Exam 2

There are____ USDA textural classes that got from course to fine

12

What is the course fraction?

Particles larger than 2mm

What is NOT soil, or part of soil texture?

The Course fraction

What is SSA?

Specific Surface area

What is Specific surface area?

The amount of particle surface area exposed and available for chemical and physical processes per unit mass or volume of soil

The finer the particle size the ______ the specific surface area

larger

When managing course textures will you need to irrigate and fertilize more?

Yes

T/F: There is MORE runoff with course textured soils

False

T/F: Course textured soils are VERY permeable

True

T/F: There is high run off in fine textures soils

True

T/F: Fine texture soils are Very Permeable

False

Name the structural classes

Structureless 0

Weak 1

Moderate 2

Strong 3

Peds are made up of ________

Aggregates

Aggregate stability

Ability of aggregate to resist applied force

T/F: The higher the organic matter content the LOWER the stability

False

Slaking

Breakdown of air dry soil

Is high mean aggregates preferred?

Yes

What is consistence?

A term used by soil scientists to describe how easily the soil is reshaped or ruptured. Measured by attempting to squeeze a ped between fingers or underfoot.

What is consistence affected by?

The amount of clay

What is consistency?

A term used by engineers to describe soil resistance to penetrations by an object. Measured by attempting to penetrate the soil with a blunt pencil or penetrometer

What is soil strength?

Defined by engineers as the capacity of a soil mass to withstand stress, without rupturing or becoming deformed

Particle Density (Dp)

density of soil solids alone (volume of pores not included)

What is the density calculation

Mass/Volume

Soil density is expressed n what 2 ways?

Particle and Bulk density

What is the go to number to calculate particle density?

2.65 g/cm³ - Quartz

What is bulk density?

Density of the soil including pore space.

T/F: Bulk density is a static property

False

As bulk density increases…

so does soil strength and pore space decreases

Soil porosity

indicates ho much of the total soil volume is pore space - decimal or percentage

Porosity on non compacted medium textured soils will be about

~50% pore space

Porosity _____ have units

does not

Hydrolic conductivity

Physical parameter that relates to the ability of the soil to allo water to pass or permeate through it

The higher the pore space the ______ the conductivity

higher

Percolation

The downward movement of water through the soil profile

Leaching

Removal of material from the soil as percolating water (moving downward) moves down through pores

The lower the temperature of the soil the _______ the microbial activity.

lower

Typically, the higher the temperature the more nutrients is lost through ______

leaching

Heat Capacity

The amount of each energy required to change the temperature by 1C

It takes ____x more energy to warm water than an equal volume of air.

3000x

Urban Soils

Originally used for a natural purpose, then formed for an urban use

What is the proposed 13th soil order?

Artesols - from latin phrase arte factum - made with skill/art

What is defined as an artesol?

Intentional human activity

Cohesion

water clinging to itself through weak hydrogen bonding - surface tension

Adhesion

Water clinging to other surfaces, results in meniscus tubes

Capillarity is a result of

cohesion and adhesion

Capillarity

the tendency of water to climb in a space

Water content controls

soil air content and temperature

water makes up __% of green plant tissue and microbial bodies

70%

List the soil water contents from highest to lowest water content

Saturation
Feild Capacity
Permanent wilting point
Oven dry

Saturation aka Maximum retentive capacity

All soil pores filled with water

Feild Capacity

Water left after gravitational water has drained

When does the soil hit feild capacity?

occurs 2-3 days after rain/irrigation event has saturated the soil

Gravitational water is considered

unavailable for plant use

Permanent Wilting Point (PWP)

Quantity of water so low that plants growing in that soil will wilt beyond recovery

Weathering

involves wearing away of rocks/parent materials

Erosion

involves wearing away of already formed soil and movement of that soil elsewhere

What are the steps of Erosion

1. Detachment

2. Transport

3. Deposition

Overgrazing causes about ___% of soil loss

35%

Deforestation causes about ___% of soil loss

30%

Mismanagement of cultivated lands causes about __% of soil loss

28%

Splash Erosion

detachment of particles by forcing of falling drops of water

What is the most important type of erosion to control?

Splash Erosion

Sheet Erosion aka Interill Erosion

Detachment and transport of soil particles in a thin layer or sheet by surface water run off

What is the most common type of water erosion and takes up about 70% of processes?

Sheet erosion

Rill/Gully Erosion

Creation of cuts through soil due to surface runoff, gaining velocity which detaches more particles

Which is bigger, rill or a gully?

Gully

Stream erosion

Erosion along the banks of streams

Cover Cropping is a form of cultural erosion control that limits _________

detachment, slows runoff, promotes infiltration, and maintain soil temperature

Mulching is the same as _______ _______ but with w/ non-living material

cover crops

Proper _______ of cultivation can help prevent erosion

timing

You should plow when wet

False

You should not plow before a wet event

True

You should plow as far in advance in possible

False

Conservative Tillage

Any tillage that reduces loss of soil or water relative to conventional tillages

Conservation Tillage leaves about __% of the soil surface covered by residues

30%

Contour Cultivation

Plowing and/or planting along the natural curvature of the land

Addition of soil conditioners, what are soil conditioners?

organic matter and lime/gypsum

What does adding soil conditioners do to soil?

Improves infiltration and reduces runoff

What does contour cultivation do?

Slows run off and promotes on site deposition

Rip Rap

Use of large angular blocks on the bottom or side of channels where high velocities are expected

Stream bank erosion may be __% or more of total soil loss in some watersheds

40%

Terracing

Stair like surface manipulation to reduce down-slope runoff velocity and encourage retention of sediments

Bioengineering

The use of vegetation to protect channels, reduce down-slope runoff velocity and trap sediments

Sediment Traps

Materials (usually temporary) designed to slow down run-off and trap sediments (Silt fences, wattles etc.)

Retention Ponds

Ponds constructed down-slope of a field which collects runoff and allows sediments to settle before movement of water offsites

What is the three step process for both water and wind erosion?

1. Detachment

2. Transportation

3. Deposition

How does wind velocity affect erosion?

Threshold velocity is required to initiate wind erosion

___mph at 2 meters above the surface to initiate erosion

18mph

How do soil properties affect wind erosion?

Moisture content, areas with low annual rainfall are most vulnerable

How does soil roughness affect wind erosion?

The rougher the surface, the less severe the erosion

Saltation

Movement of soil by a series of short bounces along the ground

Saltation is only abou __cm high

30cm

Saltation accounts for %-% of soil movement

50% - 90%

Saltation are _____ sized particles. 0.1-0.5mm in diameter

Intermediate

Soil Creep

Movement of soil by rolling and sliding along the surface of larger particles (0.5 to 2mm diameter)

Suspension

Dust particles of fine sand sized and smaller (<0.1mm diameter) are moved parallel to the ground surface

Functional Redundancy

The presence of several organism to carry out each task, leads both ecosystem stability and resilience

Earthworms

Hastens teh cycling and increases the availability of mineral nutrients leaves soil borings

Microfauna - Nematodes

Some are pests

Microflora - Archaea

Domain of organisms previously classified as bacteria - Methanogens