oSIST prEN 13038:2025
(Main)Soil improvers and growing media - Determination of electrical conductivity
- Abstract
This document specifies an instrumental method for the routine determination of electrical conductivity in a water extract of a soil improver or growing medium. The determination is carried out to obtain an indication of the content of water-soluble electrolytes in either soil improvers or growing media.
NOTE This method has been validated in an interlaboratory study with specific products that were present on the market during the study (as included in Annex A, being bark (Pinus pinaster, 20 mm to 40 mm fraction), coir pith (0 mm to 12 mm, washed and buffered), biowaste compost (Rottegrad 3), green compost (Rottegrad 5, 0 mm to 15 mm), liquid digestate, expanded clay, whole granules, 8 mm to 16 mm, growing media blend 1 (white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements)), growing media blend 2 (white peat, black peat, expanded perlite, lime, organic fertilizer) and growing media blend 3 (white peat, black peat, clay, inorganic fertilizer (NPK + micro elements))).
- Status
- Not Published
- Public Enquiry End Date
- 01-Dec-2025
- Technical Committee
- KAT - Soil quality
- Current Stage
- 4020 - Public enquire (PE) (Adopted Project)
- Start Date
- 08-Oct-2025
- Due Date
- 25-Feb-2026
- Completion Date
- 15-Dec-2025
- Mandate
- M/XXX - M/XXX
oSIST prEN 13038:2025 is the Slovenian publication of draft European Standard prEN 13038 from CEN for soil improvers and growing media. It specifies an instrumental routine method for determining electrical conductivity in a water extract, so the result gives an indication of the content of water-soluble electrolytes in the material. The document is aimed at laboratories and product-control users who need a consistent way to compare batches or monitor quality.
What does oSIST prEN 13038:2025 specify?
oSIST prEN 13038:2025 specifies a routine test method for measuring electrical conductivity in soil improvers and growing media. The method uses a water extract and reports the conductivity after correction to 25 °C.
The document is organized into clauses on scope, normative references, terms and definitions, principle, reagents, apparatus, sampling, preparation, procedure, test report, and validation. Annex A is informative and gives performance characteristics from an interlaboratory study.
| Annex | What it covers |
|---|---|
| Annex A | Performance characteristics of the method, based on interlaboratory data |
Sampling is not part of the method itself. For sampling, the document points to EN 12579:2024, and for sample preparation it points to prEN 13040-1:2025.
What are the key requirements of oSIST prEN 13038:2025?
Sample handling and preparation
oSIST prEN 13038:2025 requires a representative sample that has not been changed during transport or storage. The sample is then prepared according to prEN 13040-1:2025, and laboratory bulk density is determined as part of the reported information.
This matters because conductivity depends on how the sample is taken and prepared. If the sample is not representative, the result can misstate the soluble salt level of the product.
Extraction conditions
oSIST prEN 13038:2025 extracts the sample with water at 22 °C ± 3 °C using an extraction ratio of 1 to 5. The method gives separate extraction approaches for solid materials, pre-shaped materials, and liquid or pasty materials.
In practice, the operator must use the correct sample volume, water volume, and container size for the material form. That keeps the extract comparable across different product types.
Mixing, filtration, and measurement
oSIST prEN 13038:2025 calls for shaking or mixing for 1 h at 150 rpm ± 25 rpm while keeping the sample suspended without damaging its structure. The extract is then filtered, with the first 10 ml discarded, and alternative clarification steps may be used if paper filtration is too slow.
The filtrate is measured with a conductivity meter that has temperature correction set to 25 °C. The document also notes that contamination of electrodes and air bubbles can affect the reading, so cleaning and careful handling matter.
Meter calibration
oSIST prEN 13038:2025 uses potassium chloride solutions of 0.100 mol/l and 0.0100 mol/l to check the conductivity meter. The cell constant is calculated from the measured response and must stay within 5 % of the manufacturer’s value.
This gives the user a way to confirm that the meter is behaving correctly before measuring samples. It is the control step that supports reliable routine testing.
Reporting and method validation
oSIST prEN 13038:2025 requires the test report to identify the standard, identify the sample, give results as whole numbers in mS/m, note any non-standard or optional operations, and include laboratory bulk density. The method was validated in line with ISO 5725-2, and Annex A summarizes repeatability and reproducibility from an interlaboratory study on nine materials.
That tells the reader how to document the result and how the method performed across different sample types. It is useful when comparing results between laboratories.
What terms does oSIST prEN 13038:2025 define?
- Electrical conductivity - the ability of an aqueous extract to conduct electricity as a function of ion concentration.
- Specific electrical conductivity - the conductivity value measured on the extract and reported with temperature correction to 25 °C.
- Water extract - the liquid obtained when the sample is extracted with water under the method conditions.
- Cell constant - the calibration factor calculated from the potassium chloride solution and used to set the conductivity meter.
- Repeatability - the closeness of agreement between results obtained under the same conditions in the same laboratory.
- Reproducibility - the closeness of agreement between results obtained under different laboratories and conditions.
- Laboratory bulk density - the bulk density of the prepared sample as determined for the laboratory test portion.
Who uses oSIST prEN 13038:2025?
oSIST prEN 13038:2025 is used by testing laboratories that measure salt-related properties in soil improvers and growing media. It is also relevant to manufacturers, quality managers, and buyers who need a routine check on product consistency.
Inspection bodies and certification or conformity-assessment teams can use it when they need a standardized conductivity result for market control or product comparison. The method is especially useful when electrical conductivity is used as an indicator of dissolved electrolytes in different material types.
What changed in oSIST prEN 13038:2025 from the previous edition?
oSIST prEN 13038:2025 will supersede EN 13038:2011. The document states that the significant technical change is an adaptation of scope and applicability with respect to the EU-Fertilizer Product Regulation.
Which standards are used with oSIST prEN 13038:2025?
- CEN/TS 17732:2022 - provides the terminology used for soil improvers and growing media.
- EN 12579:2024 - covers sampling of soil improvers and growing media.
- prEN 13040-1:2025 - covers sample preparation and the determination of laboratory bulk density.
- ISO 5725-2 - provides the statistical basis used for validation, repeatability, and reproducibility.
What does the oSIST prEN 13038:2025 document contain?
The document contains a principle section, reagent and apparatus lists, and step-by-step procedures for different material forms. It also gives filtration and conductivity-meter calibration instructions, including a formula for calculating the cell constant.
It includes the required contents of the test report and a validation section that explains how the method was checked. Annex A summarizes the interlaboratory study and the performance characteristics derived from it, including the tested materials and precision data.
Relations
- Revises
SIST EN 13038:2012 - Soil improvers and growing media - Determination of electrical conductivity - Effective Date
- 01-Nov-2025
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Frequently Asked Questions
oSIST prEN 13038:2025 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Soil improvers and growing media - Determination of electrical conductivity". This standard covers: This document specifies an instrumental method for the routine determination of electrical conductivity in a water extract of a soil improver or growing medium. The determination is carried out to obtain an indication of the content of water-soluble electrolytes in either soil improvers or growing media. NOTE This method has been validated in an interlaboratory study with specific products that were present on the market during the study (as included in Annex A, being bark (Pinus pinaster, 20 mm to 40 mm fraction), coir pith (0 mm to 12 mm, washed and buffered), biowaste compost (Rottegrad 3), green compost (Rottegrad 5, 0 mm to 15 mm), liquid digestate, expanded clay, whole granules, 8 mm to 16 mm, growing media blend 1 (white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements)), growing media blend 2 (white peat, black peat, expanded perlite, lime, organic fertilizer) and growing media blend 3 (white peat, black peat, clay, inorganic fertilizer (NPK + micro elements))).
This document specifies an instrumental method for the routine determination of electrical conductivity in a water extract of a soil improver or growing medium. The determination is carried out to obtain an indication of the content of water-soluble electrolytes in either soil improvers or growing media. NOTE This method has been validated in an interlaboratory study with specific products that were present on the market during the study (as included in Annex A, being bark (Pinus pinaster, 20 mm to 40 mm fraction), coir pith (0 mm to 12 mm, washed and buffered), biowaste compost (Rottegrad 3), green compost (Rottegrad 5, 0 mm to 15 mm), liquid digestate, expanded clay, whole granules, 8 mm to 16 mm, growing media blend 1 (white peat, green compost, wood fibre, lime, inorganic fertilizer (NPK + micro elements)), growing media blend 2 (white peat, black peat, expanded perlite, lime, organic fertilizer) and growing media blend 3 (white peat, black peat, clay, inorganic fertilizer (NPK + micro elements))).
oSIST prEN 13038:2025 is classified under the following ICS (International Classification for Standards) categories: 65.080 - Fertilizers. The ICS classification helps identify the subject area and facilitates finding related standards.
oSIST prEN 13038:2025 has the following relationships with other standards: It is inter standard links to SIST EN 13038:2012. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
oSIST prEN 13038:2025 is associated with the following European legislation: EU Directives/Regulations: 2019/1009; Standardization Mandates: M/564, M/564 AMD 1, M/564 AMD 2, M/XXX. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
oSIST prEN 13038:2025 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2025
Izboljševalci tal in rastni substrati - Določanje električne prevodnosti
Soil improvers and growing media - Determination of electrical conductivity
Bodenverbesserungsmittel und Kultursubstrate - Bestimmung der elektrischen
Leitfähigkeit
Amendements du sol et supports de culture - Détermination de la conductivité électrique
Ta slovenski standard je istoveten z: prEN 13038
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
prEN 13038
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080 Will supersede EN 13038:2011
English Version
Soil improvers and growing media - Determination of
electrical conductivity
Amendements du sol et supports de culture - Bodenverbesserungsmittel und Kultursubstrate -
Détermination de la conductivité électrique Bestimmung der elektrischen Leitfähigkeit
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 223.
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.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
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 13038:2025 E
worldwide for CEN national Members.
prEN 13038:2025 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Reagents . 4
6 Apparatus . 5
7 Sampling . 5
8 Preparation . 5
9 Procedure . 5
9.1 Extraction of materials in solid form . 5
9.2 Extraction of material in pre-shaped form . 6
9.3 Extraction of liquid or pasty materials . 6
9.4 Filtration . 6
9.5 Measuring conductivity of the potassium chloride solutions . 6
9.6 Measurement of the specific electrical conductivity of the filtrates . 6
10 Test report . 7
11 Validation of the method . 7
11.1 Validation in accordance with ISO 5725-2. 7
11.2 Performance characteristics. 7
Annex A (informative) Performance characteristics of the method . 8
Bibliography . 10
prEN 13038:2025 (E)
European foreword
This document (prEN 13038:2025) has been prepared by Technical Committee CEN/TC 223 “Soil
improvers and growing media”, the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 13038:2011.
prEN 13038:2025 includes the following significant technical changes with respect to EN 13038:2011:
— adaption of scope and applicability with respect to the EU-Fertilizer Product Regulation [3].
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
prEN 13038:2025 (E)
1 Scope
This document specifies an instrumental method for the routine determination of electrical conductivity
in a water extract of a soil improver or growing medium. The determination is carried out to obtain an
indication of the content of water soluble electrolytes in either soil improvers or growing media.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
CEN/TS 17732:2022, Soil improvers and growing media – Terminology
EN 12579:2024, Soil improvers and growing media - Sampling
prEN 13040-1:2025, Soil improvers and growing media — Sample preparation — Part 1: Sample
preparation for chemical and physical tests, determination of dry matter content, moisture content and
laboratory bulk density
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 17732:2022 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
electrical conductivity
ability of an aqueous extract of the sample to conduct electricity as a function of the ion concentration
4 Principle
A sample is extracted with water at 22 °C ± 3,0 °C in an extraction ratio of 1 to 5 (1 V sample + 5 V water)
to dissolve the electrolytes. The specific electrical conductivity of the extract is measured and the result
is adjusted to a measurement temperature of 25 °C.
5 Reagents
5.1 Water, having an electrical conductivity not higher than 0,2 mS/m at 25 °C.
5.2 Potassium chloride solution, c(KCl) = 0,100 mol/l.
Dissolve 7,456 g potassium chloride (KCl), previously dried for 2 h at 105 °C, in water (5.1) and dilute to
1 000 ml. The specific electrical conductivity of this solution at 25 °C is 1 290 mS/m.
5.3 Potassium chloride solution, c(KCl) = 0,0100 mol/l.
Add 100,0 ml of potassium chloride solution (5.2) into a 1 000 ml volumetric flask and dilute to the
1 000 ml mark with water (5.1) at 20 °C. The specific electrical conductivity of this solution at 25 °C is
141 mS/m.
...