510 EXTRACTABLE NITRATE AND AMMONIUM IN BOTANICAL MATERIALS - DIFFUSION-CONDUCTIVITY ANALYZER METHOD
NO3-N, NH4-N
Total extractable nitrate and ammonium by 2% acetic acid extraction. Nitrate: Quantitative determination by zinc reduction and conductimetric analysis. Ammonium: Quantitative determination by conductimetric analysis.
Summary: 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 access plant overall nitrogen status and are correlated to plant response to nitrogen fertilization. Generally the method has a quantitative detection limit of 10 mg kg-1 (dry basis) and is generally reproducible within 8%.
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.