chapter 12 soil and agriculture
DESCRIPTION
Chapter 12 Soil and Agriculture. Mr. Manskopf Class Web Site Http://www.manskopf.com. Essential Questions Covered. What are the components of the soil? How is soil formed? What are some of the effects of soil erosion on the land? Describe the impact of human activities on the land. - PowerPoint PPT PresentationTRANSCRIPT
Essential Questions Covered• What are the components of the soil?• How is soil formed?• What are some of the effects of soil erosion on the
land?• Describe the impact of human activities on the
land.• How do recycling and composting programs affect
the soil?• What impact do pesticides have on the soil?• What affect do fertilizers have on the nitrogen
cycle?
About 38% of Earth’s land surface is used for agriculture.
About 38% of Earth’s land surface is used for agriculture.
Section 1 Soil• Explain how soil is formed.• Describe the different layers
(horizons) of soil.• List four characteristics used to
classify soil.
What is soil made of?• Soil is made up of
minerals, organic matter, air, and water.
• Soil composition is influenced by climate, organisms, landforms, parent material, and time
Soil Composition • Soil is a thin layer
over most land that is a complex mix of rock, nutrients, decaying matter, water, air and billions of organisms…many microscopic decomposers
Why is soil important• Renewable
resource…SLOW• Depends upon
climate (1cm in 15yrs.)
• Basis of life• Filters water• Water storage• Habitat
Soil Formation•Weathering: Physical and
chemical breaking of rocks and minerals into smaller pieces
•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
Soil Horizons• Soil horizons are
distinct layers of soil.
• A cross-section of soil horizons is a soil profile.
• “A” Most Critical
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.
Soil Characteristics • Soil groups are
further classified according to properties such as color, structure, pH, and texture.• Soil texture is based
on particle size.
Topsoil Color a Great Quick Indicator
Dark, loamy, neutral pH are some of best soils for farming
Dark color often means lots of decayed material (nutrients)
Section 1 Review
• Explain how soil is formed.• Describe the different layers
(horizons) of soil.• List four characteristics used to
classify soil.
Section 1 Quiz
1) After a catastrophe, soil formation is the first step in•A. primary succession. •B. secondary succession. •C. a climax community.
2) Most of the nutrients in soil come fromA. chemical weathering. B. mechanical weathering. C. erosion. D. decomposition.
3) A farmer interested in raising healthy crops should look for aA. heavy clay soil with a high pH and a dark color. B. loamy soil with a low pH and a light color.C. loamy, clumpy soil with a neutral pH and a dark color. D. sandy soil with a high pH, no clumps, and a light color.
5) As a farmer, you would be most concerned with the quality of the soil in theA. O horizon. B. A horizon. C. E horizon. D. R horizon.
6) A rancher interested in the quality of the soil in her pasture might use which aspect of soil as a quick indicator of the pasture’s overall fertility?A. color B. smell C. structure D. pH E. Taste
7) Short Answer: If you were to travel to the desert in Arizona, you might find Horizon Layer O and A missing. Why?
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.
Section 2 Soil Degradation and Conservation
• What causes soil erosion?• How serious of a problem is it?• What are ways that farmers,
ranchers and forestry lead to soil erosion?
Soil Erosion
• 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.
Impacts of Soil Erosion• Loss of soil fertility• Sediment runoff causes
problems in surface water (pollution, clog ditches, boat channels, reservoirs)
• #1 source of U.S. water pollution
• Renewable only on LONG timeframes (200-1,000yrs. for 1 inch)
Farming Practices That Reduce Erosion
• Intercropping: Different crops mixed together
• Crop rotation: Crops are alternated.
• Shelterbelts: Tall plants block wind.
• Conservation tillage: Soil turnover is reduced.
• Terracing: Steep slopes turned into “steps”
Ranching Practices• Ranching is the raising and
grazing of livestock.
• Overgrazing causes and worsens many soil problems.
• Range managers encourage grazing limits and enforce them on publicly owned land.
Forestry Practices• Forestry practices,
such as clear-cutting, can increase erosion.
• Today, practices that reduce soil erosion, such as selective logging, are increasingly common.
Soil Pollution• Too much, or carelessly
timed irrigation can waterlog crops and lead to salinization—a buildup of salts in upper soil horizons.
• Toxic pesticides can remain in soil for a long time, eventually filtering to groundwater.
Section 2 Review
• What causes soil erosion?• How serious of a problem is it?• What are ways that farmers,
ranchers and forestry lead to soil erosion?
Humans have been practicing agriculture for about 10,000 years.
Humans have been practicing agriculture for about 10,000 years.
Aldo Leopold
There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery store, and the other that heat from the furnace.
Section 3 Agriculture
• Describe the history of farming.• Analyze the costs and benefits of the “Green
Revolution”• What are some ways farmers control weeds
and pests?• Why are pollinators important to farmers?
The Beginnings of Agriculture
People were hunter-gatherers through most of human history, until agriculture developed about 10,000 years ago.
Agriculture History• In early agriculture,
people began planting seeds from plants they liked most
• Agriculture and livestock provided a stable food supply, which allowed the development of modern civilization.
The Green Revolution• Introduced new technology, crop
varieties, and farming practices to the developing world in the mid- to late 1900s
Benefits:
• Increased crop yields and saved millions of people from starvation in India and Pakistan
• Prevented some deforestation and habitat loss by increasing yields on cultivated land
Green RevolutionCosts:• Led to a 7000% increase in energy used by
agriculture
• Worsened erosion, salinization, desertification, eutrophication, and pollution
Pests and Weed Control (Farmers Enemies)
• Chemical pesticides: Effective and cheap, but can lead to resistance
•Biological pest control: Permanent solution, but can harm nontarget organisms
•Integrated pest management: Increasingly popular solution, combines chemical and biological pest-control methods
Pests and Weed Control
Cactus moth larvae are used to control prickly pear cactus, but also threaten many rare, native cacti around the world.
Pollinators• 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