Here are entered works on natural soils. Works on plant growing media which include both natural soils and artificial media are entered under Plant growing media. Works on growing media which do not contain natural soils are entered under Plant growing media, Artificial. Works on growing media for potted plants are entered under Potting soils. --subdivision Soils under individual plants, e.g. Corn--Soils; and headings beginning with the word Soil
--subdivisions Metabolism--Regulation, Secretion--Regulation, and Synthesis--Regulation under individual chemicals and groups of chemicals, e.g. Copper--Metabolism--Regulation; Copper--Secretion--Regulation; Insulin--Synthesis--Regulation; and subdivision Vocalization--Regulation under individual animals and groups of animals, e.g. Mammals--Vocalization--Regulation; Cattle--Vocalization--Regulation
