FprEN 15957

• Abstract:

  This document specifies a method for the extraction of phosphorus soluble in neutral ammonium citrate in inorganic fertilizers.

• Status: Not Published
• Publication Date: 13-Jan-2027
• ICS: 65.080 - Fertilizers
• Technical Committee: CEN/TC 260 - Fertilizers and liming materials
• Drafting Committee: CEN/TC 260/WG 7 - Chemical analysis
• Current Stage: 5020 - Submission to Vote - Formal Approval
• Start Date: 24-Sep-2026
• Due Date: 12-Mar-2027
• Completion Date: 24-Sep-2026
• Directive: 2019/1009 - 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
• Ref Project: kSIST FprEN 15957:2026 - Inorganic fertilizers - Extraction of phosphorus which is soluble in neutral ammonium citrate

• Revises: EN 15957:2011 - Fertilizers - Extraction of phosphorus which is soluble in neutral ammonium citrate
• Effective Date: 02-Apr-2025

FprEN 15957 is a draft European Standard from the European Committee for Standardization (CEN) for inorganic fertilizers. It specifies a laboratory method for extracting phosphorus soluble in neutral ammonium citrate, so laboratories can produce the same extract for comparing fertilizer results. The method is aimed at analytical work on fertilizer samples.

What does FprEN 15957 specify?

FprEN 15957 specifies the extraction of phosphorus soluble in neutral ammonium citrate from inorganic fertilizers. The scope is the extraction step itself, not the broader sampling process or the later reporting of phosphorus results.

FprEN 15957 is organized into clauses on scope, normative references, terms and definitions, principle, sampling and sample preparation, reagents, apparatus, procedure, and test report, followed by a bibliography. Clause 5 points readers to recommended sampling and sample-preparation documents, so the method can be applied to a representative laboratory sample.

What are the key requirements of FprEN 15957?

FprEN 15957 requires extraction at 65 °C using a neutral ammonium citrate solution at pH 7 under defined conditions. In practice, this means the analyst must control both temperature and solution composition, because those two factors govern how much phosphorus is brought into solution.

Clause 5 says sampling is not part of the method, but the laboratory sample must be representative and not altered during transport or storage. Sample preparation is carried out in accordance with EN 1482-2, and grinding of the laboratory sample is recommended for homogeneity. That matters because uneven material can give uneven extraction results.

Clause 6 limits the water and reagent quality. The water used shall be distilled or demineralized with conductivity below 0.5 mS/m at 25 °C, and the neutral ammonium citrate solution is prepared to pH 7 with a specified composition and stored in a closed container with periodic pH checks. This keeps the extraction medium consistent from one test to the next.

Clause 7 lists the apparatus needed for the method, including a pH-meter, Erlenmeyer flask, graduated flasks, a thermostatically controlled water bath with shaking, and a dry pleated phosphate-free filter. In practice, the equipment has to support stable heating, agitation, and clean filtration.

Clause 8 gives the extraction sequence. A 1 g or 3 g test portion is mixed with 100 ml of preheated ammonium citrate solution, then extracted for exactly 1 h at 65 °C while suspended by stirring or periodic shaking. After cooling, the contents are transferred quantitatively, made up to volume, and filtered, discarding the first about 50 ml of filtrate. This produces a clear extract suitable for the next analytical step.

Clause 9 defines the minimum test report content. The report must identify the sample, name the method as FprEN 15957, record the sampling date and procedure if known, note when extraction finished, and list any optional details or incidents that could have influenced the result. That supports traceability when results are reviewed or compared.

What terms does FprEN 15957 define?

FprEN 15957 uses the terms and definitions from EN 12944-1 and EN 12944-2. In this method, a few practical terms are especially important.

• Laboratory sample - the sample received by the lab for analysis, which should represent the product being tested.
• Test portion - the 1 g or 3 g amount taken from the laboratory sample for the extraction.
• Neutral ammonium citrate solution - the reagent at pH 7 used to extract the phosphorus.
• pH (potential of hydrogen) - the measure used to set and check the neutrality of the reagent.
• Phosphate-free filter - a filter that avoids adding phosphorus to the extract.

Who uses FprEN 15957?

FprEN 15957 is used by laboratories that test inorganic fertilizers and by technical staff who prepare samples and run chemical extractions. It is also relevant to fertilizer producers, quality control teams, and contract laboratories that need the same extraction conditions for routine analysis. The method supports repeatable results across the fertilizer sector.

What changed in FprEN 15957 from the previous edition?

FprEN 15957 supersedes EN 15957:2011. The foreword states two significant technical changes: distilled water characteristics were added, and the reference to Regulation (EC) No 2003/2003 was removed.

Which standards are used with FprEN 15957?

FprEN 15957 refers to EN 1482-2 for general sample preparation provisions. It uses EN 12944-1 and EN 12944-2 for the terms and definitions needed to read the method consistently. The bibliography also points to EN 1482-1 as the recommended general sampling method.

What does the FprEN 15957 document contain?

FprEN 15957 contains a defined preparation of the neutral ammonium citrate reagent, including pH control and storage instructions. It also includes the apparatus list, the extraction procedure with time, temperature, mixing and filtration steps, and the minimum test-report items.

The document is written as a practical laboratory method, so the key content is the sequence of actions needed to obtain the extract. For users, the most useful parts are the reagent preparation details, the extraction conditions, and the reporting checklist.

SLOVENSKI STANDARD
oSIST prEN 15957:2026
01-februar-2026
Anorganska gnojila - Ekstrakcija fosforja, topnega v amonijevem citratu v
nevtralnem mediju
Inorganic fertilizers - Extraction of phosphorus which is soluble in neutral ammonium
citrate
Anorganische Düngemittel - Extraktion des in neutralem Ammoniumcitrat löslichen
Phosphors
Engrais inorganiques - Extraction du phosphore soluble dans du citrate d’ammonium
neutre
Ta slovenski standard je istoveten z: prEN 15957
ICS:
65.080 Gnojila Fertilizers
oSIST prEN 15957:2026 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 15957:2026
oSIST prEN 15957:2026
DRAFT
EUROPEAN STANDARD
prEN 15957
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2025
ICS 65.080 Will supersede EN 15957:2011
English Version
Inorganic fertilizers - Extraction of phosphorus which is
soluble in neutral ammonium citrate
Engrais inorganiques - Extraction du phosphore Anorganische Düngemittel - Extraktion des in
soluble dans du citrate d'ammonium neutre neutralem Ammoniumcitrat löslichen Phosphors
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 260.
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.

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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 15957:2025 E
worldwide for CEN national Members.

oSIST prEN 15957:2026
prEN 15957:2025 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Sampling and sample preparation . 4
6 Reagents . 4
7 Apparatus . 5
8 Procedure . 5
8.1 Test portion . 5
8.2 Extraction . 5
9 Test report . 6
Bibliography . 7

oSIST prEN 15957:2026
prEN 15957:2025 (E)
European foreword
This document (prEN 15957:2025) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
This document is currently submitted to CEN Enquiry.
This document will supersede EN 15957:2011.
This document includes the following significant technical changes with respect to EN 15957:2011:
a) characteristics of distilled water added;
b) reference to Regulation (EC) No 2003/2003 removed.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States sub
...