soil- +

(Latin: bottom; under surface; earth, dirt)

solum, true soil (s) (noun); sola, solums; true soils (pl);
The upper layer of a soil profile where the formation of new soil takes place: The solum is where most plant roots and soil animals are found.

The sola, or the top layers of the soil profiles, are affected by climate and vegetation, especially plant roots.

subsoil (s) (noun), subsoils (pl)
The compacted soil beneath the topsoil: Subsoil is between the topsoil and bedrock and consists of humus and broken up and shattered pieces of rock

Cross references of word families related directly, or indirectly, to: "land, ground, fields, soil, dirt, mud, clay, earth (world)": agra-; agrest-; agri-; agro-; argill-; choro-; chthon-; epeiro-; geo-; glob-; lut-; myso-; pedo-; pel-; rhyp-; sord-; terr-.