🌱 Extraction of water-soluble calcium, magnesium, sodium and sulfur (in the form of sulfates) from fertilizers — one extract for determining each nutrient, PN-EN 15961

Physicochemistry PN-EN 15961

Overview

WHAT THE STANDARD COVERS. The scope from the PKN catalogue card, quoted in full: "This European Standard specifies a method for the extraction of water-soluble calcium, magnesium, sodium and sulfur (in the form of sulfates), so that the same extract can be used for the determination of each nutrient required. The method is solely applicable to fertilizers listed in Regulation (EC) 2003/2003, Annex I [2], for which a declaration of the water-soluble calcium, magnesium, sodium and sulfur (in the form of sulfates) is provided for in this Regulation." (our translation of the Polish card). So the standard does not measure anything itself — it provides a solution in which the laboratory determines the nutrient according to another standard. The card does not give the extraction conditions (sample mass, volume and temperature of the water, time).

STATUS (state of the card on 29 September 2026). The card of PN-EN 15961:2017-02 (Polish version) has no withdrawal note — the standard is CURRENT. Published 18-05-2018, 10 pages, PKN technical committee KT 156 (Fertilizers), ICS 65.080; "Introduces: EN 15961:2017 [IDT]"; "Supersedes: PN-EN 15961:2011 - English version, PN-EN 15961:2011 - Polish version". The PKN search for "PN-EN 15961" (29 September 2026) shows the 2017-02 edition in Polish and in English and both 2011 editions labelled "Wycofana" (withdrawn). The Estonian EVS (read on 29 September 2026) gives "Valid from 03.02.2017" for EVS-EN 15961:2017 and, in the history — besides the 2011 and 2017 editions — the draft "prEN 15961": a revision is under way.

REGULATION. Regulation (EU) 2019/1009, Article 51: "Regulation (EC) No 2003/2003 is repealed with effect from 16 July 2022. References to the repealed Regulation shall be construed as references to this Regulation." The condition in the scope of the standard ("fertilizers listed in Regulation (EC) 2003/2003, Annex I") therefore refers to an act no longer in force; how to read it today for fertilising products under Regulation 2019/1009 — WE DO NOT DECIDE.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17 September 2026, read on 28 September 2026). All records of number 15961: 37 entries at 14 laboratories. Forms: "PN-EN 15961:2017-02" — 13 laboratories, "PN-EN 15961:2017" — AB 759. The "Laboratories" tab searches for records BEGINNING with "PN-EN 15961" and will show all 14 — checked with the tab query on the labcoda.pl production server on 29 September 2026: 14. Current scopes on the PCA website (read on 29 September 2026, issues from 7 March 2025 to 5 August 2026): all entries stand in the valid issues, every pair of range numbers from the copy appears in the current document and no entry is suspended; the full records of the reference documents agree with the copy. At AB 333 the first document for magnesium is garbled in the copy (two numbers overlaid); in the PCA scope it reads PN-EN 15960:2011, PN-EN 15961:2017-02 and PN-EN 16197:2013-05.

WHAT IT STANDS WITH IN THE SCOPES. Never alone — always with a determination standard: calcium by titration (at AB 827 "manganometric") — with PN-EN 16196:2013-05; magnesium by flame atomic absorption spectrometry (FAAS) — with PN-EN 16197:2013-05, at AB 006 also by titration with PN-EN 16198:2013-05 and by ICP-OES with procedure IPL-006; sodium (AB 006) — ICP-OES with procedure IPL-007; sulfur in the form of sulfates by the gravimetric method — with PN-EN 15749 (usually with the note "metoda A", method A; AB 284 cites the 2012 edition, the others 2023-01), at AB 006 and AB 180 also with PN-EN 15926:2011. Seven laboratories (AB 213, AB 277, AB 312, AB 333, AB 820, AB 827, AB 921) also record PN-EN 15960:2011 in the same entry — the entry is then usually called "Calcium content", "magnesium" or "sulfur", without the words "water-soluble". AB 213 combines both extractions with PN-EN ISO 11885:2009 (ICP-OES) for many elements at once. PN-EN 15960 (total extraction), PN-EN 16196 and PN-EN 16197 have separate entries in this knowledge base.

MATRICES. "Mineral (inorganic) fertilizers" — 12 laboratories; AB 006 adds organo-mineral and organic fertilizers, compost, growing media and plant growth aids, and AB 213 has only plant growth aids (soil improvers, growing media). The card restricts the method to fertilizers in Annex I of Regulation 2003/2003; whether it covers organic fertilizers, compost and growing media — WE DO NOT DECIDE.

RANGES. Calcium as CaO: lower limits from 0.5 % (AB 284, AB 312, AB 820, AB 827) to 2.00 % (AB 317, AB 787), upper limits from 35.0 % (AB 317) to 60.0 % (AB 312, AB 820, AB 827, AB 921); AB 333 records (1.5 – 70.0) % without stating the form, and AB 213 in its multi-element ICP-OES determination — (0.010 – 20) % CaO. Magnesium, usually as MgO: lower limits from 0.01 % (AB 312) to 1.0 % (AB 284, AB 779), upper limits from 5.00 % (AB 317) to 41.5 % (AB 006, AB 180). Sulfur as SO3: lower limits from 0.25 % (AB 180, AB 312) to 5.0 % (AB 820), upper limits up to 62.5 % (AB 180, AB 333) — and at AB 006 "(1,3 - 250) % SO3": this is what converting the upper limit of 99.9 % S to SO3 gives; a mass fraction above 100 % has no physical meaning (the record stands like this in the PCA scope, issue no. 25 of 20 February 2026).

ALONGSIDE THIS STANDARD. Our copy has no calcium, magnesium, sodium or sulfur described as "water-soluble" without PN-EN 15961 — every such entry for fertilizers cites it. For other water-soluble nutrients the same laboratories cite other extraction and determination standards, among others PN-EN 15477:2009, PN-EN 15958:2011 with PN-EN 15959 and PN-EN 16962:2018-03.

WHAT WE DO NOT GIVE. We did not have the text of the standard — PKN sells it (10 pages). We do not give the sample mass, the volume and temperature of the water, the time and manner of shaking, the filtration or the preparation of the solution for the determinations.

Method principle

According to the card of the standard, water-soluble calcium, magnesium, sodium and sulfur in the form of sulfates are extracted from the fertilizer with water so that one extract serves for the determination of each of these nutrients; the determination is carried out according to a separate standard (in the scopes: PN-EN 16196 — calcium, PN-EN 16197 or PN-EN 16198 — magnesium, PN-EN 15749 — sulfates). We DO NOT GIVE the extraction conditions — we did not have the text of the standard.

Applications

• Declared contents of water-soluble calcium, magnesium, sodium and sulfur (sulfates) in mineral fertilizers — in the scopes of 14 laboratories
• Preparing one extract for several determinations: calcium (PN-EN 16196), magnesium (PN-EN 16197, PN-EN 16198, ICP-OES), sodium (ICP-OES), sulfates (PN-EN 15749)

Key parameters

Standard

Standard number

PN-EN 15961:2017-02 (wersja polska; wprowadza EN 15961:2017 [IDT])

Title (PL)

Nawozy — Ekstrakcja rozpuszczalnego w wodzie wapnia, magnezu, sodu i siarki obecnej w postaci siarczanów

Title (EN)

Fertilizers — Extraction of water-soluble calcium, magnesium, sodium and sulfur in the form of sulfates

Step-by-step procedure

1. Status of the document

   PKN card: PN-EN 15961:2017-02 is current (state of the card on 29 September 2026); the scope refers to Regulation (EC) No 2003/2003, which has not been in force since 16 July 2022.

2. Extraction

   Water-soluble calcium, magnesium, sodium and sulfur in the form of sulfates are extracted from the fertilizer sample with water (card); conditions NOT GIVEN.

3. Determinations in the extract

   Each nutrient is determined from the same extract according to a separate standard — in the scopes PN-EN 16196, PN-EN 16197, PN-EN 16198, PN-EN 15749 or ICP-OES with a procedure.

Reagents, media and consumables

Health and safety (OHS)

• NOTE ON SUBSTANCE: the result depends on the determination standard cited alongside — when asking about a test, check which technique the laboratory uses for the given nutrient
• NOTE ON SUBSTANCE: the scope of the standard refers to the repealed Regulation 2003/2003; for fertilizers outside its Annex I (organic, compost, growing media) ask the laboratory on what basis the method is applied

Frequently asked questions