| Soils, Crops and Fertilizer Use |
|Chapter 9: Using chemical fertilizers|
As opposed to organic fertilizers which originate from plants and animals (compost, manure, etc.) or are unprocessed minerals like raw rock phosphate, chemical fertilizers are derived from a chemical manufacturing or synthesizing process. Some examples are urea fertilizer (45-46 percent N) made from carbon dioxide and ammonia, or single superphosphate 18-21 percent P2O5) made from combining rock phosphate and sulfuric acid.