Document

Report
Ch 9
Soil and Agriculture
Part 2: Environmental Issues
and the Search for Solutions
PowerPoint® Slides prepared by
Jay Withgott and Heidi Marcum
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Lecture Outlines
Chapter 9
Environment:
The Science behind the
Stories
4th Edition
Withgott/Brennan
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 1: Review
Traditional subsistence agriculture uses all of the following,
except:
a) Animal power
b) Irrigation
c) Irrigation water
d) Fossil fuels
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 2: Review
Physical weathering is characterized by:
a) The chemical interaction of water with parent
material
b) Organisms breaking down parent material
c) Wind or rain breaking down parent material
d) The dislodging or movement of soil by wind
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 3: Review
Erosion increases through all of the following, except:
a) Excessive tilling
b) Overgrazing
c) Clearing forests
d) All of the above increase erosion
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 4: Review
Which sustainable farming method involves planting rows
of trees along field edges to slow the wind?
a) Terracing
b) Crop rotation
c) Shelterbelts
d) Contour farming
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 5: Interpreting Graphs and Data
According to this figure, which of the following is NOT true?
a) Reduced tillage
results in less nitrogen
loss
b) Conventional tillage
causes more soil loss
c) Organic carbon lost
is greater with reduced
tillage
d) Conventional and
reduced tillage have few
differences
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 5: Interpreting Graphs and Data
According to this figure, which of the following is NOT true?
a) Reduced tillage
results in less nitrogen
loss
b) Conventional tillage
causes more soil loss
c) Organic carbon lost
is greater with reduced
tillage
d) Conventional and
reduced tillage have few
differences
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
This lecture will help you understand:
• The relationship between
soils and agriculture
• Major agricultural
developments
• The fundamentals of soil
science
• Causes and consequences
of soil erosion and
degradation
• Principles of soil
conservation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
No-till agriculture in Iowa
• Repeated plowing and
planting damage soil
• No-till farming
- Benefits the soil
- Saves time and money
• Other conservation measures:
- Careful use of fertilizers
- Preventing erosion
- Retiring fragile soils
• Production is not lowered
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Soil: the foundation for agriculture*
• Land devoted to agriculture covers 38% of Earth’s land
surface
• Agriculture = practice of raising crops and livestock for
human use and consumption
• Cropland = land used to raise plants for human use
• Rangeland or pasture = land used for grazing livestock
• Soil = a complex plant-supporting system consisting of
disintegrated rock, organic matter, water, gases, nutrients,
and microorganism
- It is a renewable resource
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Population and consumption degrades soil*
• Feeding the world’s rising human population requires
changing our diet or increasing agricultural production
• Land suitable for farming is running out
• We must find ways to improve the efficiency of food
production
• Mismanaged agriculture turns grasslands into deserts;
removes forests; diminishes biodiversity; and pollutes
soil, air, and water
- Fertile soil is blown and washed away
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Millions of acres of cropland are lost each
year
We lose 5-7 million ha (12-17 million acres) of
productive cropland annually
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Soil degradation has many causes*
• Soil degradation results
from deforestation,
agriculture and
overgrazing
• Over the past 50 years,
soil degradation has
reduced global grain
production by 13%
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Agriculture arose 10,000 years ago*
• Agriculture was invented independently by different cultures
• The earliest plant and animal domestication is from the
“Fertile Crescent” of the Middle East
- Wheat, barley, rye, peas, lentils, onions, goats, sheep
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Traditional agriculture*
• Traditional agriculture = biologically powered
agriculture, using human and animal muscle power
- Subsistence agriculture = families produce only
enough food for themselves
- Intensive agriculture = produces excess food to sell
- Uses animals, irrigation and fertilizer, but not fossil
fuels
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Industrialized agriculture is a recent
phenomenon*
• Industrialized agriculture = using large-scale
mechanization and fossil fuels to boost yields
- Also uses pesticides, irrigation and fertilizers
- Monocultures = uniform planting of a single crop
• Green revolution = the use of new technology, crop
varieties and farming practices introduced to developing
countries
- Increased yields
- Created new problems and worsened old ones
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Soil as a system*
• Soil consists of mineral
matter, organic matter,
air, and water
- Dead and living
microorganisms, and
decaying material
- Bacteria, algae,
earthworms, insects,
mammals,
amphibians, and
reptiles
Since soil is composed of living and non-living matter, it is
considered an ecosystem
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Soil formation is slow and complex*
• Parent material = the base geologic material of soil
- Lava, volcanic ash, rock, dunes
- Bedrock = the continuous mass of solid rock
comprising the Earth’s crust
• Weathering = the physical, chemical, or biological
processes that break down rocks to form soil
- Physical (mechanical) = wind and rain, no chemical
changes in the parent material
- Chemical = substances chemically interact with
parent material
- Biological = organisms break down parent material
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Weathering produces soil
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Other processes affect soil formation*
• Erosion = the dislodging and movement of soil by wind
or water
- Occurs when vegetation is absent
• Biological activity includes deposition, decomposition,
and accumulation of organic matter
- Humus = a dark, spongy, crumbly mass of material
formed by partial decomposition
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Key processes in soil formation
• Key processes in forming soil: weathering and the
accumulation and transformation of organic matter
• They are influenced by the following factors:
- Climate: soils form faster in warm, wet climates
- Organisms: plants and decomposers add organic
matter
- Topography: hills and valleys affect exposure to sun,
wind, and water
- Parent material: influences properties of resulting soil
- Time: soil can take decades to millennia to form
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Soil formation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
A soil profile consists of horizons*
• Horizon = each layer of soil
• Soil profile = the cross-section
of soil as a whole
• Up to six major horizons may
occur in a soil profile
- Topsoil = inorganic and
organic material most
nutritive for plants
- Leaching = dissolved
particles move down through
horizons
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Soils are characterized in many ways
• Soils are classified based on color, texture, structure, and
pH
• Soil color = indicates its composition and fertility
- Black or dark brown = rich in organic matter
- Pale gray or white = indicates leaching
• Soil texture = determined by the size of particles
- From smallest to largest = clay, silt, sand
- Loam = soil with an even mixture of the three
- Influences how easy it is to cultivate and let air and
water travel through the soil
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Soil structure and pH
• Soil structure = a measure of soil’s “clumpiness”
- A medium amount of clumpiness is best for plants
- Repeated tilling compacts soil, decreasing its waterabsorbing capabilities
• Soil pH = affects a soil’s ability to support plant growth
- Soils that are too acidic or basic can kill plants
- pH influences the availability of nutrients for plants
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Nutrient availability
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Regional differences in soils affect
agriculture
• Rainforests have high primary
productivity, but the nutrients are
in plants, not the soil
- Rain leaches minerals and
nutrients deeper into the soil,
reducing their accessibility to
roots
- Swidden agriculture =
cultivation of a plot for a few
years and then letting it regrow
into forest
• Temperate grasslands have lower
rainfall and less nutrient leaching
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Differences in regional agriculture
• Swidden agriculture is not
sustainable at high
population densities
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• Dead plants return
nutrients to the soil on the
Iowa prairie
Erosion degrades ecosystems and
agriculture
• Deposition = the arrival of eroded material at its new
location
• Flowing water deposits sediment in river valleys and
deltas
- Floodplains are excellent for farming
• But, erosion is a problem because it occurs faster than
new soil is formed
• Erosion increases through: excessive tilling, overgrazing,
and clearing forests
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Soil erodes by several methods*
• Plants protect soils form erosion
- Removing plants accelerates erosion
• Rill erosion moves the most topsoil, followed by sheet
and splash forms of erosion
• Water erosion occurs most easily on steep slopes
• Erosion in the U.S. declined between 1982 and 2001
- Soil conservation measures
Despite conservation measures, the U.S. still loses 6 tons of soil
for every ton of grain harvested
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Various types of soil erosion*
Splash
Sheet
Rill
Gully
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Erosion removes soil
• Water erosion removes soil from farmlands
- Erosion in the U.S. has declined due to soil
conservation measures
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Soil erosion is a global problem
• Humans are the primary cause of erosion
- It is occurring at unnaturally high rates
• In Africa, erosion over the next 40 years could reduce
crop yields by half
- Coupled with rapid population growth, some observers
describe the future of agriculture as a crisis situation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Desertification*
• Desertification = a loss of
more than 10% productivity
- Erosion, soil compaction,
forest removal,
overgrazing, salinization,
climate change, depletion
of water sources
• Most prone areas = arid and
semiarid lands
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Desertification has high costs*
• Desertification affects 1/3 of the planet’s land area
- In over 100 countries
• Costs tens of billions of dollars each year
- China loses over $6.5 billion/year alone from goat
overgrazing
- In Kenya, 80% of he land is vulnerable to
desertification from overgrazing and deforestation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Dust Bowl*
• In the late 19th and early
20th centuries, settlers
arrived in Oklahoma,
Texas, Kansas, New
Mexico and Colorado
• Grew wheat, grazed cattle
- Removed vegetation
• A drought in the 1930s
made conditions worse
• Thousands of farmers left
their land and had to rely on
governmental help
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The Soil Conservation Service
• Started in 1935, the Service works with farmers to
develop conservation plans for farms
- Assess the land
- Prepare an integrated plan
- Work closely with landowners
- Implement conservation measures
• Conservation districts = districts operate with federal
direction, authorization, and funding, but are organized
by the states
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Conservation districts
• Districts implement soil conservation
programs to empower local residents
to plan and set priorities
• Natural Resources Conservation
Service = 1994 renaming of the Soil
Conservation Service
- Expanded responsibilities include
water quality protection and
pollution control
- Serves as a model for efforts
around the world
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
International soil conservation efforts
• The SCS and NRCS serve as models for efforts around
the world
• A large part of Argentina, Brazil, and Paraguay uses notill farming
- Resulting from grassroot farmers’ organizations
- Helped by agronomists and extension
agents
An extension agent helps a
farmer grow yucca plants in
Colombia, South America
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Protecting soil: crop rotation and contour
farming*
• Crop Rotation = alternating the
crops grown field from one
season or year to the next,
- Cover crops protect soil when
main crops aren’t planted
- Wheat or corn and soybeans
• Contour Farming = plowing
furrows sideways across a
hillside, perpendicular to its
slope, to prevent rills and gullies
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Protecting soil: terracing and intercropping
• Terracing = level platforms
are cut into steep hillsides,
sometimes with raised edges
- A “staircase” to contain
water
• Intercropping = planting
different types of crops in
alternating bands or other
spatially mixed arrangements
- Increases ground cover
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Protecting soil: shelterbelts and reduced
tillage
• Shelterbelts (windbreaks) =
rows of trees planted along
edges of fields
- Slows the wind
- Can be combined with
intercropping
• Conservation tillage =
reduces the amount of tilling
- Leaves at least 30% of
crop residues in the field
- No-till farming disturbs
the soil even less
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Conservation tillage saves soil
• It increases organic matter and soil biota
- Reducing erosion and improving soil quality
• Prevents carbon from entering the atmosphere
• Reduces fossil fuel use
• But may increase use of herbicides and fertilizers
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Pros and cons of no-till farming
• Almost half of U.S. farmland
uses no-till farming
• Benefits: reduced soil
erosion, greater crop yields,
enhanced soils
• Negatives: increased use of
herbicides and fertilizers
• But, green manure (dead
plants and fertilizer) and
rotating crops minimizes the
negatives
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Plant cover reduces erosion*
• Eroding banks along creeks and
roadsides are stabilized by
planting plants to anchor soil
• China has the world’s largest treeplanting program
- It does slow erosion
- But it does not create
ecologically functional forests,
because monocultures are
planted
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Irrigation: boosted productivity, but
problems, too*
• Irrigation = Artificially providing
water to support agriculture
- Unproductive regions become
farmland
• Waterlogging = over-irrigated
soils
- Water suffocates roots
• Salinization = the buildup of salts
in surface soil layers
- Worse in arid areas
Salinization inhibits production of 20% of all irrigated cropland,
costing more than $11 billion/year
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Salinization prevention*
• It is easier and cheaper to
prevent salinization than fix
it
• Do not plant water-guzzling
crops in sensitive areas
• Irrigate with low-salt water
• Irrigate efficiently,
supplying only water that
the crop requires
- Drip irrigation targets
water directly to plants
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fertilizers boost yields but cause problems*
• Fertilizer = substances that contain essential nutrients
• Inorganic fertilizers = mined or synthetically manufactured
mineral supplements
• Organic fertilizers = the remains or wastes of organisms
- manure, crop residues, fresh vegetation
- Compost = produced when decomposers break down
organic matter
Applying
synthetic
fertilizer, vs.
Planting rye,
a “green
manure”
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Overapplication of Fertilizer*
• Inorganic fertilizer use has
skyrocketed
• Overapplying fertilizer can
ruin the soil and severely
pollute several areas
• Runoff causes eutrophication
in nearby water systems
• Nitrates leach through soil and
contaminate groundwater
• Nitrates can also volatilize
(evaporate) into the air
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Environmental effects of over-fertilizing*
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Overgrazing causes soil degradation*
• Overgrazing = too many
animals eat too much of the
plant cover
- Impedes plant regrowth
• A leading cause of soil
degradation
• Government subsidies
provide few incentives to
protect rangeland
70% of the world’s rangeland is classified as degraded
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Effects of overgrazing can be striking
• Erosion increases, making it hard for plants to grow
• Non-native invasive species invade
- Less palatable to livestock
- Outcompete native vegetation
Grazed plot
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Ungrazed plot
Forestry impacts soil
• Along with farming and
ranching, forestry impacts soils
• Clear-cutting = the removal of
all trees from an area at once
- Leads to soil erosion,
especially on steep slopes
• Modern methods remove fewer
trees over longer periods of time
- Minimizes soil erosion
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
U.S. programs promote soil conservation
• Food Security Act of 1985: Farmers that adopt soil
conservation plan receive price supports and other
benefits
• Conservation Reserve Program (1985)
- Farmers are paid to place highly erodible land into
conservation reserves
- Trees and grasses are planted instead of crops
- Saves 771 million tons of topsoil per year
- Generates income for farmers
- Provides habitat for native wildlife
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Federal Agricultural Improvement Act
(1996)
• Known as the Freedom to Farm Act
- Aimed to reduce subsidies and government influence
over farm products
- Created the Environmental Quality Incentive Program
and Natural Resource Conservation Foundation
- Promotes and pays for conservation practices in
agriculture
• Low-Input Sustainable Agriculture Program (1998)
- Provides funding for sustainable agricultural practices
for individual farmers
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
International soil conservation programs
• Food and Agriculture Organization (FAO) = the United Nations’
main agricultural program
• The FAO’s Farmer-Centered Agricultural Resource
Management Program (FAR)…
- Helps farmers duplicate agricultural success stories
- Uses local communities to educate and encourage farmers to
conserve soils and secure the food supply
- Supports innovative approaches to resource management and
sustainable agriculture in around the world
- China, Thailand, Vietnam, Indonesia, Sri Lanka, Nepal
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Conclusion
• Programs in the U.S. and the world have been successful
in reducing topsoil erosion
• These programs require:
- Research, education, funding, and commitment from
farmers and governments
• To avoid a food crisis caused by population growth, we
need
- Better technology
- Wider adoption of soil conservation techniques
- To consider Aldo Leopold’s land ethic program
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The buildup of salts in soils as a result of
over irrigation is:
• A. Salinization
• B. Leaching
• C. Erosion
• D. Evaporation
• E. Weathering
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During most of human’s 100,000 year
existence and up until 10,000 years ago
• A. we depended upon hunting
• B. we depended upon crops
• C. we depended upon cattle
• D. we depended upon hunting and gathering
• E. we depended upon crops and cattle
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Factors involved in soil formation:
• A. tropical climate, acid precipitation, frequent wildfires
• B. seasonal changes in the tides
• C. nitrogen-fixing bacteria, grazing by herbivores
• D. weathering of parent material, freezing/thawing,
growth of tree roots
• E. erosion, level terrain, absence of rooted vegetation
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True or false
• Organic fertilizers can cause environmental damage even
if used properly
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The consequences of overfertilization can
include:
• A. eutrophication in nearby waters
• B. large crop yields per acre
• C. crops spreading rapidly into nearby areas
• D. very futile soils in future years
• E. Very large fruits and vegetables
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 1: Review
Traditional subsistence agriculture uses all of the following,
except:
a) Animal power
b) Irrigation
c) Irrigation water
d) Fossil fuels
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 2: Review
Physical weathering is characterized by:
a) The chemical interaction of water with parent
material
b) Organisms breaking down parent material
c) Wind or rain breaking down parent material
d) The dislodging or movement of soil by wind
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 3: Review
Erosion increases through all of the following, except:
a) Excessive tilling
b) Overgrazing
c) Clearing forests
d) All of the above increase erosion
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 4: Review
Which sustainable farming method involves planting rows
of trees along field edges to slow the wind?
a) Terracing
b) Crop rotation
c) Shelterbelts
d) Contour farming
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION 5: Interpreting Graphs and Data
According to this figure, which of the following is NOT true?
a) Reduced tillage
results in less nitrogen
loss
b) Conventional tillage
causes more soil loss
c) Organic carbon lost
is greater with reduced
tillage
d) Conventional and
reduced tillage have few
differences
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION: Weighing the Issues
Should developed nations fund reforestation projects in
developing nations to combat erosion and deforestation?
a) Absolutely, developing nations are facing a crisis
b) No, not with money, but developed nations could
give advice
c) No, developed nations had to solve their problems,
let the others solve their own problems
d) I don’t care, it doesn’t really affect me
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
QUESTION: Weighing the Issues
Should the U.S. government provide farmers with financial
incentives to use technologies such as no-till farming
and crop rotation?
a) Absolutely, farmers may be more likely to switch to
these techniques
b) Yes, but farmers must put any money received into
the farm
c) No, it’s not the government’s job to interfere with
farming practices
d) I don’t care, it doesn’t really affect me
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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