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

2. What is arable land? 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. What is the history of agriculture?
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. What is the history of agriculture?
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. How does soil form?
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. What are the layers of soil?
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. What problems are associated with our use of soil?
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. What steps are taken to conserve soil?
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. What steps are taken to conserve soil?
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. What steps are taken to conserve soil?
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. You should be able to…
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.