caliche

noun

1. (countable, uncountable)A crude form of sodium nitrate from South America; used as a fertilizer.
2. (countable, uncountable)A layer of hard clay subsoil or sedimentary rock; hardpan.

   “According to local well drillers, in wells drilled on the high plains a few hundred feet back from the caliche escarpment or in other locations on the high plains in this area no hard caliche or white layer, such as would characterize a soft layer of high lime-carbonate content, is generally reached at a depth corresponding to the elevation of the caliche escarpment.”

   “Having a layer of caliche at depths of 16 inches and less really puts a damper on the garden site. The caliche does not allow roots to penetrate it (tree roots often take 10 years to break through a caliche layer) nor does this mineral allow water to drain.”

   “Caliche in various forms, namely powdery, nodule, tube, fracture-infill, laminar crust, hard laminated crust (hardpan) and pisolitic crust, is widespread in the Mersin area in southern Turkey (Eren et al., 2008; Kadir and Eren, 2008).”