. Elementary principles of agriculture; a text book for the common schools . Fig. 49. Poisonous substances in the soil, formed by decaying vegetable matter, some- times keeps a fertile soil from being pro- ductive. (Wheat seedlings grown in: (1) Pure distilled water; (2) soil extract; (3) same soil extract from which the poisonous substances have been removed by absorp- tion with carbon black.) Bureau of Soils, United States Department of Agriculture. (94)

---

Size: 1957px × 2555px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: ., bookauth, bookcentury1900, bookdecade1900, booksubjectagriculture