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Our Evolving Conceptual Model

Our Evolving Conceptual Model. This is called “ Pw ” in the soils community. Plant Available Water. Water Moves from zones of Low potential (loosely held) to zones of high potential (tightly held). Water Moves from zones of

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Our Evolving Conceptual Model

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  1. Our Evolving Conceptual Model

  2. This is called “Pw” in the soils community

  3. Plant Available Water

  4. Water Moves from zones of Low potential (loosely held) to zones of high potential (tightly held)

  5. Water Moves from zones of Low potential (loosely held) to zones of high potential (tightly held) Which way does the Water move? Sand @ 12 Pw Loam @ 15 Pw

  6. Water Moves from zones of Low potential (loosely held) to zones of high potential (tightly held) Loam @ 15 Pw Sand @ 10 Pw

  7. State Soil of Iowa Typic Hapludoll Well drained

  8. Moderately-well drained

  9. Somewhat poorly drained

  10. Poorly Drained Poorl

  11. (fungi)

  12. Main Role: C6H12O6 CO2 + H2O grazing contaminants? pH carbon availability

  13. Another major role for soil bacteria:

  14. no transfer of electrons e-- shifted From N to O2 e-- shifted From N to O2 e-- shifted From CHO to N

  15. e-- shifted from CHO to N e- shifted from S to O2

  16. e-- shifted From Fe to O2 e-- shifted From CHO to Fe

  17. = energy flow and chemical energy storage 2 H2O + Fe 3+ + H+ SO4 CO2 CH4

  18. Ericoid c c Etc.

  19. Vesicular Arbuscular Mycorrhizae (

  20. (Circa 1980)

  21. Essential Nutrients for Plants(in addition to C,H,O) Macronutrients (tens of kg ha-1yr-1 to 100+) N* P* * Contained in SOM K Ca Mg S* Micronutrients (<1-10 kg ha-1yr-1 ) Mn, Zn, Fe, Cu, Mo, Cl, B, (Se)

  22. The basics of a symbiosis between plants and rhizosphere organisms: Plants exude labile C into the Rhizosphere Rhizobacteria population Increases, and they mine N from soil organic matter Protozoa and nematode Predators eat the Rhizobacteria, Spewing NH3 into the Rhizosphere soil

  23. Plants exude labile C into the Rhizosphere Rhizobacteria population Increases, and they mine N from soil organic matter Chemical signals (?) Protozoa and nematode Predators eat the Rhizobacteria, Spewing NH3 into the Rhizosphere soil

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