Fiber Size Distribution, Bulk Density, and Ash Content of Peats in Minnesota, Wisconsin, and Michigan

Abstract

AbstractBoelter (1969) described the physical characteristics of some undrained organic soils in northern Minnesota. This paper expands upon Boelter's work. Bulk density, ash content, and percent (dry weight basis) of rubbed and unrubbed fiber > 2.0 mm, 1.0 – 2.0 mm, 0.5 – 1.0 mm, 0.25 – 0.5 mm, and 0.1 – 0.25 mm were determined for 176 peat samples from 38 peatlands in northern Minnesota, Wisconsin, and the Upper Peninsula of Michigan. When the distribution of various sizes of plant fibers in the peat is used as an index of the stage of peat decomposition, the increase in bulk density that accompanies increasing decomposition is easily seen. Fibers > 0.5 mm predominate in low bulk density peats, but are quickly lost as decomposition proceeds and bulk density increases. Curvilinear regression equations between bulk density and rubbed and unrubbed fiber >0.5, >0.25 and 0.1 mm were developed that represent improvements over such equations previously calculated for northern Minnesota peats only. At the same bulk density, moss peats contained larger amounts of fiber than herbaceous peats; the unrubbed fiber content of the woody peats studied was higher than that of moss peats, but fell to an intermediate level between moss and herbaceous peats when subjected to rubbing. When a dispersing agent such as sodium metaphosphate (NaPO3) is used before sieving and percent fiber is calculated on a dry weight basis, the traditional rubbed fiber content appears to have little advantage over unrubbed fiber content as a descriptive criterion for characterizing organic soil.