Soil Hydrology And Aeration

Question 1

Types of Soil Water

Answer 1

Gravitational
Matric=held by small pores
Hygroscopic= bound to mineral lattices, inaccesible to plants

Question 2

Polarity

Answer 2

Unequal charge distribution. Negative oxygen side and positive hydrogen side. Allows water to for bonds

Question 3

Cohesion

Answer 3

Water sticks to itself

Question 4

Adhesion

Answer 4

Water sticks to solid surfaces

Question 5

Vadose Zone

Answer 5

Unsaturated zone, contains soil profile. Part of critical zone.

Undergoes wetting and drying

Question 6

Soil pore types

Answer 6

Macropores allow for quick movement of water and air

Micro pores (capillarity), stores water, moves through adhesion and cohesion

Question 7

Infiltration rate and runoff

Answer 7

Infiltration rate: how quickly water can infiltrate into the soil. Affected by veg cover, texture and structure, participation rate, preexisting moisture

Runoff: 25-40% of precipitation

When it rains:
Runoff
Infiltration
Evapotranspiración
Storage

Question 8

Capillarity

Answer 8

More capillarity in smaller pores! Clays, finer grain souls

Hydrophilic vs hydrophobic influence

Question 9

Water potential

Answer 9

Difference in energy of of soil water and standard water moving through the soil

Total= matric + osmotic+ gravitational+ hydrostatic

Question 10

Matric Potential

Answer 10

Water drawn through soil bc of adhesion to mineral surfaces, cohesion to its self. Capillary movement

Question 11

Osmotic Potential

Answer 11

Attraction of water to solute ions: different concentrations of salt, salts diffuse to equilibrate

Question 12

Gravitational potential

Answer 12

Gravity drawn water movement

Question 13

Hydrostatic potential

Answer 13

Driven by weight of overhead water (when applicable)

Question 14

Evapotranspiration and PET

Answer 14

Evapotranspiration- water evaporated and consumed by plants

Potential Evapotranspiration- how fast water would be lost from a plant+ soil system if water maintained optimal level

Pet=pan evaporation * .65 (modifier that calculates estimated water used by plants, changes based on veg type)

Question 15

Preferential Flow Paths

Answer 15

Water moves along easier pathways until constrained, then explores other options

Stem flow
Macro-pores/cracks

Bypass flow- water ignores flow through capillary pores, missing large portion of soil matrix, until these preferred pores are backed up

Finger flow: finger shaped preferential flow paths, change in textures (fine\coarse)

Question 16

Coarse/fine

Answer 16

Steady consistent wetting front

Question 17

Fine/coarse

Answer 17

Finger wetting front when coarse area is reached

Question 18

Factors of soil aeration

Answer 18

Soil macropores
Soil water content
Consumption by respiration

Question 19

Gasses in soil air vs atmosphere

Answer 19

Oxygen in atmosphere
- ~20%
Nitrogen in atmosphere
-~78%
Co2 in atmosphere
-~ 0.04%

Oxygen in soil air
-<5%-20%
Nitrogen in soil air
~78%
Co2 in soil air
0.04%-10%

Question 20

Biological processes influence on gas

Answer 20

Plant roots and microbial respiration= consume oxygen and release carbon dioxide

Can lower the water table

Question 21

Environmental Significanse of Soil Aeration

Answer 21

Redox
-Ecology: can slow decay
-Acidity impact: oxidation is pH rise, reduction causes pH fall
-toxic components or nutrients can be more available and mobile in different oxidation states

Question 22

pH and redox potential

Answer 22

Higher ph means less redox potential

Lower ph (more acidic) means higher redox potential