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108 Cards in this Set
- Front
- Back
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2 objectives of soil conservation?
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preserve soil
maintain soils' productivity while using it |
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In what ways is soil erosion spotty & intermittent?
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surface irregularities concentrate erosive effects into certain spots
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What practices increase erosion?
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tilling cropland, grazing, cutting trees, row crops rather than forage crops
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Describe some economic obstacles to soil conservation.
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time lag before investment pays off, short term benefits of not conserving.
Conserving may not benefit them directly and may cost money |
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Describe some aesthetic & cultural obstacles to soil conservation.
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straight rows and zero residues were common and thought to be clean looking/ something you could be proud of)
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Describe some obstacles to soil conservation regarding insecurity, uncertainty and small holdings.
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short term tenants don't reap benefits of investments
unstable climate/politics benefits often go to those downstream **smallholdings are small single family farms- fragment ownership of land/watersheds & make it harder to manage & conserve. |
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Describe some obstacles to soil conservation regarding ignorance & apathy.
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apathy about future needs, shortsighted
effects easily overlooked owners unaware of soil loss. |
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What are the 4 main categories of obstacles to soil conservation?
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ignorance & apathy
economic Aesthetics & culture insecurity, uncertainty and small holdings |
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2 objectives of soil conservation?
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preserve soil
maintain soils' productivity while using it |
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what practices reduce erosion?
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fertilization
multiple cropping (increase cover) forage crops |
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what are some vegetative methods to reducing soil erosion?
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provide denser cover (vegetation) for a greater amount of time.
grassed waterways windbreaks strip cropping |
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what are some mechanical methods to reducing soil erosion?
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contour tillage
no till terracing raprap & other bank protection |
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define stewardship.
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possession & use of land
maintaining the land to be as good when passed on as it was when received |
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What happened in the southern and northern regions of Mesopotamia?
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Fall of Babylon in 539 BC
Northern Mesopotamia suffered from soil erosion, desertification Southern Mesoptamia was ruined by sediment, and saline Cultivation was forced higher up the slopes |
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How did soil erosion increase productivity in Egypt?
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Annual deposits of fine-textured fertile soil: fertile flood plain.
*from deforestation and cultivation up-river |
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List the the 3 major conservation problems in the middle east: Israel, Jordan,Lebanon & Syria.
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cultivating steeper slopes
overgrazing timber harvesting (reduction of protective native cover) |
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List the the 3 major conservation problems in Greece, Italy and North Africa.
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bare soils
Carthage attacked by southern herders: overgrazing & neglect. Cultivating steeper slopes sedimentation caused floods |
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How was arable land increased in the Netherlands & Belgium?
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building dikes,
pumping seawater out (windmills), using river water for reclamation & irrigation |
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What are the most important soil conservation problems in China?
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most of the land has been cleared for cultivation
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Why were American settlers unprepared to handle soil erosion?
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rainfall was greater than in Europe
+ the west was open |
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How has soil erosion changed between 1982 and 2007 in the US?
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decreased about 30%
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How has cropland acreage changed between 1982 and 2007 in the US?
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decreased about 15%
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What was the avg annual soil loss by sheet and rill erosion in 2007?
(tons/acre/year) |
2.7 tons/ac/tr
(4 in 1982) |
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What was the avg annual soil loss by wind erosion in 2007?
(tons/acre/year) |
2.1 tons/ac/year
(3.3 in 1982) |
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Which processes counteract erosion by increasing land elevation?
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deposition
lava flows uplift (tectonic pressures cause inequalities) |
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What is the principle cause of elevation increases?
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uplift
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________is the slow, gravity-driven process by which soil moves across the pediment.
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Mass wasting
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what is mass wasting?
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the slow, gravity-driven process by which soil moves across the pediment.
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Where are the young and old soils found in backwearing and downwearing?
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backwearing:youngest-slopes, oldest footslopes
high elev- younger soils, lower elev, older soils. Downwearing: |
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What is alluvium?
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mixed texture deposits left by flowing water
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what are bottom deposits?
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Lacustrine
Layered fine sediments at the lake bottom |
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What are some wind deposits?
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Loess (fine texture)
Aeolean (sand) volcanic ash |
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What are the 2 glacial deposits?
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glacial till - deposited directly from ice, not layered
glacial outwash- glacial meltwaters, layered |
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At what rate does geologic erosion occur from gently sloping soils?
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0.5 tons/acre/year
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what is dryland?
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DRY FROM YEAR TO YEAR- NEVER CROPLAND
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What is a drought?
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abnormally dry period that reduces crop yields
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what happens to water falling as precip?
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75% evapotranspired
25% infiltration & runoff |
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how is contour cultivation effective?
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furrows across slope trap water, either slowing it or letting it infiltrate
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difference between zingg and level-ridge terracing?
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zingg uses steeper narrower ridges, while level-ride uses more even, gentle ridges
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what is water harvesting?
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The delivery of water to concentrated area to feed thirsty plants
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methods used to harvest water?
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lagoon leveling (even out water dispersion)
catchment & microcatchment microwatershed |
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Ways to reduce evaporation?
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Vegetative mulches: crop residues, forest litter, wood chips.
Reduce soil temperatures. Reduce wind velocity near the soil surface. Reduce water flow to the surface. Other mulches: Gravel, plastic. Forcing water deeper into the soil. Reducing losses from reservoirs. |
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How may summer fallow efficiency be related to saline seeps?
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more deep percolation, excess salts carried downward may resurface down a slope.
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List 6 way to control unnecessary losses of stored soil water
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Antitranspirants (hydrocarbons)
windbreaks/shelterbelts control weeds & volunteers row spacing optimal timing of all operations growing efficient crops |
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main benefits of irrigation?
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opens up otherwise unusable land
increase yields |
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Hazards of irrigation?
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high costs
spread water borne illness erosion salt accumulation |
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what soils may be unsuitable for irrigation?
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steep slopes
shallow soils (<5ft) sandy or clayey high salts |
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what are riparian rights?
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eastern states- nobody owns water
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what is prior appropriation?
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Western states-permits allow special beneficial uses of water
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most important quality of water for irrigation?
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dilution
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how does furrow irrigation work?
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ridges formed during cultivation channel water across field
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how does subsurface irrigation work?
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controlled drainage using tiles or ditches
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How does trickle irrigation work?
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small plastic lines deliver water directly to soil
saline water can be used. |
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define a saline soil
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<15% Na+ ions
but high conductivity |
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define a sodic soil
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(opposite of saline)
>15% Na+ ions (sodium=sodic) but LOW conductivity |
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define saline sodic soils
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>15% Na+ ions (sodic)
& high conductivity (saline) |
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How do you reclaim a sodic soil?
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add gypsum
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How do you reclaim a saline soil?
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leach salts out
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define wetland
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saturated soils + water loving plants (hydrophytic)
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what are some benefits of wetlands?
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certain crops tolerate wet soils
preservation of plant and animal genetic diversity recreation prevent flooding aquifer recharge pollutant removal |
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characteristics of wet soils?
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dark surface, grey subsoil color, high clays and OM, alkalinity
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problems with wet soils & crop production?
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sensitive crops lose <60% yield
denitrification cracked soil |
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difference between surface & subsurface drainage?
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depression/ ditch versus tile (removes when water table is too high)
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maintenance for drainage tile?
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debris and root removal (for tile)
also blockages in tile must be dug up then relaid |
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define marsh
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soft stem vegetation
surface-water fed high in nutrients neutral pH |
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define swamp
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wetland with woody plants and shrubs
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define bog
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peaty, precip fed, low nutrients, acidic
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define fen
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peaty, high nutrients, less acidic, fed from surface & ground
**PEAT distinguishes fens from marshes |
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Purpose of Wetland Reserve Program?
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achieve greatest wetland value, function & habitat
**provide technical & financial support for restoration |
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when a farmer enrolls into the Wetland Reserve Program, what difference does it make between 10 year 30 year or permanent?
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level of financial assistance for easement value & restoration costs
eg. 30 yr 75%, perm- 100% |
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3 stages of erosion by water
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detach
transport deposit |
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list the 4 main types of water erosion
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sheet
rill gully streambank |
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why is the topsoil generally more important than the subsoil?
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plant nutrients
structure for engineering |
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why are falling raindrops so important to erosion?
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they add energy to the particles and displace them.
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what 4 features of slope affect runoff velocity?
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gradient
length shape aspect |
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what kinds of soils don't resist runoff so well?
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sandy
cultivated intensely |
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what soil properties determine its erodibility?
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texture
structure |
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how does vegetation reduce runoff?
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roots hold soil aggregates together, while leaves stabilize and cover soil surface
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what are the 3 principles of water erosion control?
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reduce raindrop impact on soil
reduce runoff velocity and volume increase soil's resistance to erosion |
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____% of the world surface is devoted to Ag.
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50
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define T value
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maximum tolerable soil loss that will allow continuous cropping and maintain soil productivity without requiring additional mngt inputs.
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What are some on site costs?
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adding nutrients
productivity loss machinery wears on B horizons gully erosion= loss of field |
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soil productivity?
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capacity of a soil for producing a specified plant or sequence of plants under a physically defined set of mngt practices
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maintenance of soil productivity depends on ____________& ___________.
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mngt practices
soil & site characteristics |
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Productivity Index- what is the scale?
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0: no productive capacity
1: fully productive soil |
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list some offsite costs of soil erosion.
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eutrophication
hypoxia sediment reduces fish spawning areas &reduce food sources pesticides into environment sediment in harbors (must be dredged) recreation- fishing, swimming |
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processes that accelerate erosion?
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tillage
overgrazing forest cutting traffic development |
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processes of geologic erosion?
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glaciation
land slides large floods natural grazing |
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downwearing leads to a nearly lever ______.
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peneplain
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backwearing leads to a nearly level ____.
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pediment
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dimensions for intensity?
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L/T (depth of water/duration)
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T=100/P where
t=? & P=? |
T=return period in years
P= probablity that the event will occur in a given year is > a given event |
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what does each term mean:
T=N/n(sub)t |
T=return period in years
N= total number of years nt= number of occurances > T year event |
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Define each term:
Qp= CIA |
Qp=peak discharge
C= coefficient for rainfall abstraction I= avg intensity A= watershed area |
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What is time of concentration?
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the time it takes for water to flow from most hydraulically remote point to confluence
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Define the following terms:
Qd= (P-0.2S)^2 (P+0.8S) |
P= rainfall in inches
Qd=runoff depth S= max dist between rainfall" and runoff" |
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define water conservation.. (there are 3 definitions)
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Any beneficial reduction in water loss, use or waste.
A reduction in water use accomplished by implementation of water conservation or water efficiency measures; or, Improved water management practices that reduce or enhance the beneficial use of water. |
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water efficiency inherently reduces _____ _____.
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water demand!
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define water sustainability
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consumption will not lead to the decline or depletion of freshwater resources
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Between the years 1980 and 2000, population in the United States increased by about 50 million, or about 21%. What happened to water use during that period of time?
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IT leveled off!
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US precip range?
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5-100 inches (more in hilo:127) :)
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Define the terms:
A= P- (I + R + E + T + D) |
A= available water
P= precip I= interception R= runoff E= Evap T= transpiration (plants) D = deep percolation |
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How can you reduce transpiration losses (available water)
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manage weeds and volunteer plants
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how to reduce water losses due to deep percolation?
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grow deep rooting crops (alfalfa)
barrier |
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which irrigation method is best for reclaiming a saline soil?
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border irrigation
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humid regions usually employ ___ irrigation.
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sprinkler
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_____ measure water flow with minimal loss of head.
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parshall flumes
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Manning formula uses ___,__ &____ to calculate ______
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hydraulic radius
slope roughness... flow velocity |
