FprEN 13654-2

FprEN 13654-2 is a draft European Standard from CEN for determining nitrogen in soil improvers and growing media by the Dumas method. It specifies a combustion-based laboratory method for all forms of nitrogen, including how to prepare the sample, calibrate the apparatus, calculate the result, and report it. In practice, it gives laboratories a common way to measure nitrogen in these materials on a comparable dry matter basis.

What does FprEN 13654-2 specify?

FprEN 13654-2 specifies a method for determining nitrogen in soil improvers and growing media. The document applies the dry combustion approach originally associated with Dumas and describes it as a modern automated laboratory method.

The standard 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 the performance characteristics from the interlaboratory study.

What are the key requirements of FprEN 13654-2?

Sample handling and preparation

• Clause 7 says sampling is not part of the method and refers users to EN 12579:2024. In practice, the laboratory needs a representative sample that has not been altered during transport or storage, otherwise the nitrogen result may not reflect the product.
• Clause 8 requires test sample preparation in accordance with prEN 13040-1:2025, Clause 10. Liquid samples may be used without drying, which matters for materials such as liquid digestate.
• For samples that may contain more than 500 mg/l NH4-N, the document points to the preparation route in prEN 13040-1:2025, Clause 10.2 c. This is important because ammonium-N can be lost during drying in alkaline samples.

Measurement principle and apparatus

• Clause 4 measures nitrogen by heating the sample to at least 900 °C in oxygen gas. Mineral and organic nitrogen compounds are oxidized and/or volatilized, and the instrument determines the released nitrogen according to the manufacturer’s system.
• Clause 6 requires an analytical balance readable to 1.0 mg and a Dumas apparatus with a detector for the nitrogen gas formed. For users, this means the result depends on both the weighing step and the instrument setup, so the manufacturer’s manual is part of the working method.

Reagents and calibration

• Clause 5 requires reagents of recognized analytical grade and calibration substances with known nitrogen content, such as acetanilide, L-aspartic acid, amino acids of known composition, or other certified substances. The chosen calibration material should have a nitrogen content similar to the sample being tested.
• Clause 9.2 requires calibration according to the manufacturer’s manual. This makes the instrument-specific operating instructions part of the analysis, rather than a fixed universal setting.

Determination, correction and reporting

• Clause 9.3 says the amount of test sample depends on expected nitrogen content and instrument capacity, and the sample is analyzed in dried, ground form unless the manufacturer’s procedure says otherwise.
• Clause 9.4 determines residual moisture in the analyzed sample using prEN 13040-1:2025, Clause 11. That moisture value is then used in Clause 10 to correct the primary result to a dry matter basis.
• Clauses 11 and 12 require results to be expressed on a mass/mass dry matter basis and the test report to identify the standard, the sample, the analytical methods, whether the sample was ground or unground, the result, moisture content, and any factors that could have affected the result. This is the part buyers and auditors usually check first.

Validation and performance

• Clause 13 states that the method was validated in accordance with ISO 5725-2 and that repeatability and reproducibility data are given in Annex A. For users, this shows the document includes performance data from an interlaboratory study, which helps judge method fit for routine control.

What terms does FprEN 13654-2 define?

• Dumas method - A dry combustion method in which nitrogen is released from the sample by high-temperature oxidation in oxygen.
• Soil improvers and growing media - The product family covered by the standard, including materials used to improve soil or support plant growth.
• NH4-N - Ammonium-nitrogen, a form of nitrogen that can be lost during drying under alkaline conditions.
• DM - Dry matter, used to express the corrected nitrogen result on a dry basis.
• Repeatability - The closeness of agreement between results obtained under the same conditions in the interlaboratory validation context.
• Reproducibility - The closeness of agreement between results obtained under changed laboratory conditions in the validation study.

Who uses FprEN 13654-2?

FprEN 13654-2 is used by laboratories that measure nitrogen in soil improvers and growing media. It is also relevant to manufacturers, quality managers, and technical buyers who need comparable nitrogen data for product control, batch release, and specification checking.

The standard is especially useful where products may contain different nitrogen forms, because the method is intended for all forms of nitrogen. It also supports work linked to product conformity and reporting on a dry matter basis.

What changed in FprEN 13654-2 from the previous edition?

FprEN 13654-2 supersedes EN 13654-2:2001. The foreword states one significant technical change: the scope and applicability have been adapted with respect to the EU Fertilizer Product Regulation.

Which standards are used with FprEN 13654-2?

• 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 - Covers sample preparation and the determination of dry matter content, moisture content, and laboratory bulk density.
• ISO 5725-2 - Provides the statistical approach used for validating repeatability and reproducibility.
• prEN 13651:2025 and prEN 13652:2025 - Are named for checking ammonium-N when deciding how to prepare samples that may lose nitrogen during drying.

What does the FprEN 13654-2 document contain?

The document contains the test principle, reagent and apparatus requirements, sampling and test-sample preparation rules, the analytical procedure, and the calculation and reporting approach. It also gives the test report content that should be recorded for traceability.

For performance evaluation, Annex A presents the interlaboratory study material set and the resulting repeatability and reproducibility data. The annex tables support method validation and help users judge how the procedure performed across different soil improvers and growing media.