Soils 101- Exam 2

sodium hexametaphosphate

chemical added to defloculate clay particles

velocity of a particle falling through a liquid

Stokes Law

less porosity

large pores =

2.65 g/cm3

common particle density

1.33 g/cm3

common bulk density

0

kPa at Saturation

-33

kPa at Field Capacity

-1500

kPa at Wilting Point

adhesion, cohesion

Matric potential

movement of water due to solute concentration

Osmotic potential

Saturated flow

the rapid movement of water through macropores

Unsaturated flows

the slow movement of water in thin films

saturated flow and pressure

Darcy's Law

Al Mg

Centrally coordinated cation of Octahedron

Si

Centrally coordinated cation of Tetrahedron

The substitution of one element for another

Isomorphous substitution

Internal surface area

area exposed between the individual crystal layers

External surface area

area exposed on top, bottom, sides

1:1 Phyllos Clay

low CEC, low (-) charge, External surface area, strong H-bond, no expanding

2:1 Mica

low CEC, nonexpanding, K+ binding agent

2:1 Vermiculite

high CEC, semi-expanding, internal surface area

2:1 Smectite

high CEC, fully expanding, both surface areas, high substitution

Allophane and Imogolite

very reactive, high CEC, high water holding capacity

Fe and Al oxides

slightly (-) to moderately (+) charge, low CEC

Humus

contains carboxyl groups, high CEC, high water holding capacity, noncohesive

charge imbalance brought on by isomorphic substitution

Permanent charge

protonation and deprotonation based on solution

pH dependent charge

permanent charge

Phyllosilicate clays are dominated by

pH dominant charge

Kaolinite, Fe & Al oxides, Humus, Allophane are dominated by

Two main sources of CEC

permanent and pH dominant charge

stronger attraction

smaller hydrated charge =

2:1 clays

Mild weathering, frozen or desert

1:1 clay

Moderate weathering- SE US

Fe/Al oxides

Extreme weathering- equator