Bulk Densities of California Soils in Relation to Other Soil Properties

Abstract Analyses of 721 samples from inorganic horizons of upland and alluvial soils in seven orders were utilized to develop equations for predicting soil bulk density at 1/3‐bar water content. The minimum standard errors of estimate (0.14 g cm −3 , r 2 = 0.723, for upland soils and 0.11 g cm −3 , r 2 = 0.672, for alluvial soils) were obtained with functions of organic carbon content, 15‐bar water content, the ratio of 15‐bar water to clay, silt and sand contents, parent material, calcium carbonate equivalent, mean soil horizon depth, and for alluvial soils, soil drainage class too. Functions of electrical conductivity of saturation extract and, for alluvial soils, mean soil horizon depth did not lower the standard errors of estimate (SE) further when added to this list. Organic C content (OC) alone predicts the bulk densities (DB) of upland soils with a SE of 0.19 g cm −3 ( r 2 = 0.462): DB = 1.66 − 0.308 · OC 0.5 .