🌱 Phosphorus soluble in neutral ammonium citrate and in water in mineral fertilizers — chapter 6 of the standard, in accreditation scopes always together with the gravimetric determination of phosphorus in the extract according to PN-EN 15959; PN-C-87015 (withdrawn standard)

Physicochemistry PN-C-87015

Overview

WHAT THE STANDARD COVERS. The "Scope" field of the PKN card for PN-C-87015:1988 (Polish version), in full: "Five methods are given for determining the content of total phosphates, available phosphates and water-soluble phosphates in fertilizers containing 5-50 percent (m/m) of phosphates expressed as phosphorus oxide. The methods of extracting phosphates from fertilizers are presented (table). The performance of the determination is described, and the apparatus, reagents and calculation of results are given". Title from the card: "Nawozy sztuczne -- Metody badań zawartości fosforanów" (Artificial fertilizers -- Test methods for phosphate content). The previous edition, PN-C-87015:1980 "Nawozy sztuczne -- Metody badań różnych form fosforu" (Artificial fertilizers -- Test methods for various forms of phosphorus), had in the "Scope" field: "The subject of the standard is the test methods for total, available and water-soluble phosphorus in artificial fertilizers containing 5÷50% phosphorus expressed as P2O5." We have not read the text of the standard — we do not know what chapter 6 contains, which extraction (solution, temperature, time, test portion) and which final determination it concerns, or how the result is calculated in it.

STATUS (PKN cards as of 09.11.2026). The card for PN-C-87015:1988 (Polish version) has the label "Withdrawn" and the line "Withdrawal date: 07-09-2015"; there is no "Replaced by" field — the card indicates no successor (by comparison, the card for the 1980 edition has the label "Withdrawn and replaced by" and that field). The 1988 edition: published 04-03-1988, 9 pages, price group E, Chemistry Sector, KT 156 for Fertilizers, ICS 65.080, "Replaces: PN-C-87015:1980 - Polish version"; the card has no "Implements" field — it is a national standard, not an adoption of an EN or ISO standard. The card for PN-C-87015:1980 (Polish version): published 14-11-1980, 10 pages, KT 156 for Fertilizers, withdrawal date 01-01-1989, "Replaced by: PN-C-87015:1988 - Polish version". A search for "PN-C-87015" in the PKN catalogue (09.11.2026) returns only these two cards. The card does not answer the question of what replaced the standard; the withdrawal does not change the content of the method — a laboratory that applies it works according to a withdrawn document for which there is no newer edition. What stands next to this standard in the scopes — next paragraph.

NEXT TO THIS STANDARD — PN-EN 15959 AND PN-EN 15957. In each of the 7 scope items, PN-EN 15959 stands next to PN-C-87015 — the standard for determining phosphorus in a ready fertilizer extract by the gravimetric method (a separate entry of this database: "Phosphorus in fertilizer extracts — gravimetric method (quinoline phosphomolybdate) — PN-EN 15959"); the "Scope" field of the PKN card for PN-EN 15959:2024-05: "This document specifies a method for the determination of phosphorus in fertilizer extracts". PN-EN 15959 does not extract, so it does not take over the whole of PN-C-87015 — in the scope items both standards stand together, not interchangeably. Five laboratories (AB 180, AB 779, AB 787, AB 827, AB 921) have two separate items in their scope: "phosphorus soluble in neutral ammonium citrate" — with PN-EN 15957:2011 (extraction of phosphorus soluble in neutral ammonium citrate, a separate entry of this database) and PN-EN 15959 — and "phosphorus soluble in neutral ammonium citrate and in water" — with PN-C-87015:1988 chapter 6 and PN-EN 15959. The methodologies under the two forms of citation are therefore different: this is not an alternative but a division of tasks — for the form "in ammonium citrate and in water" the laboratories cite PN-C-87015, and for the determination of phosphorus PN-EN 15959. Whether chapter 6 describes only the extraction or also the determination, we cannot confirm without the text of the standard. EN 15957:2011 (clause 1, the part made available by the publisher) concerns fertilizers for which solubility in neutral ammonium citrate is laid down in Annex I of Regulation (EC) No 2003/2003; extraction: 1 g or 3 g of fertilizer in 100 ml of neutral ammonium citrate solution (pH 7), exactly 1 h at 65 °C (clauses 4, 6.2, 8). That text says nothing about the form "in ammonium citrate and in water". Status (PKN cards, 09.11.2026): PN-EN 15959:2024-05 (Polish version: published 11-12-2025, 16 pages, implements EN 15959:2023 [IDT], no withdrawal label) replaced PN-EN 15959:2011 (Polish version: published 04-11-2013, withdrawn 27-05-2024); PN-EN 15957:2011 (Polish version: published 11-06-2015, 10 pages, implements EN 15957:2011 [IDT]) — no withdrawal label.

FORMS OF PHOSPHORUS IN THE REGULATIONS. Regulation (EU) 2019/1009 (original text, OJ L 170 of 25.6.2019), Annex III "Labelling requirements", for inorganic macronutrient fertilisers (PFC 1(C)(I)) and for organo-mineral fertilisers (PFC 1(B)) lists for declaration: total phosphorus pentoxide, water-soluble phosphorus pentoxide, phosphorus pentoxide soluble in neutral ammonium citrate and — where soft ground phosphate is present — soluble in formic acid. The form "soluble in ammonium citrate and in water" combined does not appear in this text (the whole wording searched for the word "cytrynian" (citrate) — three places, all in Annex III). The term "mineral fertiliser" may be used, among other conditions, when the declared phosphorus is solely in the form of phosphate and the fertiliser meets at least one solubility criterion: in water at least 40 %, in neutral ammonium citrate at least 75 % or (soft rock phosphate only) in formic acid at least 55 % of total phosphorus. We have not read the amendments to the regulation after 2019. Whether phosphorus "in ammonium citrate and in water" from the scopes is the same quantity as phosphorus "soluble in neutral ammonium citrate" in the regulation and in PN-EN 15957, we cannot decide without the text of PN-C-87015. The Regulation of the Minister of Agriculture and Rural Development of 9 August 2024 on the implementation of certain provisions of the Act on fertilizers and fertilization (Journal of Laws 2024 item 1261, in force) gives no test methods and no standard designations (there is no PN designation anywhere in the text): it entrusts physical, physicochemical and chemical testing of fertilizers to the Institute of Soil Science and Plant Cultivation, the Institute of New Chemical Syntheses and accredited bodies (§ 4 point 1), and requires solid mineral fertilizers with declared phosphorus to contain at least 2 % (m/m) of phosphorus expressed as P2O5 (§ 14 point 5) — without indicating the form of phosphorus.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, read 09.11.2026; current scope documents on the PCA website, 09.11.2026; "Laboratories" tab on labcoda.pl, 09.11.2026). The number 87015 appears in the copy in 7 items at 7 Polish laboratories — one each: AB 180, AB 312, AB 333, AB 779, AB 787, AB 827, AB 921; laboratories of other countries do not have it. Counted over the reference document, normative basis and search text fields, by the number 87015 alone — every notation of the designation is included. Notations: "PN-C-87015:1988 rozdz. 6" (AB 180, AB 921), "PN-C-87015:1988 rozdz.6" (AB 312), "PN-C-87015:1988 pkt.6" (AB 333, AB 779), "PN-C-87015:1988 rozd.6" (AB 827) and in the copy "P N-C-87015:1988 rozdz. 6" with a space (AB 787) — the current PCA scope document of that laboratory reads "PN-C-87015:1988 rozdz. 6", so the space arose when the document was transferred to the copy. Always chapter or point 6, never the whole standard. Each item from the copy appears in the current PCA scope document with the same wording (tested characteristic, range, technique, standards): AB 180 — issue 24 of 19.06.2026, AB 312 — 25 of 15.06.2026, AB 333 — 24 of 24.06.2025, AB 779 — 21 of 05.08.2026, AB 787 — 14 of 21.11.2025, AB 827 — 22 of 22.07.2026, AB 921 — 18 of 03.04.2026; for AB 312 the copy has PN-EN 15959:2024-05 written twice, the PCA document once. The "Laboratories" tab ("PN-C-87015", matching by the beginning of the notation) shows 6 laboratories and 6 items — without AB 787, whose notation in the copy begins with "P N-C" (query of the tab on labcoda.pl, 09.11.2026).

WHAT THE LABORATORIES TEST (copy of the database, complete items — 7). Test object: "Nawozy mineralne (nieorganiczne)" (mineral (inorganic) fertilizers) (6) or "Nawozy nieorganiczne (nawozy mineralne)" (inorganic fertilizers (mineral fertilizers)) (AB 180); technique in all 7 — "gravimetric method". Tested characteristic: content of phosphorus soluble in neutral ammonium citrate and in water — AB 180, AB 827, AB 921, AB 312 ("in neutral ammonium citrate solution and in water"), AB 779 ("dissolved"), AB 787 ("in ammonium citrate neutral and water (P2O5)"); AB 333 — one item "content of phosphorus soluble after extraction": in mineral acids, in neutral ammonium citrate, in water and in water and in neutral ammonium citrate, with P content calculated; in it PN-C-87015:1988 point 6 stands together with PN-EN 15956:2011, PN-EN 15957:2011, PN-EN 15958:2011 and PN-EN 15959:2024-05, without assigning a standard to a form (PN-EN 15956:2011 — extraction of phosphorus soluble in mineral acids, PN-EN 15958:2011 — in water; both in the Polish version of 11-06-2015, no withdrawal label, PKN cards 09.11.2026; each has a separate entry of this database). Ranges: AB 180 (0.22–24.0) % P and (0.50–55.0) % P2O5, AB 312 (1.0–55.0) % P2O5, AB 333 (2.0–52.0) % P2O5, AB 779 (1.0–55.0) % P2O5, AB 787 (1.00–50.0) % (P2O5 in the name of the characteristic), AB 827 (0.5–50.0) % P2O5, AB 921 (2.5–55) % P2O5. Next to PN-C-87015: PN-EN 15959:2024-05 in 6 items and the withdrawn edition PN-EN 15959:2011 in 1 (AB 787). Neighbourhood in the copy: a separate item "phosphorus soluble in neutral ammonium citrate" (without "and in water") with PN-EN 15957:2011 and PN-EN 15959 is held by 13 Polish laboratories — 13 items (AB 006, AB 180, AB 277, AB 284, AB 317, AB 759, AB 779, AB 787, AB 798, AB 820, AB 827, AB 921, AB 930); counted over the methodology and parameter fields containing the word "cytrynian" (citrate), excluding items on citric acid in food and the combined item of AB 333.

WHERE AN APPARENTLY CORRECT RESULT IS EASY TO GET. Extraction: "phosphorus soluble in …" is phosphorus extracted under the conditions of the given standard; "in ammonium citrate and in water" (PN-C-87015 chapter 6) and "in neutral ammonium citrate" (PN-EN 15957) are two different items in the scopes of five laboratories — the result of one must not appear in the report under the name of the other, and comparison with the declaration on the label requires the form that was declared (in Regulation (EU) 2019/1009 separately: water-soluble and soluble in neutral ammonium citrate). Measurement: phosphorus in the extract is determined according to PN-EN 15959 — its conditions are described in a separate entry; AB 787 cites the 2011 edition, withdrawn on 27-05-2024 and replaced by the 2024-05 edition. Calculation: the result is given as P2O5 or as P — AB 180 declares both ranges, AB 333 calculates P; 0.22 % P corresponds to 0.50 % P2O5 and 24.0 % P to 55.0 % P2O5, i.e. the number in P2O5 is about 2.29 times larger (ratio of the molar masses of P2O5 and 2 P) — a result without a named form is unreadable. Field of application: the "Scope" field of the card concerns fertilizers containing 5–50 % phosphates expressed as phosphorus oxide, while the ranges of the items extend from 0.5 % to 55 % P2O5; we have not read the text of the standard, so we do not know whether the interval 5–50 % is a limit of application of the method.

WHAT WE DO NOT GIVE. We have not read the text of PN-C-87015:1988 (in the PKN catalogue only for sale; we did not find it in open access) — we do not give the content of chapter 6: the solution, temperature, time and test portion of the extraction, the method of determination, formulae, precision or the table of extraction methods; we do not know whether chapter 6 covers extraction with water and then ammonium citrate, or a single extraction. We have not established why PKN withdrew the standard without a successor. We did not check the status of EN 15959:2023 and EN 15957:2011 in the publisher's catalogue in this reading (the catalogue page did not display data). We have not read the amendments to Regulation (EU) 2019/1009 after 2019 or Regulation (EC) No 2003/2003.

Method principle

According to the PKN card, the standard gives methods for determining total phosphates, available phosphates and water-soluble phosphates in fertilizers containing 5–50 % phosphates (as phosphorus oxide), with a table of extraction methods. In accreditation scopes its chapter 6 serves the form "phosphorus soluble in neutral ammonium citrate and in water", and phosphorus in the extract is determined gravimetrically according to PN-EN 15959; result — in % P2O5 or in % P. We do not give the procedure of chapter 6 — we have not read the text of the standard.

Applications

• Mineral (inorganic) fertilizers — content of phosphorus soluble in neutral ammonium citrate and in water (items of accreditation scopes)
• According to the PKN card, the standard also covers total, available and water-soluble phosphates — the scopes cite only chapter 6
• Always together with PN-EN 15959 (gravimetric determination of phosphorus in the extract) — a separate entry of this database; the form "in neutral ammonium citrate" without water has a separate item in the scopes with PN-EN 15957
• In accreditation scopes: 7 Polish laboratories, ranges from 0.5 % to 55 % P2O5, gravimetric method

Key parameters

Standard

Standard number

PN-C-87015:1988 (Polish version; withdrawn 07-09-2015 with no successor indicated)

Title (PL)

Nawozy sztuczne — Metody badań zawartości fosforanów

Title (EN)

Artificial fertilizers — Test methods for phosphate content

Step-by-step procedure

1. Choice of the form of phosphorus

   Establish whether phosphorus soluble in neutral ammonium citrate and in water (PN-C-87015 chapter 6) or in neutral ammonium citrate alone (PN-EN 15957) is determined — in the scopes these are separate items.

2. Extraction

   According to chapter 6 of PN-C-87015 — solution, conditions and test portion NOT GIVEN (we have not read the text of the standard).

3. Determination of phosphorus in the extract

   By the gravimetric method according to PN-EN 15959 (current edition: 2024-05) — a separate entry of this database.

4. Result

   Phosphorus content in % P2O5 or in % P, with the name of the form and of the expression of the result. PN-C-87015:1988 — withdrawn 07-09-2015 with no successor indicated (PKN card as of 09.11.2026).

Required equipment and apparatus

Health and safety (OHS)

• Fertilizer dust during grinding and weighing — respiratory protection
• Reagents for the gravimetric determination of phosphorus — according to the safety data sheets and the entry on PN-EN 15959
• TECHNICAL NOTE: withdrawn standard without a successor; the form "in ammonium citrate and in water" is a different item in the scopes from "in neutral ammonium citrate"

Frequently asked questions