Our EvolvingConceptualModel

This is called“Pw” in the soilscommunity

Plant Available Water

Water Moves from zones ofLow potential (loosely held) to zones of high potential (tightly held)

Water Moves from zones ofLow potential (loosely held) to zones of high potential (tightly held)

Loam @ 15 Pw Sand @ 12 Pw

Which way does theWater move?

Water Moves from zones ofLow potential (loosely held) to zones of high potential (tightly held)

Loam @ 15 Pw Sand @ 10 Pw

State Soil of Iowa

Typic Hapludoll

Well drained

Moderately-welldrained

Somewhat poorlydrained

Poorl

Poorly Drained

(fungi)

grazing

contaminants?

carbon availability

Main Role: C6H12O6 CO2 + H2O

pH

Another major role for soil bacteria:

no transfer of electrons

e-- shiftedFrom N to O2

e-- shiftedFrom N to O2

e-- shiftedFrom CHO to N

e- shifted fromS to O2

e-- shiftedfrom CHO to N

e-- shiftedFrom Fe to O2

e-- shiftedFrom CHO to Fe

H2O

2

+ Fe 3+ + H+

= energy flow and chemical energy storage

SO4

CH4 CO2

ccEricoid

Etc.

Vesicular Arbuscular Mycorrhizae

(

(Circa 1980)

Essential Nutrients for Plants(in addition to C,H,O)

Macronutrients (tens of kg ha-1yr-1 to 100+)

N*P* * Contained in SOMKCaMg

S*

Micronutrients (<1-10 kg ha-1yr-1 )

Mn, Zn, Fe, Cu, Mo, Cl, B, (Se)

Plants exude labile C into the Rhizosphere

Rhizobacteria populationIncreases, and they mineN from soil organic matter

Protozoa and nematode Predators eat theRhizobacteria, Spewing NH3 into the Rhizosphere soil

The basics of a symbiosis betweenplants and rhizosphere organisms:

Plants exude labile C into the Rhizosphere

Rhizobacteria populationIncreases, and they mineN from soil organic matter

Protozoa and nematode Predators eat theRhizobacteria, Spewing NH3 into the Rhizosphere soil

Chemical signals (?)

Farming the rhizosphere to grow bacteria?

Bonkowski 2004

Bonkowski 2004

Essential Nutrients for Plants(in addition to C,H,O)

Macronutrients (tens of kg ha-1yr-1 to 100+)

N*P* * Contained in SOMKCaMg

S*

Micronutrients (<1-10 kg ha-1yr-1 )

Mn, Zn, Fe, Cu, Mo, Cl, B, (Se)

cations anions

RhizobacteriaPotozoaNematodesMycorrhizae

Our model of soilcompartments and the chemical exchangesamong them

N2

N fixers

Removal/harvest

rhizosphere