What does the word subsoil mean?

Usage examples for subsoil

  1. Hungry- Where the soil contains a considerable portion of gravel, or coarse sand, resting on a gravelly subsoil; on such land manure does not produce the usual effect. – Thomas Davis, Selections from his Prose and Poetry by Thomas Davis Commentator: T. W. Rolleston
  2. Sloping land is by no means always well drained, many hillsides having a subsoil so impervious or so retentive of moisture that under- drainage is a necessity. – Manual of American Grape-Growing by U. P. Hedrick
  3. Grain by grain the subsoil with its fresh mineral ingredients is brought to the surface, and the rich organic matter which plants and animals have taken from the atmosphere is plowed under. – The Elements of Geology by William Harmon Norton