity method based on the gaseous diffusing of ammonia (NH3) across a gas permeable membrane in the presence of excess base (KOH) and subsequent conductivity detection. Nitrate is determined by first reducing it to ammonium using a copper-zinc reduction column and subsequent measurement as described above. Concentrations of these nutrients are used to assess plant overall nitrogen status and are correlated to plant response to nitrogen fertilization. The method detection limit is 10 ppm (dry basis).
High concentrations of ammonium can interfere with the nitrate quantitation. Volatile amines such as methylamine and ethylamine will interfere.
Sample amount requested: 3 g
Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.
Carlson, R. M., Cabrera, R. I., Paul, J. L., Quick, J. and Evans, R. Y. 1990. Rapid direct determination of ammonium and nitrate in soil and plant tissue extracts. Commun. Soil Sci. Plant Anal. 21:1519-1529.