12 Soil and Agriculture CHAPTER. Lesson 12.1 Soil About 38% of Earth’s land surface is used for...

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Lesson 12.1 SoilLesson 12.1 Soil

About 38% of Earth’s land surface is used for agriculture.About 38% of Earth’s land surface is used for agriculture.

ObjectivesObjectives

• Explain 3 processes by which soil forms•Describe the horizons that make up a soil profile• List the four characteristics used to classify soil

• Explain 3 processes by which soil forms•Describe the horizons that make up a soil profile• List the four characteristics used to classify soil

Soil CompositionSoil Composition

• Soil is made up of disintegrated rock, remains and waste of organisms, water, gases, nutrients, and microorganisms.

• Renewable resource

• If depleted of nutrients, it takes a very long time (generations) to reform

Lesson 12.1 Soil

Factors That Influence Soil Formation

Factors That Influence Soil Formation

• Climate• Forms faster in warm climates with high precipiation

• Organisms• Worms and burrowing animals aerate and mix soil speeding up

decomposition• Plants add organic matter

• Landforms• Affect soils exposure to sun, wind and water• Steep slopes increase runoff and erosion

• Parent material• The chemical and physical makeup of whatever substance the soil

comes from affects its formation

• Time• Soil takes many years (even millennia in some cases) to form

• Climate• Forms faster in warm climates with high precipiation

• Organisms• Worms and burrowing animals aerate and mix soil speeding up

decomposition• Plants add organic matter

• Landforms• Affect soils exposure to sun, wind and water• Steep slopes increase runoff and erosion

• Parent material• The chemical and physical makeup of whatever substance the soil

comes from affects its formation

• Time• Soil takes many years (even millennia in some cases) to form

Soil FormationSoil Formation

• 45% mineral matter, 5% organic matter, 50% air/water

•Occurs during primary succession

• Parent material is the base geological material in a particular location• Ex: lava, volcanic ash, rock, sand, bedrock, etc.

• Bedrock is the continuous mass of solid rock that makes up Earth’s crust.

• 45% mineral matter, 5% organic matter, 50% air/water

•Occurs during primary succession

• Parent material is the base geological material in a particular location• Ex: lava, volcanic ash, rock, sand, bedrock, etc.

• Bedrock is the continuous mass of solid rock that makes up Earth’s crust.


• Weathering: Physical and chemical breaking of rocks and minerals into smaller pieces

• Physical – result of anything touching a rock such as wind and rain and changes in temperature

• Chemical – when water or other substances break down parent material transforming it into a new material

• Weathering: Physical and chemical breaking of rocks and minerals into smaller pieces

• Physical – result of anything touching a rock such as wind and rain and changes in temperature

• Chemical – when water or other substances break down parent material transforming it into a new material

Lesson 12.1 Soil


• Erosion and deposition: Pick-up, transport, and drop-off of material from one place to another• Erosion and deposition: Pick-up, transport, and

drop-off of material from one place to another

•Decomposition: Breakdown of waste, organisms, and organic material into simple molecules• Ex: when leaves fall off trees and are broken down by

decomposers and detritivores• Humus – dark, spongy, crumbly mass of material made up

of complex organic compounds

•Decomposition: Breakdown of waste, organisms, and organic material into simple molecules• Ex: when leaves fall off trees and are broken down by

decomposers and detritivores• Humus – dark, spongy, crumbly mass of material made up

of complex organic compounds

Soil HorizonsSoil Horizons

• Soil horizons are distinct layers of soil.

• A cross-section of soil horizons is a soil profile.

• Soil horizons are distinct layers of soil.

• A cross-section of soil horizons is a soil profile.

Did You Know? In general, organic matter is concentrated in the O and A horizons, making them the most critical for agriculture.

Did You Know? In general, organic matter is concentrated in the O and A horizons, making them the most critical for agriculture.

Lesson 12.1 Soil

Soil HorizonsSoil Horizons

• Topsoil• Has the most plant nutrients available• Home to most of the organisms that live in soil• Fragile

• Lower Horizons• As you move downward through soil, particle size increases

and organic matter decreases• Leaching transports minerals downward

• Think of coffee grounds in a filter to understand how leaching works• Leaching may carry substances into ground water which could

pose a threat to human health

• Topsoil• Has the most plant nutrients available• Home to most of the organisms that live in soil• Fragile

• Lower Horizons• As you move downward through soil, particle size increases

and organic matter decreases• Leaching transports minerals downward

• Think of coffee grounds in a filter to understand how leaching works• Leaching may carry substances into ground water which could

pose a threat to human health

Soil CharacteristicsSoil Characteristics

•U.S. soil scientists define 12 major soil groups.

• Soil groups are further classified according to properties such as color, structure, pH, and texture.

• Soil texture is based on particle size.

•U.S. soil scientists define 12 major soil groups.

• Soil groups are further classified according to properties such as color, structure, pH, and texture.

• Soil texture is based on particle size.

Lesson 12.1 Soil

Soil CharacteristicsSoil Characteristics

•Color – reveals details about its composition and fertility• dark soil = rich in nutrients, pale soil = nutrient poor

• Texture – influences soils workability, indicates how porous soil is• Loam – soil with a relatively even mixture of sand, clay and

silt

• Structure – arrangement of soil particles• “clumpiness”

• pH – how acidic/alkaline soil is• Affects ability to support plant growth• Affected by acid rain and leaching

•Color – reveals details about its composition and fertility• dark soil = rich in nutrients, pale soil = nutrient poor

• Texture – influences soils workability, indicates how porous soil is• Loam – soil with a relatively even mixture of sand, clay and

silt

• Structure – arrangement of soil particles• “clumpiness”

• pH – how acidic/alkaline soil is• Affects ability to support plant growth• Affected by acid rain and leaching

Lesson 12.2 Soil Degradation and ConservationLesson 12.2 Soil Degradation and Conservation

Some estimates predict that 50 million people could be displaced in the next 10 years due to desertification, a form of soil degradation.

Some estimates predict that 50 million people could be displaced in the next 10 years due to desertification, a form of soil degradation.

A dust storm near Stratford, Texas, in 1935


•Describe some practices that can lead to soil erosion and some that can preserve it•Describe the causes and effects of desertification•Discuss the activities of U.S. and International

agricultural organizations• Explain how irrigation and pesticide use can cause soil

pollution

•Describe some practices that can lead to soil erosion and some that can preserve it•Describe the causes and effects of desertification•Discuss the activities of U.S. and International

agricultural organizations• Explain how irrigation and pesticide use can cause soil

pollution

ErosionErosion

Lesson 12.2 Soil Degradation and Conservation

• The process by which material, such as topsoil, is moved from one place to another

• Caused by natural processes and human activities

• Often occurs faster than soil is formed, depleting fertile topsoil

• Crops, trees, and other plant communities protect soil from erosion.

Did You Know? More than 19 billion hectares (47 billion acres) of the world’s croplands suffer from erosion and other forms of soil degradation resulting from human activities.

Did You Know? More than 19 billion hectares (47 billion acres) of the world’s croplands suffer from erosion and other forms of soil degradation resulting from human activities.

Farming Practices That Reduce Erosion

Farming Practices That Reduce Erosion

• Intercropping: Different crops mixed together• Helps slow erosion

• Reduces plant vulnerability to insects and disease

•Crop rotation: Crops are alternated. • Can return nutrients to the soil

• Breaks disease and pest cycles

• Cover crops – farmers plant crops to reduce erosion after a field has been harvested and before the next season’s planting

• Intercropping: Different crops mixed together• Helps slow erosion

• Reduces plant vulnerability to insects and disease

•Crop rotation: Crops are alternated. • Can return nutrients to the soil

• Breaks disease and pest cycles

• Cover crops – farmers plant crops to reduce erosion after a field has been harvested and before the next season’s planting


Farming Practices that Reduce Erosion

Farming Practices that Reduce Erosion

• Shelterbelts: Tall plants block wind.

•Conservation tillage: Soil turnover is reduced.• Require high amounts of weed-killer and fertilizer

• Improve soil quality and reduce erosion

• Terracing: Steep slopes turned into “steps”• Only sustainable way to farm mountains

•Contour farming: Planting perpendicular to hill’s slope• Reduces soil erosion

• Crops act as a dam that catches soil before it is washed away

• Shelterbelts: Tall plants block wind.

•Conservation tillage: Soil turnover is reduced.• Require high amounts of weed-killer and fertilizer

• Improve soil quality and reduce erosion

• Terracing: Steep slopes turned into “steps”• Only sustainable way to farm mountains

•Contour farming: Planting perpendicular to hill’s slope• Reduces soil erosion

• Crops act as a dam that catches soil before it is washed away

Ranching PracticesRanching Practices•Ranching is the

raising and grazing of livestock.

•Overgrazing occurs when animals eat the grasses faster than they can grow back

•Range managers encourage grazing limits and enforce them on publicly owned land.

•Ranching is the raising and grazing of livestock.

•Overgrazing occurs when animals eat the grasses faster than they can grow back

•Range managers encourage grazing limits and enforce them on publicly owned land.


Forestry PracticesForestry Practices


• Forestry practices, such as clear-cutting, can increase erosion.

• Today, practices that reduce soil erosion, such as selective logging, are increasingly common.

• Forestry practices, such as clear-cutting, can increase erosion.

• Today, practices that reduce soil erosion, such as selective logging, are increasingly common.

DesertificationDesertification


• Loss of more than 10% of soil productivity

• Causes: soil compaction, erosion, overgrazing, drought, or other factors

• Arid and semi-arid lands are most prone.

• Affects large amounts of Earth’s land areas—up to one third, according to one estimate

• The Dust Bowl was a major desertification event in the 1930s.

• Loss of more than 10% of soil productivity

• Causes: soil compaction, erosion, overgrazing, drought, or other factors

• Arid and semi-arid lands are most prone.

• Affects large amounts of Earth’s land areas—up to one third, according to one estimate

• The Dust Bowl was a major desertification event in the 1930s.

Area affected by the Dust Bowl

Soil Conservation EffortsSoil Conservation Efforts


•U.S. Soil Conservation Act (1935): Established the Soil Conservation Service, today called the Natural Resources Conservation Service

• Farmer-Centered Agricultural Resource Management Program (FARM): A United Nations effort that focuses on resource challenges in developing nations

•U.S. Soil Conservation Act (1935): Established the Soil Conservation Service, today called the Natural Resources Conservation Service

• Farmer-Centered Agricultural Resource Management Program (FARM): A United Nations effort that focuses on resource challenges in developing nations

Soil PollutionSoil Pollution


• Irrigation – the providing of water other than precipitation to crops

• Pesticides – chemicals that kill organisms that attack or compete with plants we value

• Toxic pesticides can remain in soil for a long time, eventually filtering to groundwater and evaporate into the air

• Irrigation – the providing of water other than precipitation to crops

• Pesticides – chemicals that kill organisms that attack or compete with plants we value

• Toxic pesticides can remain in soil for a long time, eventually filtering to groundwater and evaporate into the air

Soil PollutionSoil Pollution

• Too much, or carelessly timed irrigation can waterlog crops and lead to salinization—a buildup of salts in upper soil horizons.• In dry areas, evaporating water from topsoil pulls water up

from lower horizons, carrying dissolved salts• Irrigation water also contains dissolved salts

• Salinization is prevented by • not planting crops that need a lot of water in dry areas• Irrigating with water with low dissolved salts• During irrigation, provide no more water than the crops need

as close to the roots as possible

• Too much, or carelessly timed irrigation can waterlog crops and lead to salinization—a buildup of salts in upper soil horizons.• In dry areas, evaporating water from topsoil pulls water up

from lower horizons, carrying dissolved salts• Irrigation water also contains dissolved salts

• Salinization is prevented by • not planting crops that need a lot of water in dry areas• Irrigating with water with low dissolved salts• During irrigation, provide no more water than the crops need

as close to the roots as possibleDid You Know? Salinization costs farmers $11 billion in crop income a year worldwide.

Did You Know? Salinization costs farmers $11 billion in crop income a year worldwide.

Lesson 12.3 AgricultureLesson 12.3 Agriculture

Humans have been practicing agriculture for about 10,000 years.Humans have been practicing agriculture for about 10,000 years.


•Discuss the beginnings of agriculture• Explain the importance of industrial agriculture and the

green revolution• Identify different types of pest control• Explain the importance of pollinators to agriculture

•Discuss the beginnings of agriculture• Explain the importance of industrial agriculture and the

green revolution• Identify different types of pest control• Explain the importance of pollinators to agriculture

The Beginnings of AgricultureThe Beginnings of Agriculture• People were hunter-gatherers through most of human history, until

agriculture developed about 10,000 years ago when climate became warmer• People were hunter-gatherers through most of human history, until

agriculture developed about 10,000 years ago when climate became warmer

Lesson 12.3 Agriculture

Selective Breeding and SettlementSelective Breeding and Settlement

• In early agriculture, people began planting seeds from plants they liked most, a form of selective breeding.

• Crop cultivation enabled people to settle permanently, often near water sources, and raise livestock.

• Agriculture and livestock provided a stable food supply, which allowed the development of modern civilization.

• In early agriculture, people began planting seeds from plants they liked most, a form of selective breeding.

• Crop cultivation enabled people to settle permanently, often near water sources, and raise livestock.

• Agriculture and livestock provided a stable food supply, which allowed the development of modern civilization.


Traditional AgricultureTraditional Agriculture

• Agriculture “powered” by people and animals

•Does not require fossil fuels

• Practiced widely until the Industrial Revolution

• Agriculture “powered” by people and animals

•Does not require fossil fuels

• Practiced widely until the Industrial Revolution


Industrial AgricultureIndustrial Agriculture

• Agriculture that requires the use of fossil fuels

• Involves mechanized farming technology, manufactured chemicals pesticides, synthetic fertilizers and large-scale irrigation

• To be efficient, large areas are planted with a single crop in a monoculture.

• Monocultures reduce biodiversity and risk catastrophic crop fail

• Agriculture that requires the use of fossil fuels

• Involves mechanized farming technology, manufactured chemicals pesticides, synthetic fertilizers and large-scale irrigation

• To be efficient, large areas are planted with a single crop in a monoculture.

• Monocultures reduce biodiversity and risk catastrophic crop fail


Did You Know? Today, more than 25% of the world’s croplands support industrial agriculture.

Did You Know? Today, more than 25% of the world’s croplands support industrial agriculture.

The Green RevolutionThe Green Revolution• Introduced new technology, crop

varieties, and farming practices to the developing world in the mid- to late 1900s

• “Green” refers to covered in plants, not environmentally friendly

Benefits:• Increased crop yields and saved millions of

people from starvation in India and Pakistan because developed nations shared their farming technology with developing nations such as new crop strains, pesticides, fertilizers, irrigation, etc.

• Prevented some deforestation and habitat loss by increasing yields on cultivated land

• Introduced new technology, crop varieties, and farming practices to the developing world in the mid- to late 1900s

• “Green” refers to covered in plants, not environmentally friendly

Benefits:• Increased crop yields and saved millions of

people from starvation in India and Pakistan because developed nations shared their farming technology with developing nations such as new crop strains, pesticides, fertilizers, irrigation, etc.

• Prevented some deforestation and habitat loss by increasing yields on cultivated land


The Green RevolutionThe Green Revolution

Costs:• Led to a 7000% increase in energy used by agriculture

• Worsened erosion, salinization, desertification, eutrophication, and pollution

• Use of fossil fuel powered machinery increased air pollution and contributed to global warming

Costs:• Led to a 7000% increase in energy used by agriculture

• Worsened erosion, salinization, desertification, eutrophication, and pollution

• Use of fossil fuel powered machinery increased air pollution and contributed to global warming

• Pests: damages plants that are valuable to us

• Weeds: competes with our plants

• Chemical pesticides: Effective and cheap, but can lead to resistance

• Integrated pest management: Increasingly popular solution, combines chemical and biological pest-control methods

• Pests: damages plants that are valuable to us

• Weeds: competes with our plants

• Chemical pesticides: Effective and cheap, but can lead to resistance

• Integrated pest management: Increasingly popular solution, combines chemical and biological pest-control methods

Pests and Weed ControlPests and Weed Control


Cactus moth larvae are used to control prickly pear cactus, but also threaten many rare, native cacti around the world.

Pest and Weed ControlPest and Weed Control

•Biological pest control: purposeful introduction of organisms that eat pests/weeds to environment• Bt – naturally occurring soil bacterium, produces protein

that kills caterpillars and fly/beetle larvae• Benefits: permanent, requires no maintenance,

environmentally harmless• Costs: introduced organisms may become invasive,

may harm nontargeted organisms

•Biological pest control: purposeful introduction of organisms that eat pests/weeds to environment• Bt – naturally occurring soil bacterium, produces protein

that kills caterpillars and fly/beetle larvae• Benefits: permanent, requires no maintenance,

environmentally harmless• Costs: introduced organisms may become invasive,

may harm nontargeted organisms

PollinatorsPollinators• Pollination is the process by

which plants reproduce sexually.

• Agriculture relies on pollinators, such as insects.

•Native and domesticated pollinator populations have declined due to pesticide use, parasites, and other as-of-yet unknown causes.

• Pollination is the process by which plants reproduce sexually.

• Agriculture relies on pollinators, such as insects.

•Native and domesticated pollinator populations have declined due to pesticide use, parasites, and other as-of-yet unknown causes.


Did You Know? Bees and other insects pollinate 800 species of cultivated plants.

Did You Know? Bees and other insects pollinate 800 species of cultivated plants.

Lesson 12.4 Food ProductionLesson 12.4 Food Production

Each year, Earth gains 75 million people and loses 5–7 million hectares of productive cropland.

Each year, Earth gains 75 million people and loses 5–7 million hectares of productive cropland.


• Explain why the world needs to grow more food and to grow it sustainably•Discuss genetically modified food•Describe the advantages and disadvantages of

industrial food production•Discuss sustainable agriculture

• Explain why the world needs to grow more food and to grow it sustainably•Discuss genetically modified food•Describe the advantages and disadvantages of

industrial food production•Discuss sustainable agriculture

Food SecurityFood Security

• Arable land – land suitable for farming

• Since 1960, our ability to produce food has grown faster than the human population

• but 1 billion people are hungry worldwide

• may not always be the case in the future though

•Malnutrition and undernourishment are most common in the developing world.

• Malnutrition – a shortage of nutrients that the body needs

• Agriculture scientists and policymakers are working toward food security—the guarantee of an adequate food supply for all people at all times.

• Arable land – land suitable for farming

• Since 1960, our ability to produce food has grown faster than the human population

• but 1 billion people are hungry worldwide

• may not always be the case in the future though

•Malnutrition and undernourishment are most common in the developing world.

• Malnutrition – a shortage of nutrients that the body needs

• Agriculture scientists and policymakers are working toward food security—the guarantee of an adequate food supply for all people at all times.

Lesson 12.4 Food Production

Genetically Modified OrganismsGenetically Modified Organisms

•Genetically Modified Organisms (GM) - Organisms that have had their DNA modified

•Genetic Engineering – any process in which scientists directly manipulate an organism’s DNA

• Commonly engineered traits include rapid growth, pest resistance, and frost tolerance.

• In the United States, 85% of corn and 90% of soybean, cotton, and canola crops come from GM strains.

• Biotechnology – the use of genetic engineering to introduce new genes into organisms to produce more valuable products

•Genetically Modified Organisms (GM) - Organisms that have had their DNA modified

•Genetic Engineering – any process in which scientists directly manipulate an organism’s DNA

• Commonly engineered traits include rapid growth, pest resistance, and frost tolerance.

• In the United States, 85% of corn and 90% of soybean, cotton, and canola crops come from GM strains.

• Biotechnology – the use of genetic engineering to introduce new genes into organisms to produce more valuable products


Risks and Benefits of GM CropsRisks and Benefits of GM Crops

•Risks:• Potential for “superpests” that are resistant to pest-resistant crops

• Contamination of non-GM plants• Foods may be dangerous for people to eat

•Risks:• Potential for “superpests” that are resistant to pest-resistant crops

• Contamination of non-GM plants• Foods may be dangerous for people to eat


• Benefits:• Insect-resistant crops

reduce the need for insecticides.

• Herbicide-resistant crops encourage tillage conservation.

Industrial Food Production: Feedlots

Industrial Food Production: Feedlots

• Alternative to open grazing in which energy-rich food is delivered to a concentrated group of livestock or poultry

•Benefits: Reduces soil degradation and fertilizer use

•Costs: Requires antibiotic use; potential for water contamination and animal stress; steroid use in cattle; overcrowding stresses animals

• Alternative to open grazing in which energy-rich food is delivered to a concentrated group of livestock or poultry

•Benefits: Reduces soil degradation and fertilizer use

•Costs: Requires antibiotic use; potential for water contamination and animal stress; steroid use in cattle; overcrowding stresses animals


Industrial Food Production: Aquaculture

Industrial Food Production: Aquaculture

• Fish farming in a controlled environment• Benefits: Can be sustainable; reduces

by-catch; reduces fossil fuel use• Costs: More difficult to control spread

of diseases; produces a lot of waste; potential for farm-raised animals to escape into wild


Did You Know? Aquaculture is the fastest-growing type of food production.

Did You Know? Aquaculture is the fastest-growing type of food production.

Effects of Plant DiversityEffects of Plant Diversity

•GM plants may pollinate wild strains of plants, outcompete them and force them into extinction• If all species of a plant are genetically the same, one

pest can wipe out an entire plant species•We have already lost genetic diversity in our crop

plants• Market forces discourage diversity • Seed banks – organizations that preserve seeds of diverse

plants as a kind of insurance policy against global crop collapse

•GM plants may pollinate wild strains of plants, outcompete them and force them into extinction• If all species of a plant are genetically the same, one

pest can wipe out an entire plant species•We have already lost genetic diversity in our crop

plants• Market forces discourage diversity • Seed banks – organizations that preserve seeds of diverse

plants as a kind of insurance policy against global crop collapse

Sustainable AgricultureSustainable Agriculture

Did You Know? Organic food purchases increased 200% from 1999 to 2008.

Did You Know? Organic food purchases increased 200% from 1999 to 2008.

•Does not deplete soil faster than it forms•Does not reduce the amount or

quality of soil, water, and genetic diversity essential to long-term crop and livestock production•Organic agriculture is sustainable

agriculture that does not use synthetic chemicals.• Local, small-scale agriculture reduces

the use of fossil fuels and chemicals used for transportation and storage.

•Does not deplete soil faster than it forms•Does not reduce the amount or

quality of soil, water, and genetic diversity essential to long-term crop and livestock production•Organic agriculture is sustainable

agriculture that does not use synthetic chemicals.• Local, small-scale agriculture reduces

the use of fossil fuels and chemicals used for transportation and storage.


What It Means to be “Organic”What It Means to be “Organic”

•Crops• Can’t be genetically engineered, treated with radiation,

produced in synthetic fertilizer• No use of sewage sludge• Use of pesticide is prohibited

• Livestock• Must be fed 100% organic feed• Use of hormones and antibiotics is prohibited• Animals must have access to outdoors

•Crops• Can’t be genetically engineered, treated with radiation,

produced in synthetic fertilizer• No use of sewage sludge• Use of pesticide is prohibited

• Livestock• Must be fed 100% organic feed• Use of hormones and antibiotics is prohibited• Animals must have access to outdoors

12 Soil and Agriculture CHAPTER. Lesson 12.1 Soil About 38% of Earth’s land surface is used for...

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