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.
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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. • 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?
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.
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.
4) An example of a soil parent material isA. humus. B. volcanic rock. C. leaf litter. D. topsoil.
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.
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?
Causes of Soil Erosion • Wind • Water #1 • People
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.
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)
What time of year do you think most farm fields in U.S. are vulnerable to erosion?
On Ag. land in U.S. today, soil is eroding 16 times faster than it is created
Areas of serious concern Areas of some concern Stable or nonvegetative areas
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.
Evaporation Evaporation Transpiration Waterlogging Less permeable clay layer 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?