Soil & Water Conservation

Benefits of vegetation along streams
-Grasses best on banks
-Trap sediment transported from streams
-Make streams deeper/narrow
-Problem w/ trees is they are big & die, fall in stream destabalizing & causing turbulence.(Large woody debris)
Measurements of Area:
-Acre in feet
-Mile in acres
-Hector in acres
-Acre:43,560sq ft(size of football field including sidelines.
-Mile: 640acres
-Hector: 2.5 Acres
-Kilometer: 0.62 Miles
-Mile: 2.7 km sq
What is texture?
Particle size, sand,silt or clay? determines acquisition, retention, transmittion of water.
How are “peds” held together?
electrochemical bonds & organic gels- they allow for more aeration of water/air, root system growth, porosity.
What is rock gravity density?
2.7 jules, soil is about 1/2 rock so around 1.35 jules.
How much does a cubic ft of water weigh? Soils?
Water=62.4lbs, soil=90lbs
Alluvium vs. Colluvium
Alluvium= material along streambanks.
colluvium= material accumulating on hillsides, didnt make it down to streams.
What is loess?
wind deposited accumulation
What are some soil forming factors? Clorpt equation!
-Climate:MOST IMPORTANT, water makes all chem. & physical reactions possible, too much water= leaching.(30 inches is best amount!), temperature, and wind.
-organisms, includes humans
-relief: the terrain: sunny/shady sides, flood plains etc.
-Parent Material
What is podzolization and where does it occur?
Podzolization= Soils stripped of most nuitrients, white soil: spodisols; occurs in humid regions with excess water.
Why are there no forests in the midwest?
Indians burned them all down.
How did prairies grow in the west? Not enough precipitation.
Ocean moisture.
Types of water erosion
-Sheet: raidrops have large impact when hit move layer of topsoil.
-Rill: gullies small enough to move over.
-Gully: large channels, too big for vehicles to move over
-Stream erosion
Problems of erosion in water
-lost productivity, decrease in aggregates
-exposure of subsoil/loss of topsoil/lack infiltration, fertility.
-Sediment is greatest pollutor of water in world; fills harbors/rivers, costly to dredge; chokes out fish
What is terminal velocity?
More intense the rain/greater size of raindrops= closer to terminal velocity
-Can be decreased by vegetation: directly- interception of leaves, can increase effects in tall canopies, forming very large raindrops easier to reach terminal velocity.
What is pedofauna?
earthworms, ants, termites, bugs, moles, etc.
Structure on effects of raindrops
-Very powerful: Well structured soil can prevent.
-Cementing material
-organic gels
-minerals(calcium carbonate)
What are some wind erosion factors?
-Preponderance: Direction wind is coming from, just one or multiple-Soil structure: strong aggregates, anything larger than 1mm won’t move.
-Surface ridges(furrows): tilled land into ridges reduce velocity, BUT must be correct, can create turbulence if incorrect and increase erosion in tunnels.
-Length of field: longer the stretch, more the erosion
-avalanching: long area creates “Fetching”= creation of waves like that of a deep ocean= more velocity and grip it gets. As soil moves downwind it usually more smooth the further down.
-Vegetative cover: more cover= more windbreak.
-Keep land wet and it wont erode from wind! avoid wilting point!(15 bars)
Who creates soil surveys?
Natural resources Conservation Services.
-started in 1899, mapped soils directly on topography.
-1950-70’s, got mucher better: showed land best for farming, urban development, etc.(class 1_) & land not even good enough to walk on (class 8)
Factors of soil structure: Clay, organic
-Clay: upto 40% clays in soil is beneficial more than that is not.
-Organic material @ a certain concentration can be adverse.
How do streams erode?
-Most erosion occurs on banks of streams when wet, water aquires pore pressure, breaks off easily.
-Floodplains: Usually don’t erode, low slope lots of vegetation.

-Wetter then bank, less the strength
-Grazers can can erode through hooves or eating vegetation on banks.

What is a rip-rap?
Rocks stored along streams to prevent erosion.
What grains get lost in stream erosion?
-Sand is most easily eroded, not large enough to resist or small enough for cohesion.
-Clay: once loses cohesion, lost in water indefinately.
What are the factors of stream power?
-Density: sediment load(minor role)
-Depth: deeper the water more the power.
-multiply all together to find power.
What is avg soil loss tolerance?
2-5 tons/acre-year(T-FACTOR)
–1 ton= 200lbs
-Soil regenerates 1 inch/century!
What are some tolerance factors(T-factors)?
Depth of existing soil
type/depth of parent material
fertility of subsoil- always less fertile than topsoil
What is the universal soil loss equation?
Annual soil loss= rainfall*soil erodibility*angle of slope*length of slope*vegetative cover*conservation.(last two are cultural factors, changable)
Types of wind erosion
suspension: 1/2 mm & smaller suspended in air, can move 1000’s of miles.
Saltation: 1/2 mm and up, bouncing across landscape.
surface creep: 1 mm & larger
Major problems of wind erosion
-fine particles sorted & carried off which can cause major loss of nuitrients.
-Abrasion of plants & materials
-air pollution
What are some factors to crop cover under the annual soil loss equation?
C= crop factor obtained from percent of rain that strikes vegetation before falling on soil surface(Crop canopy), prior land use, surface cover & surface roughness.
X= slope.

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