ultisol

[uhl-tuh-sawl, -sol]
noun
  1. a weathered, red and yellow acidic soil of warm, humid areas that is agriculturally productive when treated with lime and organic fertilizers.

Origin of ultisol

First recorded in 1965–70; ulti(mate) + -sol
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018