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AP Environmental Soils Study Guide Review Chapter 10 (sections 1, 2 & 4) Key ideas from the reading: Case Study (page 198 - Farming the Cerrado (What are the costs and benefits?) South America the fastest growing agricultural area of the world Soils o Acidic and poor in nutrients o High in Iron o Warm humid climate Pests Rapid breakdown of organic material Benefits Costs New Varieties of soybeans Genetically modified crops Brazil is now the largest exporter Main Market -----> China BioPlastics Arc of Destruction – Encroachment on the Amazon Land Dries rapidly Increases in Drought Increasing large industrial farms Conflict between small local farms and large agriculture industry Chapter 10.1 Farming- p. 199 – What is Soil Soils are composed of mineral grains (sand, silt and clay), organic matter, organisms, water and air o Problem: Soil is renewable at an average rate of 1mm/year. Soil loss can be as high as 25mm/year on bare unprotected soil The Big Six – Soil composition o Sand and gravel o Silts and clays o Dead Organic material o Live Organic material o Water o Air. o Really, Split into three:…. 1. Particle Size 2. Organic Matter 3. Abiotic Factors Particle Size <-------> see diagram Abundant clays make soil sticky and wet. Abundant organic material and sand make the soil soft and easy to dig. AP Environmental Soils Study Guide Sandy soils drain quickly, often depriving plants of moisture. silty soils are ideal for growing crops, but they are also light and blow away easily Compacted soils have few air spaces, making soil fauna and plants grow poorly. o o Soil Texture - Texture helps determine whether rainfall drains away quickly or ponds up and drowns plants. Loam soils are usually considered best for farming because they have a mixture of clay, silt, and sand Color - reddish soils, including most tropical soils, often are colored by ironrich, rust-colored clays, which store few nutrients for plants. Deep black soils, on the other hand, are rich in organic Si San material, and thus rich in nutrients. o Organic Matter. Living: One gram of soil can contain hundreds of soil bacteria and 20 meters of tiny strands of fungal material. Dea d: The bacteria and fungi start the process See p. 201 of decomposing organic matter. Further digestion and decomposition occurs when other animals eat the bacteria and fungi. (The composition) affect soil fertility, erodibility and other factors The health of the soil ecosystem depends on environmental conditions, including: climate, topography, parent material (the mineral grains or bedrock on which soil is built), frequency of disturbance. Soils vary in texture, color and horizon development. o o o o O for organic – Decomposing leaves, fungi and bacteria A (Topsoil) – Organic matter (roots, worms etc.) and minerals E (Eluviated) - Mainly sands and very few nutrients. May not be present in all soils. B (Subsoil) – Clays that hold soluble nutrients. AP Environmental Soils Study Guide Erosion: The carrying away of materials by wind, water or ice. Wind and water erosion are the primary causes of degradation. Additional causes include: Salt accumulation from using sea water and physical deterioration, such as compaction from heavy machinery. Types: o Sheet Erosion – Water washes away a thin layer of the soil o Rill Erosion – Water creates channels in the soil o Gully Erosion – A larger version of rill erosion that cannot be removed by tilling the soil. o Wind Erosion – Usually occurs when the plant and surface litter have been removed. Practice Questions A large number of practice questions can be found online Our Text! http://glencoe.mheducation.com/sites/0021364567/student_view0/chapter10/practice_quiz.html 1 . A variety of pesticides are used and they differ from each other in A. the type of organism killed. B. the degree of toxicity. C. the degree of persistence in the environment. D. all of the above Another Environmental Science Text http://glencoe.mheducation.com/sites/0003192012/student_view0/chapter13/practice_quiz.html Mechanical weathering of soil A. occurs quickly. B. does not change the chemical nature of the rock. C. changes the chemical makeup of the parent material. D. is not important in soil production. Basic Earth Science Text –Check out the section 1 and 3 practice tests too! http://glencoe.mheducation.com/sites/0078778026/student_view0/unit2/chapter7/section_2_selfcheck_quiz-eng_.html Section 2 Self-Check Quiz-Eng. 1. A soil's composition is dependent on weathering because __________. Need a Hint? A. it makes the soil more fertile B. it contributes sediment to the soil C. it keeps the soil moist D. it moves the topsoil to other areas where it is more needed