Topic 5: Agriculture.docx - Lesson 1 Agricultural science 1 Photosynthesis Probably most important chemical reaction Without it there is no life

Topic 5: Agriculture.docx - Lesson 1 Agricultural science 1...

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Lesson 1: Agricultural science 1 Photosynthesis Probably most important chemical reaction Without it, there is no life Agriculture is based on photosynthesis 50 years ago about 75% of the world was involved in farming, now it’s 2% Not enough food for everyone in the world Pesticides make it possible to feed more people Organic : growing crops only by using natural techniques to get rid of insects Justus Von Liebig First scientists to study pesticides Asked: What is it in manure that allows crops to grow? Nitrogen, potassium, phosphorus Each plant requires a different ratio of the three Fritz Haber Found a way to combine nitrogen and hydrogen to make ammonia Ammonium nitrate, used in synthetic fertilizers, decomposes to make nitrous oxide (N 2 O) which is a greenhouse gas that contributes to global warming/greenhouse effect Soilless gardening Aka hydroponics Grow crops without using soil Need a good ratio of nutrients How to control insects Use predatory insects such as ladybugs Apple scab: cosmetic scab on apple that makes people not buy them even though it’s perfectly okay to eat How to control insects: Sulfur : natural, when burned creates sulfur dioxide (SO 2 ), bad to inhale Tobacco plant : natural, produces nicotine, nicotine used to prevent insects, bad to inhale Copper acetoarsenate : synthetic, “paris green” because used to rid Paris sewers of mice and rats, used in paint and wallpaper, toxic DDT : synthetic, effective against all insects, also used in WW2 to prevent lice and other insects by spraying on head, overused and caused many problems, banned in 1969 in Canada, now used to control malaria Paul Miller : Nobel prize for creating DDT Rachel Carson: book “silent spring”, pesticides should be used carefully, used DDT as an example in the environment Malathion : can be used to wipe out mosquitoes but toxic in high doses Some pesticide risks are real, but some are also imagined Rotenone : naturally extracted from the roots of the darus plant , linked to Parkinson’s disease Subtle chronic effects: more concerning, long effects of pesticides Some pesticides can disrupt hormones
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