SIST EN 13038:2012

SIST EN 13038:2012 is the Slovenian adoption of EN 13038:2011, a European Standard for measuring electrical conductivity in a water extract of soil improvers and growing media. It specifies an instrumental routine method that gives an indication of the content of water-soluble electrolytes in those products.

What does SIST EN 13038:2012 specify?

SIST EN 13038:2012 specifies how to determine electrical conductivity in soil improvers and growing media by measuring the conductivity of a water extract. The method is intended for routine use, so it is written for repeatable laboratory control rather than product design.

The standard does not apply to liming materials or to preformed materials such as mineral wool slabs and foam slabs. It also notes that legal declaration requirements may differ from the standard itself.

The document is organized into:

• Scope
• Normative references
• Terms and definitions
• Principle
• Reagents
• Apparatus
• Preparation
• Procedure
• Precision
• Test report
• Informative Annex A

What are the key requirements of SIST EN 13038:2012?

SIST EN 13038:2012 requires a water extraction at controlled temperature, a calibrated conductivity meter, and a blank check before results are reported. In practice, the method is built to show the amount of dissolved salts in a sample in a consistent way.

Sample preparation and extraction

Clause 7 requires preparation according to EN 13040:2007 and determination of compacted laboratory bulk density from EN 13040:2007. That means the sample must be made ready in a defined way before any conductivity test, so the result can be linked to a known sample state.

Clause 4 states that the test portion is extracted with water at (22 ± 3,0) °C using a 1:5 extraction ratio. The extract is then adjusted to 25 °C for the conductivity result, which matters because conductivity changes with temperature.

Procedure for different sample sizes

Clause 8 gives two extraction routes, one for test samples passing through a 20 mm sieve and one for samples passing through a 40 mm sieve. The sample mass is taken as an amount equivalent to a defined sample volume, so the method ties the test to volume as well as weight.

After shaking for 1 h, the extract is filtered and the first 10 ml are discarded. If paper filtration is too slow or impossible, an alternative such as centrifugation or glass fibre filter papers may be used, but the technique used must be reported.

Calibration, blank and measurement control

Clause 8.5 requires calibration with potassium chloride solutions and checking the cell constant against the manufacturer’s value. This keeps the conductivity meter traceable enough for routine work and helps detect electrode contamination or drift.

Clause 8.6 requires measurement of the filtrate within one hour of extraction, with temperature correction set to 25 °C. The blank must be below twice the detection limit of the conductivity meter before results are reported, so the lab has to control water, glassware and filter cleanliness.

Precision and reporting

Clause 9 points to precision data from an interlaboratory trial in Annex A and says the repeatability and reproducibility apply to separately prepared samples. That helps users judge how much variation to expect between tests and between laboratories.

Clause 10 requires the test report to identify the standard used, identify the sample, give the result as millisiemens per metre, record any non-standard or optional operations, and state the compacted laboratory bulk density. In practice, the report must show both the result and anything that could have influenced it.

What terms does SIST EN 13038:2012 define?

SIST EN 13038:2012 uses these key terms in its method:

• Electrical conductivity - the ability of an aqueous extract to conduct electricity as a function of ion concentration.
• Specific electrical conductivity - the conductivity value reported for the filtrate, corrected to 25 °C.
• Water extract - the liquid obtained by extracting the sample with water under the specified conditions.
• Conductance (G) - the measured electrical conductance used to calculate the cell constant.
• Cell constant (k) - the instrument parameter calculated from potassium chloride solution measurements.
• Blank - a control run without sample to show the contribution from water, glassware and filter paper.
• Soil improver - the product type covered by the scope and tested as a sample.
• Growing medium - the other product type covered by the scope and tested as a sample.

Who uses SIST EN 13038:2012?

SIST EN 13038:2012 is used by laboratories that test soil improvers and growing media for routine quality control. It is also relevant to producers, quality managers, and buyers who need a consistent conductivity result for product specification, release, or comparison.

The method is especially useful in horticulture and related product testing, where dissolved electrolytes can affect product performance. Regulatory or declaration work may also use it when electrical conductivity is part of product information.

What changed in SIST EN 13038:2012 from the previous edition?

SIST EN 13038:2012 supersedes EN 13038:1999. The foreword states that the main change from the previous edition is a change of scope.

Which standards are used with SIST EN 13038:2012?

SIST EN 13038:2012 relies on these normative references:

• EN 13040:2007 - provides sample preparation for chemical and physical tests and the compacted laboratory bulk density method.
• EN ISO 3696 - specifies the water quality used for reagent water in the method.
• ISO 1770 - provides the thermometer type used for temperature measurement.

What does the SIST EN 13038:2012 document contain?

SIST EN 13038:2012 contains a defined extraction and measurement procedure, a calibration step using potassium chloride solutions, and a blank check before reporting. Clause 8 includes separate handling for samples passing through 20 mm and 40 mm sieves, plus filtration options when standard paper filtration is not suitable.

The document also includes a formula for the cell constant and an informative precision annex. Annex A summarizes an interlaboratory trial for three sample types and reports repeatability and reproducibility data for specific electrical conductivity. The test report clause lists the information that must accompany the result, including the standard reference, sample identification, the conductivity result, any deviations from the method, and compacted laboratory bulk density.