Field and laboratory studies of a soil (Solano series) of the lower Sacramento Valley characterize it as a solodized-solonetz. The profile has a sharply delineated, alkaline, fine-textured, columnar B horizon below an acid, medium-textured A horizon. Remnants of an older columnar B horizon persist in the present upper leached portion of the soil.
Soluble salts and free carbonates and much of the clay have been leached from the upper 15 inches of the profile, but are present in appreciable concentrations below this level. Na is the predominant soluble cation. Of the exchangeable bases, Mg is dominant throughout the profile, increasing markedly with depth. Exchangeable Na is low near the surface and increases with depth at a slightly faster rate than does Mg.
Montmorillonite is the predominant mineral of the clay fraction throughout the profile. Kaolin and a small amount of illite are also present throughout. Vermiculite and chlorite, as constituents of the coarse clay fraction (2 to 0.2µ), are concentrated in the A horizons of the profile.
It is concluded that the soil has been altered by solidization as indicated by the sharp boundary between the leached, acid A horizons and the alkaline, fine-textured B horizon containing soluble salts. In its evolutionary past, this soil has been strongly affected by Na and other soluble salts as indicated by the occurrence of older column tops in the present A horizon, distributions of soluble and exchangeable cations and clay, and the distinctive morphology of the profile. At times, salinization, solonization, and solodization have all affected development of this soil. It is doubtful, however, whether it will develop eventually into a true solodi because of the presence of an abundant supply of divalent cations which are being returned annually to the surface by selective plant feeding.