BULK DENSITY EQUATIONS FOR SOUTHERN ALASKA SOILS

A close relationship between organic-carbon content and bulk density was utilized to develop equations for predicting the bulk densities of inorganic soils around the Gulf of Alaska; for example[Formula: see text]where Db is the bulk density (Mg m−3) of fine-earth and OC is the organic carbon content (g kg−1). Adding discrete variables for soil texture (three classes):[Formula: see text]where A is 2.24 for loamy sands, 1.86 for sandy loams, and 1.73 for silt loams. Most of the samples used in developing these equations were from B and C horizons, but they appear to be applicable to other horizons too. They are not valid for (1) horizons with very low organic carbon content (C < 1 g kg−1); (2) organic soils; or (3) disturbed or compacted soils. Coarse fragments (particles > 2 mm) were considered in computing the bulk densities of whole soil horizons, because rock fragments are generally much denser than the bulk fine-earth. Key words: Clod samples, Podzolic soils, Spodosols, organic matter