🌿 Available manganese in mineral soil — persulphate, formaldoxime or AAS method, PN-R-04019

Environment PN-R-04019

Overview

WHAT THE STANDARD COVERS. The scope from the PKN catalogue card, quoted in full: "Three kinds of test methods are established: spectrophotometric with ammonium persulphate (oxidation of manganese ions and measurement of the intensity of the violet colour), spectrophotometric formaldoxime method (reaction of formaldoxime with manganese ions and measurement of the colour intensity of the complex) and the atomic absorption spectrometry method. An assessment of the manganese content is given in the form of a table." The card does not say what the soil extract is prepared with.

STATUS (state of the card on 28 September 2026). The card carries the heading "Withdrawn" and the row "Date of withdrawal: 01-09-2014". There are no "Superseded by" and "Supersedes" fields. Edition: published 31-03-1993, 4 pages, PKN technical committee KT 90 (Soil Cultivation and Horticulture), ICS 13.080.10. The PKN search for "przyswajalnego" (available) (29 September 2026) shows only standards of the same series — PN-R-04016 … PN-R-04025 of 1992–1997 and two amendments to them (Az1:2002, Az1:2004) — a successor WE HAVE NOT ESTABLISHED. A regulation citing this standard as a test method WE HAVE NOT ESTABLISHED. Manganese in organic soils has a separate standard of this series, PN-R-04024:1997 (described separately in this knowledge base).

EXTRACT AND TECHNIQUE — ACCORDING TO A PUBLICATION OF THE NATIONAL AGRICULTURAL CHEMISTRY STATION. W. Lipiński, "Zasobność gleb Polski w mikroelementy" (Micronutrient status of Polish soils), Studia i Raporty IUNG-PIB 34(8), 2013: in the agricultural chemistry stations manganese in mineral soils is determined after extraction with 1 mol/dm³ hydrochloric acid, by AAS; in 1965–1983 it was extracted according to Schachtschabel with 1 N magnesium sulphate and determined colorimetrically. The author notes that for manganese "the determination of additional parameters, including pH, is necessary" (our translation) — without pH the result cannot be assessed.

CONTENT ASSESSMENT — THE TABLE FROM THE STANDARD. KSChR publication, Table 2 ("Source: PKN, 1993"), mg of manganese per kg of soil, for four pH ranges in 1 mol/dm³ KCl (up to 4.5; 4.6–5.0; 5.1–5.5; above 5.5) and four agronomic categories (I — very light soils, II — light, III — medium, IV — heavy). The low-content limits rise from below 9 (pH up to 4.5, category I) to below 110 mg/kg (pH above 5.5, category IV), and the high-content limits from above 90 to above 1100 mg/kg; at pH above 5.5 a high content is above 170, 400, 830 and 1100 mg/kg for categories I–IV. In 2009–2012, according to this assessment, 3 % of the soils tested by the stations had a low content, 93 % a medium and 4 % a high content (Table 9 of the publication). In 2013 the author writes (p. 122): "The currently applicable limit values used to evaluate soils for their micronutrient content are presented in Tables 1–7 (…)" (our translation); whether the stations apply them today — WE HAVE NOT ESTABLISHED.

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 R-04019: 16 entries at 16 laboratories — the same ones that cite the standards on available zinc, copper and iron. Forms: "PN-R-04019:1993" — 10 laboratories; "PN-93/R-04019" — 6 (AB 317, AB 333, AB 759, AB 789, AB 798, AB 921). The "Laboratories" tab searches for records BEGINNING with "PN-R-04019" and will show 10 laboratories; it will not show the six with the form "PN-93/R-04019". Technique at all of them: flame atomic absorption spectrometry (FAAS); none records the persulphate or formaldoxime method. Current scopes on the PCA website (read on 29 September 2026): all 16 entries stand in the valid issues with the same range as in the copy, and none is suspended.

CLAUSES OF THE STANDARD IN THE SCOPES — A TRACE OF THE THREE METHODS. Four laboratories cite clauses 1, 2 and 5 (AB 312, AB 317, AB 921, AB 1172), and two exclude clauses 3 and 4 (AB 759, AB 787). In line with the order on the card this looks like a division: clause 3 — the persulphate method, clause 4 — formaldoxime, clause 5 — AAS; we did not have the text of the standard, so this is a conclusion from the records, not a quotation. AB 333 excludes "clause 3.5" — just as in the standards on zinc, copper and iron; what this clause contains — WE HAVE NOT ESTABLISHED.

RANGES AND CLASS LIMITS — A PLACE FOR A RESULT THAT CANNOT BE CLASSIFIED. The highest high-content limit — 1100 mg/kg (category IV, pH above 5.5) — is not covered by the range of any of the 16 laboratories: the highest reach is AB 759 (up to 1050 mg/kg), then AB 312, AB 317, AB 827 and AB 1186 (up to 1000). AB 789 (up to 800) ends below the 830 limit, and AB 921 (up to 600) also below 750. Nine laboratories end at 500 mg/kg or lower, below the limits of 510, 750, 830 and 1100: AB 284, AB 333, AB 779, AB 787 (up to 500), AB 798 and AB 823 (up to 400), AB 277 (up to 320), AB 1172 (up to 300) and AB 930 (up to 270); the last three also do not cover the limits of 390 and 400, AB 1172 and AB 930 not the 310 limit, and AB 930 not 280. At the bottom, AB 1172 starts at 20 mg/kg — above seven low-content limits (9, 12, 13, 15, 16, 17 and 18 mg/kg for soils of lower pH and lighter categories); seven laboratories start at 10 — above the 9 mg/kg limit. The class depends on pH and category, so whether a given result can be assessed has to be checked for the specific soil.

WHAT WE DO NOT GIVE. We did not have the text of the standard — PKN sells it (4 pages). We do not give the sample mass, the extraction conditions, the reagent concentrations and wavelengths of the two spectrophotometric methods or the AAS conditions, the calibration curve, the formula or the precision.

Method principle

According to the card of the standard, manganese is determined by one of three methods: spectrophotometrically after oxidation of manganese ions with ammonium persulphate to the violet-coloured form, spectrophotometrically after reaction with formaldoxime, whose coloured complex is measured, or by atomic absorption spectrometry. According to the KSChR publication (2013), the mineral-soil extract is prepared with 1 mol/dm³ hydrochloric acid and manganese is determined by AAS. The result in mg/kg is assessed with the table from the standard — for the pH range in KCl and the agronomic category of the soil. We DO NOT GIVE the extraction and measuring conditions — we did not have the text of the standard.

Applications

• Assessment of the available-manganese status of mineral soils for fertiliser advice — in accreditation scopes exclusively agricultural soil-testing stations (16 laboratories), all by AAS
• The assessment requires the soil pH in KCl and the agronomic category — without them the result in mg/kg gives no class
• Not for organic soils: for them there is PN-R-04024:1997 (0.5 mol/dm³ HCl extract; according to the KSChR publication limits of 100 and 400 mg/kg)

Key parameters

Standard

Standard number

PN-R-04019:1993 (wersja polska)

Title (PL)

Analiza chemiczno-rolnicza gleby — Oznaczanie zawartości przyswajalnego manganu

Title (EN)

Agricultural chemical analysis of soil — Determination of available manganese content

Step-by-step procedure

1. Status of the document

   PKN card: standard withdrawn on 01-09-2014, no successor indicated (state of the card on 28 September 2026). In the report the full designation with the year and the method are given: PN-R-04019:1993, AAS, persulphate or formaldoxime.

2. Extract

   Mineral soil is extracted with 1 mol/dm³ hydrochloric acid (according to the KSChR publication). Sample mass and conditions NOT GIVEN.

3. Measurement

   Manganese in the extract is determined by one of the three methods of the standard; in accreditation scopes all laboratories record flame AAS.

4. Soil pH and category

   The assessment needs the soil pH in 1 mol/dm³ KCl and its agronomic category (I–IV).

5. Result and assessment

   The manganese content in mg/kg is assessed with the table for the given pH and category. For heavy soil with pH above 5.5 the high-content limit (1100 mg/kg) lies outside the accreditation range of every one of the 16 laboratories.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hydrochloric acid is corrosive — work with gloves and goggles, in a fume cupboard; its safety data sheet applies
• Ammonium persulphate is a strong oxidant and may sensitise the respiratory tract — its safety data sheet applies
• TECHNICAL NOTE: without pH in KCl and the agronomic category the manganese result gives no class — the same result may be a high or a low content

Frequently asked questions