The Collaborative International Dictionary of English v.0.48:

caliche \ca*li"che\ (k[.a]*l[=e]"ch[-e]), n.
   1. a deposit of sand or clay on the surface containing
      crystallized salts such as sodium chloride or sodium
      nitrate; -- used especially of the sodium nitrate deposits
      of Chile and Peru. --RHUD
      [PJC]

   2. a stratum of calcium carbonate in the soil of an arid or
      semiarid region.
      [PJC]

WordNet (r) 3.0 (2006):

caliche
    n 1: crust or layer of hard subsoil encrusted with calcium-
         carbonate occurring in arid or semiarid regions [syn:
         caliche, hardpan]
    2: nitrate-bearing rock or gravel of the sodium nitrate deposits
       of Chile and Peru