° Topic 5: Agriculture ° Lesson 1 (Agricultural Science 1) : Photosynthesis is critical: o Plants are consumed directly or indirectly # of farmers decreasing By the 1800s, traditional farming was not enough to feed the population Agricultural techniques make large production of food possible but may also be dangerous (pesticides, GMOs, etc) By 2050, population expected to grow to 10 Billion Organic: growing crops without using synthetic fertilizers & pesticides o Using manure as fertilizer, but in large scale, there is not enough manure to sustain all the crops Justus Von Liebig (1803-1873): o first chemist to look into fertilizers o Found out that Nitrogen, Phosphorus, Postassium & other smaller quantities of elements are critical in plant growth o Different plants require different ratios of elements Fritz Haber (1868-1934): o Found a way to synthetically make ammonia N 2 + 3H 2 2NH 3 o Ammonia can be directly pumped into the soil but usually is combined with nitric acid to form ammonium nitrate NH 3 + HNO 3 NH 4 NO 3 ammonium nitrate can readily produce NO 2 which contributes to greenhouse effect Alternative is hydroponic growing (soil-less growing) Alternative to pesticide is to have predatory insects °
10,000 Insect species, 8000 fungi, 2000 weeds are direct competition for the food edible by humans o Apple scab o Botrytis Fruit Rot o Stem Rust o Black spot fungus o Weeds Suck nutrients from the soil, stealing from crops ° Insects & pests Corn borer Rats Nematodes (destroy roots) Cockroaches/bed bugs that we may live with directly ° ° Control: Burning sulphur creates SO 2 , which kills insects Tobacco plant: evolved to protect itself from insects via production of nicotine Synthetic o Copper Acetoarsenate synthesized ( Paris Green) Also used as dye (in wall paint) o D.D.T WHO estimates ~25 million lives saved Physician Paul Muller won nobel prize in 1948 PROBLEM: too efficient Farmers thought benefits multiplied with amount used
Eggshells started breaking more easily DDT built up in the food chain Not biodegradable Fish consume Fish consume other fish birds consume fish Decline in eagle/osprey population BUT no clear-cut harm to humans Still banned in Canada by 1969 due to environmental hazards ( USA: 1972) However, there are cases where DDT coming back 2006: WHO suggest malaria control w/ DDT Very effective Dangerous to humans? Journal article that states rats exposed to DDT will develop fewer liver tumors than unexposed rats Exposure causes animal to generate some detoxicating enzymes that are effective on other substances as well NOT THE SAME IN HUMANS Worried about possibility of triggering disease; like cancer (b/c this substance stays around for a long time) DDT & Breast cancer correlation?
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- E number, Food additive