🌱 Available phosphorus, potassium, magnesium and manganese in organic soil according to PN-R-04024

Environment PN-R-04024

Overview

STATUS (state of the PKN card on 22.09.2026). PN-R-04024:1997 — publication 25-04-1997, 6 pages, ICS 13.080.10. The card has no withdrawal note and no "Replaced by" row — the standard is CURRENT. It is a purely Polish standard: the card does not give an "Implements" field, i.e. it does not implement any EN or ISO document.

WHAT THE STANDARD DOES: ONE EXTRACT, FOUR ELEMENTS, THREE TECHNIQUES. From the PKN card: methods are given for determining, IN THE SAME EXTRACT from organic soil obtained with a hydrochloric acid solution, four elements available to plants — phosphorus, potassium, magnesium and manganese. For phosphorus a COLORIMETRIC method is indicated, for potassium FLAME PHOTOMETRY, and for magnesium and manganese ATOMIC ABSORPTION SPECTROMETRY. This is something that cannot be seen from the name of the test in the report: the four results come from one portion of the extract, but from three different instruments. What is common is the way of extraction — and it is this that decides the meaning of the word "available".

"AVAILABLE" MEANS: EXTRACTED BY THIS SOLUTION. The result is neither the total content of the element in the soil nor the amount that the plant will actually take up. It is the amount passing into the extract made according to this standard. A different extraction method will give a different number for the same soil — and both will be correct, each within its own method. That is why the result "available phosphorus" from this standard is not compared with a result obtained by another methodology without checking how the extract was made.

ORGANIC SOILS ONLY — AND THIS IS ALSO HOW IT IS IN THE SCOPES. The title and scope of the standard speak of organic soils (peat and muck soils), and this is also how laboratories describe the test object: "Gleba organiczna" [organic soil] — 36 entries, "Gleby organiczne" [organic soils] — 23 entries, altogether 59 of the 61 entries measured. Other standards of this series serve mineral soils, and this methodology does not cover them.

DIVISION INTO CLAUSES — WHAT EACH CLAUSE MEANS (A MEASUREMENT, NOT A GUESS). In the accreditation scopes, 10 entries at 5 laboratories cite the standard with a clause number or with clauses excluded. Matching these citations with the methodology standing in the same row gives an unambiguous assignment: • clause 4 — PHOSPHORUS (three entries "pkt 4" with the phosphorus methodology; a fourth entry "z wyłączeniem pkt 5, 6 i 7" [excluding clauses 5, 6 and 7] is also with phosphorus); • clause 5 — POTASSIUM ("pkt 5" with potassium, "z wyłączeniem pkt 4, 6 i 7" [excluding clauses 4, 6 and 7] also with potassium); • clause 6 — MAGNESIUM ("pkt 6" with magnesium, "z wyłączeniem pkt 4, 5 i 7" [excluding clauses 4, 5 and 7] also with magnesium); • clause 7 — MANGANESE ("pkt 7" with manganese); • clauses 1–3 — the common part: one citation reads "p. 1, 2, 3, 7" and stands with manganese, i.e. the laboratory indicated the introductory part together with the clause for its element. The two forms of citation — indicating a clause and excluding the other three — give the same division, each from the other side. This is a cross-confirmation, not a reading of the text of the standard: WE DO NOT HAVE THE STANDARD ITSELF, so we do not know what exactly stands in clauses 1–3, and we do not guess it.

THE FOURTH ELEMENT IS HARDLY EVER ACCREDITED. Of the 61 entries, only 2 concern manganese. Phosphorus, potassium and magnesium each appear in a dozen or more entries (phosphorus: 12 + 7 entries in two wordings of the methodology, magnesium: 9 + 8, potassium: 8 + 7). The standard gives four elements from one extract, but in practice laboratories accredit three — manganese is left aside.

FOURTEEN WORDINGS OF THE NAME OF THE SAME TEST. The methodology next to this standard is written in the scopes in fourteen different ways, with the most frequent pair differing only in word order: "Zawartość przyswajalnego fosforu" (12 entries) and "Zawartość fosforu przyswajalnego" (7) [both: content of available phosphorus], likewise for magnesium (9 and 8) and potassium (8 and 7). Some scopes add the oxide form — "(P2O5)", "(K2O)". Searching for the test by name in the scopes therefore requires covering both word orders, and for phosphorus and potassium also the oxide notation.

THE TRAP OF THE NUMBER: THE SAME "04024" IN A DIFFERENT SERIES. The accreditation scopes also contain two entries with the number 04024 that are NOT from this standard: "PN-82/Z-04024/02" and "PN-Z-04024-3:2012 pkt 6 + Ap1:2013" — this is the Z series, i.e. air purity protection, and both entries concern the determination of BARIUM in workplace air, not soil. A search for the string "04024" alone will find them together with the soil ones, although they have nothing in common. THE SERIES LETTER IS PART OF THE DESIGNATION OF THE STANDARD — a number without the letter does not identify the standard.

SCALE. 61 entries at 24 laboratories across all forms of notation. Matching by the BEGINNING of the notation gives 59 entries at 22 laboratories — the difference is small here, because the standard rarely stands in a joint citation; the exception is three entries where PN-EN ISO 11885:2009 (determination of elements by ICP-OES) stands next to it, i.e. the laboratory combines the extract from this standard with a different final measurement technique.

Method principle

A test portion of organic soil is extracted with a hydrochloric acid solution, giving one extract common to all four determinations. In the same extract, the following are determined: phosphorus by a colorimetric method (colour reaction and absorbance measurement), potassium by flame photometry (emission in the flame), and magnesium and manganese by atomic absorption spectrometry. The result expresses the content of the AVAILABLE form, i.e. the form that passes into the extract made according to this standard — not the total content of the element in the soil.

Applications

• Chemical and agricultural analysis of organic soils — peat and muck soils
• Establishing the need for phosphorus, potassium and magnesium fertilisation on land on organic soils
• Soil testing as part of the assessment of meadow and pasture sites
• Soil documentation when the use of land is changed
• Reading an accreditation scope in which one standard is divided into clauses — one per element

Key parameters

Standard

Standard number

PN-R-04024:1997 (wersja polska)

Title (PL)

Analiza chemiczno-rolnicza gleby — Oznaczanie zawartości przyswajalnego fosforu, potasu, magnezu i manganu w glebach organicznych

Title (EN)

(brak wersji obcojęzycznej — norma wyłącznie polska)

Step-by-step procedure

1. Checking that the soil is organic

   The standard concerns organic soils only. Applying it to a mineral soil goes beyond the scope of the standard — other standards of this series serve mineral soils.

2. Preparing the sample

   Drying, grinding and sieving the soil and weighing the portion for extraction. The details are in clauses 1–3 of the standard, whose content WE DO NOT HAVE.

3. Preparing the hydrochloric acid extract

   A step common to all four determinations: one extract is made from one portion, and phosphorus, potassium, magnesium and manganese are measured from it.

4. Determination of phosphorus — clause 4 of the standard

   Colorimetric method: colour reaction and measurement of absorbance against a calibration curve. Some scopes give the result converted to P2O5 — the conversion factor must be stated in the report, because the number changes more than twofold.

5. Determination of potassium — clause 5 of the standard

   Flame photometry. Here too some scopes give the result as K2O.

6. Determination of magnesium — clause 6 of the standard

   Atomic absorption spectrometry from the same extract.

7. Determination of manganese — clause 7 of the standard

   Atomic absorption spectrometry. In the accreditation scopes a rare determination: 2 entries out of 61 — before placing an order it is worth checking whether the laboratory has precisely this clause.

8. Recording the citation and the form of the result

   In the report, give the standard in the form consistent with the accreditation scope, and with the division into clauses — the clause number. State whether the result is in the form of the element or of the oxide, and that it concerns the AVAILABLE form, i.e. the form extracted by this method.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The "available" result depends on the way of extraction — comparing it with a result from another methodology without checking the extract leads to false conclusions about the nutrient status of the soil
• The standard concerns ORGANIC soils only; applying it to a mineral soil goes beyond its scope
• A citation without a clause number does not say which of the four elements the laboratory has accredited — the methodology column decides
• Manganese is sometimes available only at individual laboratories — the absence of this determination from the scope is easy to overlook, because the standard "is there"
• A result converted to the oxide (P2O5, K2O) is a different number from the result for the element — the form must be stated in the report
• The string "04024" also occurs in the Z series (air purity, determination of barium) — a number without the series letter does not identify the standard

Frequently asked questions