prEN 18255

SLOVENSKI STANDARD
01-december-2025
Izboljševalci tal in rastni substrati - Določanje organskega dušika
Soil improvers and growing media - Determination of organic nitrogen
Bodenverbesserungsmittel und Kultursubstrate - Bestimmung von organischem
Stickstoff
Amendements du sol et supports de culture - Dosage de l’azote organique
Ta slovenski standard je istoveten z: prEN 18255
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080
English Version
Soil improvers and growing media - Determination of
organic nitrogen
Bodenverbesserungsmittel und Kultursubstrate -
Bestimmung von organischem Stickstoff
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 223.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18255:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Determination of Urea – nitrogen . 4
5.1 Principle . 4
5.2 Reagents and materials . 4
5.3 Apparatus . 5
5.4 Sampling . 5
5.5 Procedure . 5
6 Calculation and expression of the results . 6
7 Test report . 7
8 Validation of the method . 7
8.1 Validation in accordance with ISO 5725-2. 7
8.2 Performance characteristics. 7
Annex A (informative) Performance characteristics of the method . 8
Bibliography . 10

European foreword
This document (prEN 18255:2025) has been prepared by Technical Committee CEN/TC 223 “Soil
improvers and growing media”, the secretariat of which is held by NEN, in collaboration with CEN/TC 260
“Fertilizers and liming materials”.
This document is currently submitted to the CEN Enquiry.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
1 Scope
This document specifies a method for the determination of the organic nitrogen content in organic soil
improvers.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
CEN/TS 17732:2022, Soil improvers and growing media - Terminology
EN 12579:2024, Soil improvers and growing media - Sampling
prEN 13040-1:2025, Soil improvers and growing media — Sample preparation — Part 1: Sample
preparation for chemical and physical tests, determination of dry matter content, moisture content and
laboratory bulk density
prEN 13651:2025, Soil improvers and growing media — Extraction of calcium chloride/DTPA (CAT)
soluble nutrients and elements
prEN 13654-1:2025, Soil improvers and growing media — Determination of nitrogen — Part 1: Modified
Kjeldahl method
prEN 13654-2:2025, Soil improvers and growing media — Determination of nitrogen — Part 2: Dumas
method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 17732:2022 apply.
4 Principle
The content of organic nitrogen is calculated as the difference of the total nitrogen content and the
content of CAT extractable nitrogen calculated as the sum of ammonium nitrogen, nitrate nitrogen and
the urea nitrogen determined as described in this document.
5 Determination of Urea – nitrogen
5.1 Principle
The sample is extracted with water with the addition of a clarifying agent. The suspension is filtered. The
urea that has gone into solution is converted in the filtrate by the addition of 4-
dimethylaminobenzaldehyde (4-DMAB) into a urea-aldehyde condensation compound, the absorbance
of which is measured at 435 nm.
NOTE Additionally to the method described, other methods for the determination of urea nitrogen are possible,
e.g. CEN/TS 17771 or EN 15604.
5.2 Reagents and materials
5.2.1 Ethanol (C H OH), 96 %.
2 5
5.2.2 Hydrochloric acid (HCl) = 37 %; (HCl) = 1,19 g/ml.
5.2.3 4-(Dimethylamino)benzaldehyde (C H NO) (DMBA).
9 11
5.2.4 4-Dimethylaminobenzaldehyde solution: dissolve 1,6 g DMAB (5.2.3) in 100 ml ethanol (5.2.1)
and add 10 ml hydrochloric acid (5.2.2). The solution is stable for 2 weeks.
5.2.5 Zinc acetate dih
...