oSIST prEN 13654-2:2025

oSIST prEN 13654-2:2025 is the Slovenian version of the CEN draft European Standard prEN 13654-2, published by SIST. It specifies the Dumas combustion method for determining nitrogen in soil improvers and growing media, including sample preparation, analysis, calculation and reporting. It is written for laboratories, producers and quality teams that need a standardized way to measure nitrogen across different material types.

What does oSIST prEN 13654-2:2025 specify?

oSIST prEN 13654-2:2025 specifies a method for determining nitrogen in soil improvers and growing media by dry combustion, also called the Dumas method. Clause 1 states that the method applies to all forms of nitrogen and that modern automated equipment improves the original manual approach.

The document is organized into clauses on scope, normative references, terms and definitions, principle, reagents, apparatus, sampling, test sample, procedure, calculation, expression of results, test report and validation. Annex A gives performance characteristics from an interlaboratory study.

What are the key requirements of oSIST prEN 13654-2:2025?

oSIST prEN 13654-2:2025 centers on a combustion test that converts nitrogen in the sample to a measurable gas signal. In practice, the main tasks are to prepare the sample correctly, calibrate the instrument, run the Dumas apparatus, correct the result for moisture and report it on a dry matter basis.

Sample handling and preparation

• Clause 7 says sampling is handled by EN 12579:2024, not by this method. The laboratory must receive a representative sample that has not been altered during transport or storage.
• Clause 8 requires test sample preparation according to prEN 13040-1:2025. Liquid samples can be used without drying, which matters for materials such as liquid digestate.
• Clause 8 also warns that drying can cause nitrogen losses in samples with high ammonium-N in alkaline conditions. If the sample contains or is suspected to contain more than 500 mg/l ammonium-N, a different preparation route from prEN 13040-1:2025 is used.

Instrument setup and analysis

• Clause 4 requires heating the sample to at least 900 °C in oxygen gas. This oxidizes or volatilizes mineral and organic nitrogen compounds so the instrument can measure total nitrogen.
• Clause 5 requires reagents of recognized analytical grade and calibration substances with known nitrogen content. The calibration material should be close to the expected sample nitrogen level, which improves measurement reliability.
• Clause 6 requires an analytical balance readable to 1.0 mg and a Dumas apparatus with a detector for nitrogen gas. The manufacturer’s manual controls setup and operation.
• Clause 9 requires calibration of the apparatus with one of the substances listed in Clause 5 and analysis according to the manufacturer’s manual. Safety precautions are noted for dusty samples and samples that may contain sharps.

Results, moisture correction and reporting

• Clause 9.4 and Clause 10 require residual moisture to be measured and used to correct the nitrogen result to dry matter basis. This matters because the reported value must represent the material after moisture correction, not just the analyzed portion.
• Clause 11 requires results to be expressed on a mass/mass dry matter basis, either as whole figures or as a percentage with one decimal place.
• Clause 12 requires the test report to identify the standard, the sample, the analytical methods used, whether the sample was ground or unground, the nitrogen result, the moisture content and any relevant deviations or optional details.

Method validation

• Clause 13 states that the method was validated in accordance with ISO 5725-2. Annex A gives the repeatability and reproducibility data derived from the interlaboratory study and shows the method was checked on nine material types.

What terms does oSIST prEN 13654-2:2025 define?

oSIST prEN 13654-2:2025 uses the terms and definitions from CEN/TS 17732:2022. The following expressions are especially important when reading or applying the method:

• Dumas method - a dry combustion technique that measures nitrogen after the sample is burned in oxygen.
• Soil improvers - materials used to improve soil properties and treated as a main application area for the method.
• Growing media - materials used as substrates for plant growth, including blended and amended products.
• Dry matter basis - the reporting basis used after correcting for moisture.
• Residual moisture - the moisture remaining in the analyzed sample and used for the calculation correction.
• Calibration substance - a substance with known nitrogen content used to set or verify the instrument response.
• Repeatability - the closeness of results under the same conditions in one laboratory.
• Reproducibility - the closeness of results between different laboratories.

Who uses oSIST prEN 13654-2:2025?

oSIST prEN 13654-2:2025 is used by analytical laboratories that test composts, digestates, peat-based blends, pellets and other soil improvers or growing media. It is also relevant to manufacturers, importers, quality managers and conformity assessment teams that need nitrogen data for product control or technical documentation. Because the document ties its validation to products used in an interlaboratory study, it is particularly useful where routine testing has to match real market materials.

What changed in oSIST prEN 13654-2:2025 from the previous edition?

oSIST prEN 13654-2:2025 supersedes EN 13654-2:2001. The European foreword states one significant technical change: the scope and applicability were adapted with respect to the EU Fertilizer Product Regulation.

Which standards are used with oSIST prEN 13654-2:2025?

• CEN/TS 17732:2022 - provides the terms and definitions used in the document.
• EN 12579:2024 - gives the sampling procedure for soil improvers and growing media.
• prEN 13040-1:2025 - gives sample preparation steps and the moisture-content procedure used here.
• ISO 5725-2 - provides the statistical basis used for validation and the repeatability and reproducibility assessment.
• prEN 13651:2025 and prEN 13652:2025 - are used in the note for checking ammonium-N when the sample may need special preparation.

What does the oSIST prEN 13654-2:2025 document contain?

The document contains the full Dumas test sequence, from principle and reagents through apparatus, sampling, sample preparation, calibration, measurement and calculation. It also includes the reporting rules and a validation section that explains how the method was checked. Annex A provides performance data for nine material types, which helps laboratories understand how the method behaved in the interlaboratory study.