Soils 4

Front 1

Factors that efffect soil heating from solar energy

Back 1

Aspect, vegetative cover, color/albedo

Front 2

Which soil warms faster - wet or dry?

Back 2

Dry. Wet soil such as in the spring warms more slowly

Front 3

cal/gram of energy need to raise the temperature of water 1 degree, and mineral soil?

Back 3

1 cal/gram H20

.2 cal/gram soil

Front 4

Methods of providing energy for soil cooling through evaporation

Back 4

Solar energy
Soil heat
Long wave radiation from earth

Front 5

Amount of energy needed to evaporate 1 g of water

Back 5

540 g

Front 6

How does heat move through soil?

Back 6

By conduction. From areas of heat(energy) to cooler areas (less energy).

Front 7

Most conductive to least conductive elements of soil

Back 7

Water - Mineral soil - air

Front 8

Paradox of the role water plays in the movement of heat through soil.

Back 8

Water enhances heat transfer through high conductivity but requires more energy to get hot in the first place

Front 9

Describe soil variability

Back 9

Varies by season, depth, location but in predictable patterns. More variable at the surface, lag time for max and min temps.

Front 10

How do humans impact soil temperature?

Back 10

Remove vegetation which broadens extremes. Mixing which removes insulating organic horizons. Buildings and pavement heat up nearby soils. Irrigaion adds H20.

Front 11

Properties of organic and plastic mulches

Back 11

Organic mulches tend to cool the soil and reduce temperature fluctuations. Plastic mulches heat the soil, clear more than black, but black keeps light from causing seed germination.

Front 12

Typical percentages of soil air compared to the atmosphere.

Back 12

Atmosphere is 21% O2 and .03% CO2. Soil air variers from 5-20% O2 and .35 to 10% CO2.

Front 13

Other gases besides O2 and CO2 that are found in soil.

Back 13

N20, H2S, methane - products of organic decomposition - especially anerobic.

Front 14

Why is soil O2 lower?

Back 14

Plant root respiration and limitation on soil air movement

Front 15

The process of soil aeration is

Back 15

the exchange of soil gases with gases in the atmosphere. Release CO2, absorb O2.

Front 16

Two methods of soil aeration

Back 16

Mass flow and Diffusion

Front 17

Mass Flow

Back 17

Bulk movement of air, no gas exchange. Happens mostly in macropores (.08mm or bigger). Rapid.

Front 18

Diffusion

Back 18

Gas exchange from areas of high concentration to low concentration. Happens in both macro and micro pores. Slow. Only method of aeration in micropores

Front 19

Why is soil aeration important?

Back 19

Oxygen is needed by roots and microorganisms to respire and make energy to take up nutrients. As O2 goes down, switch to more anerobic, lower energy reactions, slows decomposition, plant ability to take up nutrients.

Front 20

Key to good soil aeration is

Back 20

Maintaining soil aggregates (macropores) and reducing barriers.

Front 21

Polarity of water

Back 21

Water is slightly positive on H side and slightly negative on O side.

Front 22

Hydrogen bonding

Back 22

Bonding of H side of water to other cations or other water molecules.

Front 23

Cohesion

Back 23

Desire of water molecules to stick together - results from polarity and hydrogen bonding.

Front 24

Adhesion

Back 24

Tendancy of water to stick to surfaces because of polarity - surface tension.

Front 25

Capillarity

Back 25

How water is drawn up a small tube or through small spaces in soil because of cohesion and adhesion. Inverse relationship between height of water and radius of the capilary.

Front 26

Factors effecting soil water movement

Back 26

capilarity and gravity

Front 27

Soil water potential energy

Back 27

Refers to the relative ability of water to do work in soil relative to a reference state of pure water

Front 28

What is the reference state for measuring soil energy potential?

Back 28

Pure water

Front 29

Components of soil water potential

Back 29

Elevation - gravity
Adhesion and cohesion - matric
Dissolved salts - Osmotic potential
Pressure

Front 30

Describe gravity as a component of soil water potential

Back 30

Moves downhill (high to lower energy). Always positive value.

Front 31

Describe matric potential as a component of soil water potential

Back 31

Water bound by cohesion or adhesion has less energy - is a negative value compared to the reference state. Water moves from saturated to unsaturated areas of soil.

Front 32

Types of water flow in soil

Back 32

Saturated and unsaturated. Also vapor -rare.

Front 33

Saturated flow

Back 33

Fast. Happens when all pores filled. Moves with gravity.

Front 34

Unsaturated flow.

Back 34

Slow. Happens when all pores are not filled. Moves laterally and up with capilarity - wet to dry.

Front 35

Saturated vs unsaturated flows in course and fine soil.

Back 35

Course soil quickly gets saturated and flows quickly down. Fine soil takes flows through unsaturated flow for a long time before becoming saturated.

Front 36

Field capacity (FC)

Back 36

When all free water is drained from a soil over a short period time (48 hours). Macropores are empty.

Front 37

Permenant wilting point (PWP)

Back 37

Point where plants are unable to get water from soil. What water remains it too tightly held by adhesion/cohesion.

Front 38

Available water

Back 38

The difference between field capacity and permenant wilting point.