1. GES 175, Science of Soils Lecture 6, Soil Biology

2. Impact of Macro-organisms

3. Channeling Water

4. Natural Soil Mixing

5. The Little Guys

6. Soil Bacteria

9. Aerobic Organisms Food Source Organic carbon* Ammonium Ion (NH 4 + ) Ferrous Iron (Fe 2+ ) Hydrogen Sulfide (H 2 S) Electron Acceptor Molecular Oxygen (O 2 )

11. Anaerobic Organisms Food Source Organic carbon* Ammonium Ion (NH 4 + ) Ferrous Iron (Fe 2+ ) Hydrogen Sulfide (H 2 S) Electron Acceptor Nitrate (NO 3 - ) Manganese (Mn 4+ ) Ferric Iron (Fe 3+ ) Sulfate (SO 4 2- )

12. legumes Bacterial-Plant Symbiosis

14. - bacteria require plant for growth; plant gains ‘free’ source of available N Nitrogen Fixation * Symbiotic relation between bacteria and plants: -e.g., legumes + rhizobium * Grasses-Azospirillum/Azobactor