5.1 This test method measures the air-filled spaces (porosity) and the moisture-holding capacity of peat on both a mass and a volume basis under conditions of saturation. If large spaces are present, water and air can penetrate easily. If spaces are smaller, the water holding capacity is increased. Water holding capacity is larger in humified peat materials (small inter-particulate spaces) (sapric soil), whereas water and air-penetration is larger in unhumified peat (larger inter-particulate spaces) (fibric soil). The spaces can also be an indication of the oxygen available to the plant roots. As such, the interplay of the properties of moisture holding capacity and porosity dictate the best use of the harvested organic soil material as well as the best management practices for organic soils. The moisture retention relationships of these soils are critical to decisions involving irrigation, drainage, and bearing capacity of these soil.

5.2 Water retention values are particularly important in the management of organic soils. There is much confusion in the literature about the moisture retention values being expressed in various bases; as a percent by volume; as a percent of oven dry mass; or as the percent of the wet mass. In some management decisions, it is necessary to express the water contents of organic soils on a volume basis because of their varied bulk densities, but because of the volume reduction occurring on drying, the water contents must also be expressed on a wet volume basis as collected in the field. Whereas, in other management decisions, moisture retention values are best expressed on a dry mass basis. For example, the difference in mass between the wet and oven dry sample is the moisture held. These values are best expressed on a dry mass basis. Water holding capacities show a marked difference due to the degree of decomposition in an organic soil. The mass of water in fibric soil may be as much as 20 times the mass of the solid particles, whereas that held in a sapric soil contains less than twice the mass. If the water holding capacity is expressed on a volume basis these differences are much less apparent.

1.1 This test method was designed to evaluate the aeration, water penetration, and water retention properties of peat under field conditions of water saturation by measurement of the saturated density, the moisture holding capacity, and the porosity.

1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.

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

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.