FprEN 13654-1
(Main)Soil improvers and growing media - Determination of nitrogen - Part 1: Modified Kjeldahl method
- Abstract
This document specifies a method for the determination of nitrogen in soil improvers and growing media. The Kjeldahl method determines ammonium-N, nitrate-N, nitrite-N and organic N content of soil improvers and growing media. Nitrogen in N-N-linkages, N-O-linkages and some heterocyclics (especially pyridine) is only partially determined [6], [7], [8].
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, liquid digestate, soil improver (pellets, sieved 4 mm, growing media blend 1 (white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements)), growing media blend 2 (white peat, black peat, expanded perlite, lime, organic fertilizer) and growing media blend 3 (white peat, black peat, clay, inorganic fertilizer (NPK + micro elements))).
- Status
- Not Published
- Publication Date
- 13-Jan-2027
- Technical Committee
- CEN/TC 223 - Soil improvers and growing media
- Drafting Committee
- CEN/TC 223/WG 4 - Analytical methods
- Current Stage
- 5020 - Submission to Vote - Formal Approval
- Start Date
- 24-Sep-2026
- Due Date
- 21-Dec-2024
- Completion Date
- 24-Sep-2026
- Mandate
- M/XXX - M/XXX
FprEN 13654-1 is a CEN draft European Standard for determining nitrogen in soil improvers and growing media by a modified Kjeldahl method. It is written for laboratories that need to measure ammonium-N, nitrate-N, nitrite-N and organic N in these materials, and it notes that some nitrogen forms are only partly recovered.
What does FprEN 13654-1 specify?
FprEN 13654-1 specifies a chemical method for nitrogen determination in soil improvers and growing media. Clause 1 also makes clear that the Kjeldahl approach covers ammonium-N, nitrate-N, nitrite-N and organic N, while some N-N-linkages, N-O-linkages and some heterocyclic nitrogen are only partially determined.
The document is organized into the usual technical sequence: scope, normative references, terms and definitions, principle, reagents, apparatus, sampling, test sample, procedure, calculation, expression of results, test report, and validation. Annex A gives the performance characteristics of the method.
| Annex | What it covers |
|---|---|
| Annex A | Performance characteristics of the method from the interlaboratory study |
Clause 7 points users to EN 12579:2024 for sampling, so the laboratory receives a representative sample. Clause 8 then tells the user how to prepare or handle the test sample for analysis.
What are the key requirements of FprEN 13654-1?
FprEN 13654-1 is built around sulfuric acid digestion with potassium sulfate and a copper sulfate catalyst. In practice, this means the nitrogen in the sample is converted into a digest that is then measured as ammonium nitrogen by distillation, spectrophotometry or another suitable technique.
Principle and sample handling
Clause 4 states the digestion principle, and Clauses 7 and 8 set the sample handling rules. Sampling follows EN 12579:2024, and the test sample may be prepared according to prEN 13040-1:2025 or used as received, with the calculation route chosen accordingly.
For samples with high ammonium-N content in alkaline conditions, Clause 8 warns that drying can cause nitrogen losses. If the sample is suspected to contain more than 500 mg/l NH4-N on a fresh basis, it should be analysed fresh as soon as possible.
Reagents, apparatus and safety
Clauses 5 and 6 specify analytical-grade reagents, low-conductivity water, and standard Kjeldahl equipment. The apparatus list matters because the digestion needs controlled heating, suitable flasks or tubes, and a balance capable of 1.0 mg weighing.
Clause 9.1 places strong emphasis on safe handling of dusty samples and sulfuric acid digestions. The work is carried out in a fume cupboard with personal protective equipment, and the text warns about toxic fumes, bumping and local superheating.
Procedure, blank and verification
For dried samples, Clause 9.2 uses salicylic/sulfuric acid, then sodium thiosulfate or the catalyst mixture, followed by gentle digestion until no organic particles remain. Clause 9.4 gives the equivalent procedure for fresh solid and liquid samples, including size reduction or homogenization.
Clause 9.7 requires a reagent blank run in parallel with the samples. That blank is what you subtract from the sample result, so it corrects for contributions from reagents and glassware. Clause 9.8 adds a verification check with a substance of known nitrogen content, and the recovered nitrogen should exceed 95% of the calculated value.
Calculation and reporting
Clause 10 gives calculations on a dry matter basis and on a volume basis as received. Clause 11 requires subtraction of the blank and reporting either as mass/mass on dry matter basis or mass/volume as received, depending on how the sample was handled.
Clause 12 defines the test report content. In practice, this means the report must identify the sample, the method used, whether the sample was ground or unground, the nitrogen result, moisture content, laboratory bulk density, and any optional details that may have influenced the result.
What terms does FprEN 13654-1 define?
- Modified Kjeldahl method - the digestion-based method used here to determine nitrogen in soil improvers and growing media.
- Ammonium-N - the ammonium form of nitrogen measured by the method.
- Nitrate-N - the nitrate form of nitrogen that the digestion-based method addresses.
- Nitrite-N - the nitrite form of nitrogen included in the nitrogen determination.
- Organic N - nitrogen bound in organic material that is converted during digestion.
- Dry matter (DM) - the dry basis used for one of the calculation routes and for reporting results.
- Verification substance - a pure substance with known nitrogen content used to check recovery.
Who uses FprEN 13654-1?
FprEN 13654-1 is used by laboratories testing soil improvers and growing media, especially when nitrogen results are needed for product control, specification checks or conformity work. It is also relevant to producers, quality managers and buyers who need a defined test method for comparing materials such as composts, digestates, peat blends and pelletized soil improvers.
What changed in FprEN 13654-1 from the previous edition?
FprEN 13654-1 supersedes EN 13654-1:2001. The European foreword states that the normative references have been adapted and the procedure has been described in more detail.
Which standards are used with FprEN 13654-1?
- CEN/TS 17732:2022 - provides the terms and definitions used in the standard.
- EN 12579:2024 - covers sampling of soil improvers and growing media.
- prEN 13040-1:2025 - covers sample preparation, including dry matter and moisture-related preparation routes.
- prEN 13651:2025 and prEN 13652:2025 - are used in Clause 8 when checking high ammonium-N content before deciding on fresh analysis.
- ISO 5725-2 - provides the statistical basis for validation, repeatability and reproducibility.
What does the FprEN 13654-1 document contain?
The document contains the digestion procedure, reagent preparation, apparatus requirements, sample handling steps, calculation formulas and reporting rules for nitrogen determination. It also includes a safety section for sulfuric acid digestion and a validation section that points to an interlaboratory study.
Annex A summarizes performance characteristics from the validation work and lists the materials used, including composted bark, biowaste compost, green compost, solid digestate, liquid digestate, a pelleted soil improver and three growing media blends. This helps users judge whether the method has been checked on materials similar to their own.
Relations
- Effective Date
- 18-Jan-2023
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Frequently Asked Questions
FprEN 13654-1 is a draft published by the European Committee for Standardization (CEN). Its full title is "Soil improvers and growing media - Determination of nitrogen - Part 1: Modified Kjeldahl method". This standard covers: This document specifies a method for the determination of nitrogen in soil improvers and growing media. The Kjeldahl method determines ammonium-N, nitrate-N, nitrite-N and organic N content of soil improvers and growing media. Nitrogen in N-N-linkages, N-O-linkages and some heterocyclics (especially pyridine) is only partially determined [6], [7], [8]. 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, liquid digestate, soil improver (pellets, sieved 4 mm, growing media blend 1 (white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements)), growing media blend 2 (white peat, black peat, expanded perlite, lime, organic fertilizer) and growing media blend 3 (white peat, black peat, clay, inorganic fertilizer (NPK + micro elements))).
This document specifies a method for the determination of nitrogen in soil improvers and growing media. The Kjeldahl method determines ammonium-N, nitrate-N, nitrite-N and organic N content of soil improvers and growing media. Nitrogen in N-N-linkages, N-O-linkages and some heterocyclics (especially pyridine) is only partially determined [6], [7], [8]. 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, liquid digestate, soil improver (pellets, sieved 4 mm, growing media blend 1 (white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements)), growing media blend 2 (white peat, black peat, expanded perlite, lime, organic fertilizer) and growing media blend 3 (white peat, black peat, clay, inorganic fertilizer (NPK + micro elements))).
FprEN 13654-1 is classified under the following ICS (International Classification for Standards) categories: 65.080 - Fertilizers. The ICS classification helps identify the subject area and facilitates finding related standards.
FprEN 13654-1 has the following relationships with other standards: It is inter standard links to EN 13654-1:2001. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
FprEN 13654-1 is associated with the following European legislation: EU Directives/Regulations: 2019/1009; Standardization Mandates: M/564, M/564 AMD 1, M/564 AMD 2, M/XXX. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
FprEN 13654-1 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 13654-1:2025
01-december-2025
Izboljševalci tal in rastni substrati - Določanje dušika - 1. del: Spremenjena
Kjeldahlova metoda
Soil improvers and growing media - Determination of nitrogen - Part 1: Modified Kjeldahl
method
Bodenverbesserungsmittel und Kultursubstrate - Bestimmung von Stickstoff - Teil 1:
Modifiziertes Verfahren nach Kjeldahl
Amendements du sol et supports de culture - Détermination de l'azote - Partie 1:
Méthode de Kjeldahl modifiée
Ta slovenski standard je istoveten z: prEN 13654-1
ICS:
65.080 Gnojila Fertilizers
oSIST prEN 13654-1:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
oSIST prEN 13654-1:2025
oSIST prEN 13654-1:2025
DRAFT
EUROPEAN STANDARD
prEN 13654-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080 Will supersede EN 13654-1:2001
English Version
Soil improvers and growing media - Determination of
nitrogen - Part 1: Modified Kjeldahl method
Amendements du sol et supports de culture - Bodenverbesserungsmittel und Kultursubstrate -
Détermination de l'azote - Partie 1: Méthode de Bestimmung von Stickstoff - Teil 1: Modifiziertes
Kjeldahl modifiée Verfahren nach Kjeldahl
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 13654-1:2025 E
worldwide for CEN national Members.
oSIST prEN 13654-1:2025
prEN 13654-1:2025 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Reagents . 4
6 Apparatus . 4
7 Sampling . 5
8 Test sample . 5
9 Procedure . 5
9.1 Safety . 5
10 Calculation . 7
10.1 General. 7
10.2 Calculation on a dry matter basis . 7
10.3 Calculation on a volume basis . 7
11 Expression of results . 7
12 Test Report . 8
13 Validation of the method . 8
13.1 Validation in accordance with ISO 5725-2. 8
13.2 Performance characteristics. 8
Annex A (informative) Performance characteristics of the method . 9
Bibliography . 11
oSIST prEN 13654-1:2025
prEN 13654-1:2025 (E)
European foreword
This document (prEN 13654-1:2025) has been prepared by Technical Committee CEN/TC 223 “Soil
improvers and growing media”, the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 13654-1:2001.
prEN 13654-1:2025 includes the following significant technical changes with respect to
EN 13654-1:2001:
— Normative references have been adapted;
— The procedure has been described in more detail.
The Annex A is informative.
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.
oSIST prEN 13654-1:2025
prEN 13654-1:2025 (E)
1 Scope
This document specifies a method for the determination of nitrogen in soil improvers and growing media.
The Kjeldahl method determines ammonium-N, nitrate-N, nitrite-N and organic N content of soil
improvers and growing media. Nitrogen in N-N-linkages, N-O-linkages and some heterocyclics (especially
pyridine) is only partially determined [6], [7], [8].
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
3 Terms and definitions
For the purposes of this document the terms and definitions given in CEN/TS 17732:2022 apply.
4 Principle
The nitrogen content of the sample is determined using a method based on a sulfuric acid/potassium
sulfate digestion. Copper sulfate is used as the catalyst.
5 Reagents
All reagents shall be of recognized analytical grade. Use water with a specific conductivity not higher than
0,2 mS/m at 25 °C, free from the elements to be determined.
5.1 Salicylic acid/sulfuric acid, dissolve 25 g of salicylic acid (HOC H COOH) in 1 000 ml of
6 4
concentrated sulfuric acid (⍴ = 1,84 g/ml).
5.2 Potassium sulfate catalyst mixture, grind and thoroughly mix 200 g of potassium sulfate, 6 g of
copper (II) sulfate pentahydrate (This mixture may be available commercially).
5.3 Sodium thiosulfate pentahydrate, crush the crystals to form a powder that passes through a sieve
with an aperture of 0,25 mm.
5.4 Verification substances, pure substances of known nitrogen content, for example acetanilide
(C H NO), L-aspartic acid (C H NO ), or amino acids of known composition. The total content of nitrogen
8 9 4 7 4
of the calibration substance should be as similar to the sample nitrogen content as possible.
6 Apparatus
Usual laboratory apparatus, and in particular the following:
6.1 Analytical balance, capable of weighing accurately to 1,0 mg.
6.2 Kjeldahl digestion flasks or tubes, of nominal value 50 ml, suitable for the digestion system (6.3).
oSIST prEN 13654-1:2025
prEN 13654-1:2025 (E)
NOTE Larger flasks (300 ml to 500 ml) might be necessary for bulky materials or where a larger sample mass
is used.
6.3 Digestion or mineralisation system with variable heating controls.
6.4 Sieve, 5 mm square aperture size.
6.5 Stand, capable of holding the digestion flasks or tubes.
7 Sampling
Sampling is not part of the method specified in this document. EN 12579:2024 shall be followed dealing
with soil improvers and growing media. It is important that the laboratory receives a sample that is
representative of the product under consideration. The sample should not have been damaged or
changed during transport or storage.
8 Test sample
Either prepare the test sample in accordance with prEN 13040-1:2025, Clause 10 or use the sample as
received. Choose the respective calculation procedure (Clause 10).
Losses of nitrogen can occur with samples of high ammonium-N content in alkaline situations and
particularly when these samples are dried. If the sample contains (or is suspected to contain) > 500 mg/l
NH -N fresh basis, as determined by prEN 13651:2025 [1] or prEN 13652:2025 [2], analyse the fresh
material as soon as possible.
9 Procedure
9.1 Safety
SAFETY PRECAUTIONS — Care should be taken when handling samples that may contain sharps or are
of a dusty nature.
WARNING — Digestions with sulfuric acid are potentially hazardous and laboratory coats, gloves and
safety spectacles or goggles shall be used.
The digestion shall be carried out in a well-ventilated fume cupboard with the
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