1. Unit 6: Food
Food from Agriculture

2. Agriculture: Then and Now
Only 10% of terrestrial earth is “arable” (useable for crops)
Things to consider:
Plowing – Pushed/pulled by someone v. Machinery
Fertilization – Organics v. Synthetics
Irrigation – Water from ditches v. Sprinklers/drip systems
Pest control – By hand or machine v. Pest/herbicides

3. Back to Basics: Soil
Plants roots grow in top soil b/c of higher organic content
Most soil is formed by weathering!
Chemical rxns and subsequent temp/moisture changes
Hundreds to thousands of years to form a few centimeters
Bacteria/fungi decompose; worms aerate (with holes)

4. Today’s Soil: Bad and Good
Soil erosion – movement by wind and water; washed into rivers or blown away
We’ve lost over half of the original topsoil in the last 200 years
Loosened by poor farming practices; with no roots it washed away!
Desertification – caused by overpopulation in dry climates (Sahel region in N. Africa)
Salinization – accumulation of salts due to dry climate/poor irrigation
Soil conservation/practices
Soil retaining terraces
Contour plowing (across the slope instead of up/down)
Leaving strips of vegetation – why?
No till farming – leaving the remnants of the old crop to grow the new one
Inorganic fertilizers/compost

6. Pest Control
Around the world, insects destroy 33% of potential food harvest
Pesticides – populations can build resistance; DDT (doesn’t break down) and higher cancer rates
Biological pest control – Cane Toad!
Also bacteria (Bt kills caterpillars)
Plant defenses – VNT tomatoes
Some plants produce their own chemicals!
Growth regulators – via other mediums (dogs!)
Integrated pest management – combining these methods!
Bacillus turingiensis; Chrysanthemum
Feed the dogs a pill with a growth regulator ingested by the fleas when they bite the dog
Starts with biological methods, mechanical, and then pesticides if needed

7. Genetically Modified Organisms (GMOs)
Genetic engineering – sometimes the genes themselves are edited, sometimes we have transgenic organisms (genes from one organisms are placed in another)
Video from last class – what are your takeaways?
Sustainable agriculture – what does this mean?
Conserves natural resources
Keeps land productive
Minimizes the use of energy, water, pesticides, and fertilizers