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

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

4. Lesson 12.1 Soil
Soil 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

5. 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

6. Soil 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.

7. Lesson 12.1 Soil
Soil Formation
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

8. Soil Formation
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

9. Soil Horizons Soil horizons are distinct layers of soil.
Lesson 12.1 Soil
Soil Horizons
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.

10. Soil Horizons Topsoil Lower Horizons
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

11. Soil Characteristics U.S. soil scientists define 12 major soil groups.
Lesson 12.1 Soil
Soil 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.
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Geyser info source - National Park Service:

12. Soil 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

13. Lesson 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.
A dust storm near Stratford, Texas, in 1935

14. Objectives
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

15. Lesson 12.2 Soil Degradation and Conservation
Erosion
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.

16. Farming Practices That Reduce Erosion
Lesson 12.2 Soil Degradation and Conservation
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

17. 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

18. Ranching Practices Ranching is the raising and grazing of livestock.
Lesson 12.2 Soil Degradation and Conservation
Ranching 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.

19. Lesson 12.2 Soil Degradation and Conservation
Forestry Practices
Forestry practices, such as clear-cutting, can increase erosion.
Today, practices that reduce soil erosion, such as selective logging, are increasingly common.

20. Desertification Loss of more than 10% of soil productivity
Lesson 12.2 Soil Degradation and Conservation
Desertification
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

21. Soil Conservation Efforts
Lesson 12.2 Soil Degradation and Conservation
Soil 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

22. Lesson 12.2 Soil Degradation and Conservation
Soil 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

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

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

25. Objectives 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

26. The Beginnings of Agriculture
Lesson 12.3 Agriculture
The Beginnings of Agriculture
People were hunter-gatherers through most of human history, until agriculture developed about 10,000 years ago when climate became warmer

27. Selective Breeding and Settlement
Lesson 12.3 Agriculture
Selective 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.

28. Traditional Agriculture
Lesson 12.3 Agriculture
Traditional Agriculture
Agriculture “powered” by people and animals
Does not require fossil fuels
Practiced widely until the Industrial Revolution

29. Industrial Agriculture
Lesson 12.3 Agriculture
Industrial 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
Did You Know? Today, more than 25% of the world’s croplands support industrial agriculture.

30. Lesson 12.3 Agriculture
The 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

31. The 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

32. Pests and Weed Control Pests: damages plants that are valuable to us
Lesson 12.3 Agriculture
Pests and Weed Control
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
Cactus moth larvae are used to control prickly pear cactus, but also threaten many rare, native cacti around the world.

33. Pest 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

34. Lesson 12.3 Agriculture
Pollinators
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.

35. Lesson 12.4 Food Production
Each year, Earth gains 75 million people and loses 5–7 million hectares of productive cropland.

36. Objectives
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

37. Food Security Arable land – land suitable for farming
Lesson 12.4 Food Production
Food 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.

38. Genetically Modified Organisms
Lesson 12.4 Food Production
Genetically 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

39. Risks and Benefits of GM Crops
Lesson 12.4 Food Production
Risks 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
Benefits:
Insect-resistant crops reduce the need for insecticides.
Herbicide-resistant crops encourage tillage conservation.

40. Industrial Food Production: Feedlots
Lesson 12.4 Food Production
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

41. Industrial Food Production: Aquaculture
Lesson 12.4 Food Production
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.

42. Effects 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

43. Sustainable Agriculture
Lesson 12.4 Food Production
Sustainable Agriculture
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.
Did You Know? Organic food purchases increased 200% from 1999 to 2008.

44. 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