Unit 6: Food Food from Agriculture

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

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)

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

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

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