5.1 The pH of peat is a useful variable in determining the solubility of minerals, the mobility of ions in the peat, and assessing the viability of the peat-plant environment. pH measurements are made in both test water and a calcium chloride solution because the pH readings in test water can be modified by salts, such as fertilizer material, whereas the observed pH in calcium chloride solution is virtually independent of the initial amount of salts present in the peat. pH values obtained in a calcium chloride solution are usually about a 0.5 to 0.8 pH unit lower than measurements in test water due to release of more hydrogen ions by cation exchange. Both measurements are needed to fully define the character of the peat’s pH.

5.2 pH measurements are used in the agricultural, environmental, geotechnical, and natural resources fields. The pH of peat materials is helpful when evaluating a peat as a topsoil or growing medium for plants.

Note 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

1.1 This test method covers the measurement of the pH of peat materials used as a growing medium. This measurement determines the degree of acidity or alkalinity in peat materials suspended in water and a 0.01 M calcium chloride solution. Measurements in both liquids are necessary to fully define the peat’s pH. This variable is useful in assessing the viability of the peat-plant environment. This test method does not apply to peat that is in paper or construction materials. Test Method D4972 is used for pH testing of soils and Test Method G51 is used for pH testing of soils for corrosion analysis (see Note 1).

Note 1: These three standards are being intentionally kept separate for clarity at the request of the various subcommittees.

1.2 Units—The values given in SI units are to be regarded as the standard. No other units of measurement are included in this standard.

1.3 All measured and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.

1.3.1 The procedures used to specify how data are collected/recorded and calculated, in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.