regions, when the water reaches the B horizon, capillary
action and plant roots then draw it back up toward the
surface, where it evaporates or is incorporated into plant
tissue. After the water escapes, many of its dissolved
ions precipitate in the B horizon, encrusting the soil with
salts. A soil of this type is a pedocal (Fig. 6–17a). This
process often deposits enough calcium carbonate to form
a hard cement called caliche in the soil. In the Imperial
Valley in California, for example, irrigation water contains
high concentrations of calcium carbonate. A thick
continuous layer of caliche forms in the soil as the water
evaporates. To continue growing crops, farmers must
then rip this layer apart with heavy machinery.