
p. 336 http://books.google.com/books?id=zAhJAAAAMAAJ&pg=PA336; Cited in: Edmund Ruffin An Essay on Calcareous Manures, Volume 1. J.W. Randolph, 1852. p. 85.
Ruffin summarizes:
"Humus" is the term used by this author for the decomposed vegetable and other organic matter which is more or less mixed with all surface soil, and which gives to soil all its fertility, and furnishes all the food of plants.
The Principles of Agriculture, 1844, Section III: Agronomy