SHORTHAND KEY: bc = because; ppl = people; pop = population; w = with; btwn = between; assoc = associated, v = very WOC Unit 2 Unit 1: Topic 5: Agriculture Lesson 1: Agricultural Science 1 Video 1 Photosynthesis : plants take up CO 2 & water then produce O 2 & glucose - in past, 70% of world was involved in farming; today about only 2% of pop supplies world’s food - in 1800’s conventional agriculture couldn’t fulfill the demand - but now with modern tech, we can produce a lot of food - but people worry about some agricultural techniques, ex. pesticides - pesticides are designed to kill, but only use a small amount of chemicals - concerned about GMO’s - by 2050, population will reach 10 billion; right now we’re having trouble feeding everyone - without fertilizers & pesticides, we can’t produce enough food - organic : growing crops without synthetic fertilizers/pesticides - relying on natural means to control insects - but not enough manure (natural fertilizer) in the world to sustain all crops - Justus Von Liebig (1873) was first to study crops - in manure, there are nutrients needed to grow crops: nitrogen , phosphorous , potassium (N,P,K) - commercial fertilizers have these 3 nutrients; different plants require a different ratio - Fritz Haber (late 19 th c) combined nitrogen & hydrogen to make ammonia synthetically - N 2 + H 2 à NH 3 - ammonia is combined w nitric acid to form ammonium nitrate (most popular fertilizer) - NH 3 + HNO 3 à NH 4 NO 3 - ammonium nitrate can be used as an explosive - but it decomposes to N 2 O (nitrous oxide/laughing gas), a greenhouse gas that prevents heat loss in atmosphere, contributing to the greenhouse effect - you don’t really need soil à soilless gardening ( hydroponics ) - grow crops in greenhouses in non-soil material (ex. ground coconut) - need the proper nutrients; Montreal has the largest hydroponic farm - can grow hydroponics in the winter; don’t need pesticides - can control insects using predatory bugs that eat insects that invade greenhouses - people sign up to get hydroponically-grown produce delivered to them Video 2 - 10,00 insect species, 8,000 fungi, 2,000 weeds - Apple Scab fungus is only a cosmetic problem, there’s nothing harmful - people just don’t want to buy apples if they look bad - farmers have to resort to agrochemicals to eliminate it - Botrytis Food Rot on strawberries - Stem Rust destroys crops - flowers affected by Black Spot Fungus - weeds sprout up between crops & suck nutrients from the soil - the Corn Borer invades corn - rats & mice burrow into grain mounds - nematodes destroy apple tree roots - cockroaches & bed bugs in homes - sulfur occurs in nature in its elemental form; it can be mined & was known to the ancients - sulfur can be burned into SO 2 which kills insects (ancient Romans were aware of this) - one of the first insecticides (but bad odour) - tobacco plant produces nicotine ( natural insecticide ) to protect itself against predators - if directly inhale it, it has harmful side effects - chemists began to learn how to combine substances à made synthetic chemicals - synthetic chemical, copper acetoarsenate ( arsenic trioxide + copper acetate ) - aka.
You've reached the end of your free preview.
Want to read all 22 pages?
- Spring '11
- pH, Pesticide, E number, Food additive