ISO INTERNATIONAL STANDARD 14255 First edition 1998-05-01 Soil quality Determination of nitrate nitrogen, ammonium nitrogen and total soluble nitrogen in air-dry soils using calcium chloride solution as extractant Qualité du sol - Détermination de I'azote nitrique, de I'azote ammoniacal et de I'azote soluble total dans les sols séchés a I'air en utilisant le chlorure de calcium comme solution d'extraction ISO Referencenumber ISO 14255:1998(E) y IHS under ted without license from IHS Not for Resale ISO 14255:1998(E) Foreword IsO (the International Organization for Standardization) is a worldwide federationofnationalstandardsbodies(lsOmemberbodies).Theworkof preparing International Standards is normally carried out through isO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non- governmental, in liaison with ISO, also take part in the work. IsO collaborates closely with the International Electrotechnical Commission (lEC)onallmattersofelectrotechnicalstandardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 14255 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical methods and soil characteristics. Annexes A and B of this International Standard are for information only. @ISO1998 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced microfilm, without permission in writing from the publisher. InternationalOrganizationforStandardization Case postale 56· CH-1211 Geneve 20 · Switzerland Internet [email protected] X.400 C=ch; a=400net; p=iso; 0=isocs; S=central Printed in Switzerland it license from IHS Not for Resale ISO 14255:1998(E) INTERNATIONAL STANDARD @ISO Soil quality Determination of nitrate nitrogen, ammonium nitrogen and total soluble nitrogen in air-dry soils using calcium chloride solution as extractant 1 Scope This International Standard describes a method for the determination of soluble nitrogen fractions (nitrate, nitrite, ammonium and organic nitrogen) in a 0,01 mol/l calcium chloride extract of soil samples. It is applicable to air-dry soil samples, pretreated in accordance with IsO 11464. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to possibility of applying the most recent editions of the standards indicated below. Members of IEC and isO maintain registers of currently valid International Standards. IsO 3696:1987, Water for analytical laboratory use — Specification and test methods. Iso 11464:1994, Soil quality — Pretreatment of samples for physico-chemical analyses. Iso 11465:1993, Determination of dry matter and water content on a mass basis - Gravimetric method. 3 Principle By means of a simple extraction with a 0,01 mol/l calcium chloride (CaCl2) solution of air-dry soil samples, different solublenitrogenfractionsare extracted(seereferences[1land[2l).Theconcentrationsofthe inorganicnitrogen methods. is converted to nitrate. This, together with the originally present nitrate (+ nitrite) and ammonia, is then measured using an automated spectrometric method. The content of soluble organic nitrogen is calculated by subtracting the content of nitrate (+ nitrite) and ammonium nitrogen from the content of soluble total nitrogen. NOTES The content of soluble organic nitrogen may give an indication of the easily mineralizable fraction of the organic matter. 2 The content of extractable ammonium and organic nitrogen of the soil is changed very often by drying, compared to