🌿 Dry matter and water content of soil — gravimetric method (105 °C)

Environment PN-ISO 11465

Overview

The water and dry matter content is a basic quantity accompanying every analysis of soil — the results of chemical determinations are referred to the dry matter, and the field moisture characterises the state of the soil at the moment of sampling. ISO 11465:1993 specifies a method for the determination of the dry matter and water content of samples of soil on a mass basis; it is applied to all kinds of soils, with separate procedures for air-dry samples (e.g. prepared in accordance with ISO 11464) and for field-moist ones. The water content on a volume basis is determined in accordance with ISO 11461. The dry matter is defined as the dry residue of the soil in % by mass after drying in accordance with the standard, and the water content as the mass of water evaporated on drying to constant mass at 105 °C divided by the dry matter of the soil and multiplied by 100; constant mass is that at which the difference between two successive weighings of the cooled sample at an interval of 4 h does not exceed 0.1 % (m/m) of the last mass — 16–24 h of drying is usually sufficient. The Polish version is PN-ISO 11465:1999.

A WITHDRAWN STANDARD — REPLACED BY A BROADER ONE (status of the PKN cards as of 23.09.2026). The description above corresponds to ISO 11465:1993, introduced as PN-ISO 11465:1999. PKN withdrew this standard on 4 March 2026 and replaced it with PN-EN ISO 11465:2026-03 (English version; introduces EN ISO 11465:2025 and ISO 11465:2025 [IDT]) under a different title: "Sludge and solid environmental matrices — Determination of the dry residue or the water content and calculation of the dry matter fraction on a mass basis" (our translation of the Polish title on the PKN card). The new edition also replaced PN-EN 12880:2004 and PN-EN 15934:2013-02. According to the card it covers sludge, sludge products, treated biowaste, soil and waste — samples with more than 1 % of dry residue or of water: method A (determination of the dry residue) for sludge, sludge products, biowaste, soil and solid waste, method B (determination of the water content) for liquid waste and for samples with volatile substances other than water. How the procedure according to the 2026 edition differs from the one described here — WE HAVE NOT ESTABLISHED: we do not have the text of the standard.

SCALE OF CITATIONS (measured on 23.09.2026 on the copy of the accreditation scope database of 11.09.2026). The "Laboratories" tab searches by the notation "PN-ISO 11465" — 47 laboratories / 55 positions. The new edition ("PN-EN ISO 11465…") is cited by 12 laboratories in 32 positions; 11 of them have no notation of the old edition and the tab will not show them. Over all forms of the core "11465": 61 laboratories / 91 positions.

Method principle

The sample is dried to constant mass at 105 ± 5 °C in a drying oven with forced air circulation; the difference in the mass of the portion of soil before and after drying serves for the calculation of the dry matter and of the water content: w_dm = (m2 − m0)/(m1 − m0)·100 and w_H2O = (m1 − m2)/(m2 − m0)·100 [% m/m], where m0 is the mass of the empty container with its lid, m1 the mass of the container with air-dry or field-moist soil and m2 the mass of the container with dried soil; the result to 0.1 %. The water content referred to the dry matter may exceed 100 %. Soils with a content of organic matter above 10 % (peat soils) are dried at 50 °C (under vacuum if desired), because the decomposition of the organic matter is then no longer negligible; gypsum minerals lose their water of crystallisation at 105 °C, and volatile (organic) substances make a reliable determination of the water impossible. The operations are carried out quickly, in order to limit evaporation, with the light particles protected against draughts.

Applications

• Conversion of the results of chemical analyses of soil to the dry matter (metals, available nutrients, organic carbon)
• Determination of the actual moisture of agricultural and forest soils and of grounds in environmental studies
• Control of the state of samples before physicochemical analyses (ISO 11464)
• Reclamation studies and monitoring of contaminated sites
• A basis for the calculation of the rates of agents and of water balances in field experiments

Key parameters

Standard

Standard number

PN-ISO 11465:1999 (wersja polska; wprowadza ISO 11465:1993 [IDT] i ISO 11465:1993/Cor 1:1994 [IDT])

Title (PL)

Jakość gleby — Oznaczanie zawartości suchej masy gleby i wody w glebie w przeliczeniu na suchą masę gleby — Metoda wagowa

Title (EN)

Soil quality — Determination of dry matter and water content on a mass basis — Gravimetric method

Step-by-step procedure

1. Preparation of the container

   Dry the container with its lid at 105 ± 5 °C, cool it in a desiccator for at least 45 min with the lid closed and weigh it (m0) to an accuracy of 1 mg (air-dry samples) or 10 mg (field-moist ones).

2. Weighed portion

   Air-dry sample (e.g. in accordance with ISO 11464): transfer 10–15 g of soil with a spoon and weigh the closed container with the soil (m1) to 1 mg. Field-moist sample: mix the soil on a glass plate, remove stones and twigs > 2 mm (unless the sample is intended for the analysis of organic micropollutants — then without removal), transfer 30–40 g and weigh it (m1) to 10 mg. Work quickly, in order to limit evaporation.

3. Drying

   Dry the container with the soil, and the lid separately, at 105 °C to constant mass (the check: two weighings after cooling at an interval of 4 h differing by ≤ 0.1 %); protect the light particles against draughts. Dry soils with a content of organic matter > 10 % at 50 °C.

4. Weighing

   Cool the closed container in a desiccator for at least 45 min, take it out and weigh it immediately (m2) to the appropriate accuracy.

5. Calculations and test report

   Calculate w_dm = (m2 − m0)/(m1 − m0)·100 and w_H2O = (m1 − m2)/(m2 − m0)·100 to 0.1 %; check the repeatability of the duplicate determinations. In the test report give the reference to the standard, the identification of the sample, the results, any special features (gypsum, gravel, twigs) and the deviations from the procedure.

Required equipment and apparatus

Health and safety (OHS)

• Samples of contaminated soils: avoid contact with the skin, dry them in a drying oven with an air outlet, so as not to contaminate the atmosphere of the laboratory and other samples
• Take hot containers out with tongs; open the desiccator slowly
• Replace or regenerate the drying agent in the desiccator once it has lost its activity

Frequently asked questions