FprEN 18255

• Abstract:

  This document specifies a method for the determination of the organic nitrogen content in soil improvers and growing media.; NOTE This method has been validated in an interlaboratory study with specific products that were present on the market during the study (as included in Annex A, being composted bark (20 mm to 40 mm), biowaste compost (Rottegrad 3), green compost (Rottegrad 5,0 mm to 15 mm), solid digestate and growing media blend 1: white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements))).

• Status: Not Published
• Publication Date: 06-Jan-2027
• ICS: 65.080 - Fertilizers
• Technical Committee: CEN/TC 223 - Soil improvers and growing media
• Drafting Committee: CEN/TC 223/WG 4 - Analytical methods
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Start Date: 28-Jul-2026
• Due Date: 12-Oct-2024
• Completion Date: 28-Jul-2026
• Directive: Not Harmonized2003/2003 - Regulation (EC) N° 2003/2003 of the European Parlament and of the council of 13 October 2003 relating to fertilisers
• Directive:

  ---

  Harmonized Standard2019/1009 - Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003 (Text with EEA relevance)
• Mandate: M/564 - Fertilising products in support of Regulation (EU) 2019/1009
• Mandate: M/564 AMD 1 - amending Implementing Decision C(2020) 612 as regards certain harmonised standards and standardisation deliverables, deadlines for their adoption and the duration of the validity of the standardisation request
• Mandate: M/564 AMD 2 - Commission Implementing decision amending Implementing Decision C(2020)612 as regards harmonised standards, the deadlines for the adoption of those standards and the duration of the validity of the standardisation request to the European Committee for Standardisation as regards the EU fertilising products in support of Regulation (EU) 2019/1009 of the European Parliament and of the Council
• Mandate: M/588 - COMMISSION IMPLEMENTING DECISION of 20.9.2022 on a standardisation request to the European Committee for Standardisation as regards methods for the measurements of emissions into the air of polychlorinated dibenzo-pdioxins and furans (PCDDs/PCDFs) and dioxin-like polychlorinated biphenyls (PCBs), total gaseous mercury and formaldehyde in support of Directive 2010/75/EU of the European Parliament and of the Council
• Mandate: M/XXX - M/XXX
• Ref Project: oSIST prEN 18255:2025 - Soil improvers and growing media - Determination of organic nitrogen

Overview

FprEN 18255 is a draft European standard developed by CEN that specifies a method for the determination of organic nitrogen content in soil improvers and growing media. Accurate measurement of organic nitrogen in these materials is essential for quality assurance within the agricultural, horticultural, and environmental industries. This method ensures reliable and reproducible results, supporting compliance with EU Fertilising Product Regulation (EU 2019/1009), and helps stakeholders optimize soil health and plant growth.

Key Topics

• Scope: Defines a standardized procedure for measuring the organic nitrogen in various soil improvers and growing media, including composted bark, biowaste compost, green compost, solid digestate, and blends containing peat, compost, wood fibre, and fertilizers.
• Principle: Organic nitrogen content is calculated by subtracting water-extractable (ammonium, nitrate, and urea) nitrogen forms from total nitrogen, using validated chemical procedures.
• Validation: The method was validated through interlaboratory studies across European laboratories, confirming its accuracy, repeatability, and reproducibility for a wide range of product types.
• Reporting: Ensures detailed and standardized reporting, including reference to the standard, sample identification, test results, sampling and analysis dates, and any deviations or incidents during the test.
• International Alignment: Developed in accordance with ISO 5725-2 for method validation and repeatability.

Applications

FprEN 18255 is valuable in several professional contexts:

• Quality Assurance for Producers: Manufacturers of soil improvers and growing media can use this standardized method to certify the organic nitrogen content of their products, supporting product claims and regulatory compliance.
• Environmental and Agricultural Laboratories: Soil and environmental labs can rely on this method to deliver standardized testing services to farmers, horticulturalists, and the wider agricultural sector.
• Regulatory Compliance: The method supports conformity assessment for trading and use of fertilisers and growing substrates within the European market, ensuring that products meet legal requirements for nutrient content.
• Research and Development: Research organizations can apply the method for product development and scientific studies on soil and substrate improvement, plant nutrition, and sustainable resource use.

Related Standards

For effective application and broader understanding, the following related standards and documents should also be considered:

• EN 12579:2024 – Soil improvers and growing media - Sampling: For ensuring representative sample collection.
• prEN 13040-1:2025 – Soil improvers and growing media - Sample preparation: Operational procedures for preparing samples for analysis.
• prEN 13651:2025 – Extraction of calcium chloride/DTPA (CAT) soluble nutrients and elements: Related to the extraction of nitrogen forms.
• prEN 13654-1 & 2:2025 – Determination of nitrogen (Kjeldahl and Dumas methods): Methods for total nitrogen determination.
• CEN/TS 17732:2022 – Terminology for soil improvers and growing media.
• EN 15604, CEN/TS 17771 – Additional nitrogen determination methods.
• ISO 5725-2 – Validation of measurement methods (repeatability and reproducibility).
• Regulation (EU) 2019/1009 – European Fertilising Product Regulation.

By adhering to FprEN 18255 and these related standards, professionals across the soil, fertiliser, and environmental sectors can ensure accurate, consistent, and regulatory-compliant determination of organic nitrogen in vital growing media and soil improvers. This promotes product quality, sustainability, and confidence in agricultural and environmental management practices.

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
prEN 18255
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.

prEN 18255:2025 (E)
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

prEN 18255:2025 (E)
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.
prEN 18255:2025 (E)
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.
prEN 18255:2025 (E)
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
...