Land Use & Soil Erosion

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Land Use Soil Erosion

• Agriculture dominant land use
• Urban Sprawl new land use threat
• Excessive soil erosion soil components moved to
  new location due to water or wind

http//www.metacafe.com/watch/yt-x2CiDaUYr90/u_s_d
ust_bowl_of_1930s/
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Type of Erosion

• Geological (natural) Erosion
• continuous slow rate of erosion
• 0.02 to 0.25 mm /yr for bare rock
• 2 mm /yr on stable soil surface

• Accelerated Erosion human-caused
• 10 tons/A/yr
• (natural replacement 0.5 tons/A/yr)
• splash, sheet, rill, gully erosion
• Dust Bowl (1930s)

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Rill Erosion
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Gully Erosion
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Shelterbelt Program

• Response to Dust Bowl

• 1-5 rows of trees (preferable to have 12)

• 70 reduction in wind speed

• Aesthetics, wildlife habitat, energy conservation
  (25 savings)

• Will we repeat History? - removing windbreaks to
  gain gt field size

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Managing Soil Erosion

• USDA 3,000 Soil Water Conservation Districts

• Are we controlling soil erosion?

• rate today rate during 1930s)
• 4 B tons /yr

• mostly on farmland (50 water-based 60
  wind-based)

• 80 farmland gt natural replace. rate

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Tolerable Soil Loss

• USDA erosion loss of 1 to 5 tons/A/yr without
  impacting crop production

• No scientific basis for this measure

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Costs of Soil Erosion

• Lower soil fertility / crop production

• Air (dust) water (sediments) pollution

• Estimates of on-site costs 27 B/yr
• Estimates of off-site costs 17 B/yr

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Erosion Factors (water)

• Rainfall
• Amount, Intensity, Seasonality

• Surface Cover (erodibility)
• Soil structure (related to water-stable
  aggregates)

water-stable aggregates material that aids in
soil particles clumping together in water (e.g.,
organic matter)
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Erosion Factors (water)
cover crops vegetation grown before/after
primary crop for protection of soil surface
(e.g., clover, alfalfa, winter wheat) related
to green manure
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Erosion Factors (water)
green manure plowing under of cover crop in
order to increase soil fertility (N fixation),
increase organic matter, reduce erosion
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Erosion Factors (water)

• Topography
• Slope grade and length

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Controlling Water Erosion of Soil
clean tillage crop residues turned into soil
soon after harvest often fall plow

1. contour farming
2. Strip cropping
3. Terracing
4. Gully reclamation
5. Conservation tillage
6. Cropland Reduction Programs

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Moldboard Plow
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Moldboard Plow
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Contour Farming

• Farming perpendicular to slope (across slope) --
  Jefferson
• Reduces water runoff (65), erosion, and
  siltation

• Link to Strip Cropping

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Contour-Strip Cropping
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Strip Cropping

• Alternate strips of crops across a slope
• Rotate crops (crop rotation), i.e., rotate strips

• Example
• Corn-Oats-Alfalfa

Oats
Alfalfa
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Waterways
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Terracing

• Ancient practice from mountain cultures
• Create bench-like steps on steep slopes
• ridge terraces (broad-base or grass backslope)
  broad flat steps in slope
• channel terraces dig channel across slope used
  in high runoff sites

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Channel Terracing
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Conservation Tillage

• Limit or restrict plowing (tilling) of soil in
  order to reduce soil erosion

• lt 50 of US cropland

1) Minimum Tillage field cultivator disc for
working top few inches of soil (vs. moldboard
plow turning 6 inches)
2) No Till field machinery cuts narrow slit
into soil drops seed maximal surface residue
maximal soil protection
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Minimum Tillage Equipment
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No-Till Farming

• Pros
• - reduces labor, fuel consumption, soil erosion
• - increases crop yield

• Cons
• - need special equipment
• - not universal
• - disease crop pest problems (herbicide
  pesticide use)

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No Till Equipment
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No Till
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No-Till with Crop Residue
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Pesticides
pesticide chemical that kills pests (animal
plant)
herbicide weeds insecticide
insects rodenticide rodents
Silent Spring Rachel Carson (1960s) 1960s to
present (6X gt herbicide)
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No-Till vs. Minimum Till
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Alternative Agriculture Systems
conventional farming agrochemicals, new crop
varieties, bigger equipment
alternative agriculture use organic, biodynamic,
integrated, low-input or no-till concepts
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Alternative Agriculture Systems
organic farming no agrochemicals combats
disease/insects via cultural treatments (e.g.,
crop rotation, green manures, compost)
biodynamic farming use soil preparations made
from animal manure, silica, and plants
low-input farming minimize use of material from
outside of farm
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The Ecology of Farming

• Native communities dynamic equilibrium

• Human-altered systems monocultures, ecosystem
  simplification

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Cutting-Edge Agriculture
Integrated Pest Mgt (IPM) limit pesticide use by
combating insect pests with broad-spectrum
(integrated) approach (e.g., biological,
chemical, cultural)
precision farming use satellites (Global
Positioning System GPS) to map fields and
spatial data (crop yield, fertilizer
application) manage smaller units (i.e., field
sub-units)
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Precision Farming
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Precision Farming
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Soil Properties

• comprised of minerals
• organic matter
• water
• air

• Properties texture, structure, organic matter,
  life, aeration, moisture content, pH, fertility

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Soil Texture

• Coarse fraction (rock, gravel) vs. fine-earth
  fraction (sand, silt, clay)

• Sand gt Silt gt Clay

• textural classes (soil texture pyramid, p.105,
  fig 6.2)

• adsorption process of forming chemical bonds
  (ionic bonds) between nutrients () and soil
  (clay -) relates to leaching/fertility

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Adsorption
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Soil Structure

• arrangement/grouping of soil into aggregates (or
  clumps)

• Influenced by natural physical factors (e.g.,
  freezing/thawing, burrowing) and human
  alterations (e.g., tilling)

• Affects soil permeability (air water) and plant
  growth (roots)

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Soil Organic Matter (OM) Life

• OM living dead organisms in soil

• humus top layer of soil produced via
  decomposition improves structure, permeability,
  stability, fertility, habitat

• microorganisms vs. macroorganisms

• mycorrhizae (pl.) fungus root symbiotic
  relationship between plant fungus nutrient
  uptake from soil (e.g., conifers and fungi)

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Aeration Moisture Content

• pore space space between soil particles filled
  with air or water relation to structure
  texture (sand vs. clay)

• Pore space (aeration/moisture content) increased
  by OM

• At soil saturation, all pores filled with water
  correlated with surface runoff intensity / erosion

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Soil pH (reaction)

• soil reaction pH of soil (acid, neutral, basic)
  depends on H or OH- ions

• wet mesic soils acidic to neutral
• dry soils -- basic

• pH agriculture
• lime (CaCO3) Ca ions reduce acidity
• fertilizers (N, P) with water acidic

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Soil Fertility

• soil fertility capacity to provide all nutrients
  needed for maximum growth

• macronutrient vs. micronutrient
• - N vs Fe

• relation to pH

• some nutrient sources
• fixation, decomposition, animal waste

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Soil Formation
Five Factors

• Climate (temp. precipitation)
• physical chemical changes in soil/rock
  (weathering) clay, leaching

2) Parent material - weathering in place or
transported - outwash plain, alluvial,
lacustrine, dunes, tephra
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Soil Formation
Five Factors
3) Organisms (macro and micro)
4) Topography relation to water movement soil
condition/type
5) Time 4.5 - 3.5 billion yrs before
present(ybp) relation to other 4 factors
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Soil Profile

• soil profile cross-section view of soil horizons

• horizon layers of soil that share attributes of
  texture, structure, etc

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Soil Profile
Major Horizons

• O horizon (organic layer)
• A horizon (topsoil, humus, life)

• E horizon (leaching zone)
• B horizon (subsoil, accumulation zone)

• C horizon (parent material, field stone)
• R horizon (bedrock)

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Water Resources
Water Shortage?
1) Human Population

1. Consumption - ag.,industry,resident

3) Efficiency
4) Distribution Problems
5) Pollution (air, soil, water)
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Water Cycle?
replacement period time to complete cycle (9
days to 37,000 years)

• Unequal distribution of precipitation
• US 102 cm
• MI 81 cm
• Death Valley 4 cm
• Pacific NW 368 cm

• Evaporation Transpiration

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Surface Water Groundwater

• Surface water (lakes, streams)
• may be potable, municipal use

• Groundwater water infiltrates into soil

• percolation into aquifer (porous soil stratum of
  sandstone or limestone)

• zone of aeration plant roots, capillary water in
  pore spaces

• zone of saturation pore filled from water table
  down to bedrock

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Watersheds
watershed area drained stream/river

• U.S. Army Corps of Engineers

Flood Control
1) Levees raise river banks with earthen/stone
dikes

• develop floodplains
• floods prevented, almost
• increase flood severity?

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Flood Control (cont.)
2) Dredging removal of sediments (Corps)
pollutants?
3) Channelization straightening streams (NRCS)
floods drainage, Everglades
4) Dams water impoundment public works
projects

• potable water, irrigation, recreation, energy
• loss of habitat, evaporation, sedimentation,

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Dams

• Alqueva Dam (Portugal)
• Irrigation water but destroys critical habitat
  for Iberian lynx

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• Worlds most endangered cat
• Less than 600
• Spain Portugal

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• Distribution of Iberian lynx

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• Know populations Iberian lynx

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• Alqueva Reservoir began filling February 8th 2002
  behind
• the 96-m-high floodgates
• New proposals to reduce wall height by 13 m
  leading to a
• reduction of the submersed area from 29,636 ha
  to 14,696
• ha.

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Protecting Watersheds Floodplains

• watershed protection as proactive sustainable
  flood control mgt.
• USDA, BLM, Army Corps, TVA

• floodplain zoning Federal Flood Disaster
  Protective Act of 1973
• nonstructural flood control

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Types of Pollution

1. Sediment
2. Inorganic Nutrient
3. Thermal
4. Disease-Producing Microorganisms
5. Toxic Organic Chemicals
6. Heavy Metals
7. Organic Wastes

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Managing Pollution
pollution control (output control) manage
pollutant post hoc - pollutant dispersion
pollution prevention (input control) avoid
pollution a priori
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• Sediment Pollution
• - linked to soil erosion /poor land use

Sources agriculture, logging, construction,
strip mines
Costs 1 million per day in US clog
irrigation canals, hydro- electric turbines,
harbors, life of dams shortened
- carries toxins - turbid water
sedimentation kills coldwater fish/bivalve
habitat
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Controlling Sediment Pollution
- input control includes
conservation tillage contour-strip
farming shelter belts terracing cover
crops/increase OM

• output control includes
• sediment filtration systems (artificial
  natural)
• dredging

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2) Inorganic Nutrient Pollution
- aquatic systems require certain chemical
elements to exist support life

• includes C, O, N, H, P among others
• N P often are limiting factors because of their
  reduced abundance
• P gt N in importance as limiting factor

• gt N P gt productivity of aquatic system

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Lake Productivity Gradient

• oligotrophic nutrient-poor lake
• - low productivity
• - low plant/animal biomass
• - e.g., Lake Superior young lake

2) mesotrophic moderate nutrient base -
swimming, fishing
3) eutrophic nutrient rich - dense algal
blooms - reduced dissolved oxygen, diminished
fishery
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3) Thermal Pollution
- increase temperature of aquatic system

• Harmful effects
• reduced dissolved oxygen
• reduced fish reproduction
• spread of disease

• Benefits
• increase growth rate of some fish
• heating homes

• Use of coolant towers

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4) Disease-Producing Organisms
- infectious organisms introduced to water
cholera, typhoid fever, dysentery, polio,
Cryptosporidium

• better sanitation water treatment can reduce
  disease
• e.g., chlorination for bacteria and oxygenation
  for enteric disease (intestine-dwelling
  anaerobic)

• coliform bacteria count index of
  microorganism-based water pollution
• coliform usually harmless bacteria in human
  gut

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5) Toxic Organic Chemicals
- Carbon-based compounds synthetic derivatives
such as Volatile Organic Compounds (VOCs)
toluene

• Synthetic Organics resist decomposition
  therefore persistent

• Disrupt normal enzyme function in organisms
  interfere with normal chemical reactions in cells

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Water Pollutants
1) Review Table 11.4, p 268 2) Your choice, pick
1 of the pollutants and, a) be able to name it
b) provide an explanation of its use c)
indicate its source its prevalence in the
Great Lakes and d) explain its effects on human
health
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6) Heavy Metals
e.g., lead, mercury, arsenic, cadmium
(fundamental chemical elements)

• Mines contaminated groundwater
• Mines tailings (Clarks Fork of Yellowstone)

• interfere with normal enzyme function

• lead contamination (soil water) from paint
  plumbing pipe (solder)

• mercury contamination (methyl Hg in air water)
  from industry in muscle tissue

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7) Organic Waste reduce available oxygen
- decomposition of wastes by bacteria uses
oxygen release of nutrients -- cyclic

• Oxygen-demanding organic wastes
• biological oxygen demand (BOD) index of amount
  of organic matter in water sample indexed via
  rate of oxygen use by bacteria

• aquatic indicator species (bio-sentinels or
  bio-indicators) also application to other
  pollutants (may flies, trout, bullheads, carp,
  sludge worms, mink)

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7) Organic Waste reduce available oxygen
- decomposition of wastes by bacteria uses
oxygen release of nutrients -- cyclic

• Oxygen-demanding organic wastes
• biological oxygen demand (BOD) index of amount
  of organic matter in water sample indexed via
  rate of oxygen use by bacteria

• aquatic indicator species (bio-sentinels or
  bio-indicators) also application to other
  pollutants (may flies, trout, bullheads, carp,
  sludge worms, mink)

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Eutrophication
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Gulf of Mexico - Watershed
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Gulf of Mexico - Watershed

• hypoxic zone
• dissolved oxygen concentration less than 2 mg/L,
  or 2 ppm

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Gulf of Mexico - Watershed

• 22,000 km2 in mid-summer
• Size of New Jersey or the states of Rhode Island
  and Connecticut combined

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Gulf of Mexico - Watershed