Probably the finest, most human soil science text ever written. Russell avoids unnecessary mathematics and obscure terminology. I do not recommend the recent in-print edition, revised and enlarged by a committee.
Smith, J. Russell. Tree Crops: a Permanent Agriculture. New York: Harcourt, Brace and Company, 1929.
Smith's visionary solution to upland erosion is growing unirrigated tree crops that produce cereal-like foods and nuts. Should sit on the "family bible shelf" of every permaculturalist.
Solomon, Stephen J. Growing Vegetables West of the Cascades. Seattle: Sasquatch Books, 1989.
The complete regional gardening textbook.
————————————-. Backyard Composting. Portland, Ore.: George van Patten Publishing, 1992.
Especially useful for its unique discussion of the overuse of compost and a nonideological approach to raising the most nutritious food possible.
Stout, Ruth. Gardening Without Work for the Aging, the Busy and the Indolent. Old Greenwich, Conn.: Devin-Adair, 1961.
Stout presents the original thesis of permanent mulching.
Turner, Frank Newman. Fertility, Pastures and Cover Crops Based on Nature's Own Balanced Organic Pasture Feeds. San Diego: Rateaver, 1975. Reprinted from the 1955 Faber and Faber, edition.