Lactic Acid Fermentation of Human Excreta for Agricultural Application

Soil conditions and plant growth

Edward J. Russell

Soils of the eastern United States and their use--

Jay A. Bonsteel

Elements of agricultural chemistry

Sir Humphry Davy

The nature and properties of soils

Nyle C. Brady

Manual of soil laboratory testing

K. H. Head

Biochar for Environmental Management

Johannes Lehmann

The formation of vegetable mould, through the action of worms

Charles Darwin