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Chapter 15, Section 2: Crops & Soil Standards: SEV4a, b, c.

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Presentation on theme: "Chapter 15, Section 2: Crops & Soil Standards: SEV4a, b, c."— Presentation transcript:

1 Chapter 15, Section 2: Crops & Soil Standards: SEV4a, b, c

2  Land that can be used to grow crops  Only 10% of land on earth is arable.  Urban areas occupy 3% and are currently invading arable land.

3  Traditional Agriculture  Plows pulled by animals to turn & loosen soil.  Organic fertilizer (animal manure) used to enrich soil for plant growth.  Drainage ditches were dug to bring water to plants for irrigation.  Weeds pulled by hand.

4  Modern Agriculture  Large machines plow land and harvest crops.  Synthetic chemical fertilizers used instead of manure  Overhead sprinklers & drip systems irrigate crops  Synthetic chemical pesticides are used to kill pests  The chemical fertilizer & pesticides are often oil based.

5  Rock breaks down into fine particles and mix with decomposing matter to make topsoil.  Chemical Weathering  Rock is broken down by chemical rxn btwn water & a substance in rock that can be dissolved ▪ EX: Lichen secrete acids that break rock down  Physical Weathering  Water  Wind  Bacteria, fungi, earthworms all break down dead matter & recycle nutrients back to soil.  Earthworm burrows allow air to circulate in soil

6  Surface litter/Organic layer- leaf litter, partially decomposed organic matter  Topsoil- organic matter, living organisms, fine rock particles; also water & air  Subsoil- larger rock particles, some organic matter, mostly inorganic compounds  Parent Rock- bedrock that has been weathered  Bedrock- solid rock layer

7  Erosion  Movement of rock & soil by wind or water  ½ of topsoil in US has eroded- affects ability to grow crops  Farming increases rate of erosion through plowing & irrigation  Desertification  Land in arid/semi-arid areas becomes more desert-like  Due to overgrazing & planting too many crops  Salinization  Soil too salty to grow plants in.  Becomes salty from ▪ Over-irrigation ▪ Low rainfall  Flooding field with freshwater can remove excess salt White salt deposits on cropland

8  Terracing- cutting levels into steep hillside to slow water erosion  Contour plowing- plowing across hill on gentle slope to slow water erosion  Strip plowing- leaving strips of vegetation in every other row so roots hold soil in place

9  Drip irrigation- using series of hoses to drip water around plant roots; expensive but very effective  No-till harvesting- harvesting crop without turning soil. Roots hold soil to prevent erosion  Cons- old crop might crowd out new crop and decrease crop yields

10  Crop Rotation-  Rotating crops to replenish nutrients in soil. ▪ Corn crops remove nutrients from soil so planting a crop of soybean the next year will replenish those nutrients back to the soil.  Compost  Partly decomposed organic matter from yard waste, home food waste, or crop waste  Added with chemical fertilizers to enrich soil.

11  Explain the difference between traditional and modern farming methods.  Describe the structure and composition of fertile soil.  Explain why the presence of plants helps prevent soil erosion.  Explain why soil conservation is an important agricultural practice.


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