Lecture 20 - BIO220

Or change agriculture park grass experiment 1856 to

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Unformatted text preview: never before – Famines occurring, with much worse ones predicted • Do we change human society or change agriculture? “Park Grass Experiment,” 1856 to present 7 8 -Park Grass Experiment: fertilization regions affect genetic diversity 2 3/25/2013 -There is no recycling of nutrients happening here: -All of the resources are har vested -In a natural population, decaying plants would replenish some of t he nutrients lost in the soil when the plant extracted them to g row Soil amendments Transition from manure to industrial chemicals • Repeated crop harvests known to “exhaust” soils: crop yields decline over time (nutrients removed rather than recycled) • Lawes: dramatic growth responses to chemical fertilizers, especially grasses to nitrates/ammonia • Higher concentrations of compounds needed for optimal growth • N fertilizer from high nitrate minerals (saltpeter, KNO3 or NaNo3: Guerra del Pacífico, 1879 1883) • Haber Bosch process: natural gas + aerial nitrogen + catalyst + pressure => ammonia (fertilizer & explosives) • Nobel Prizes, historical consequences • Now 500 million tons/year, uses 3 5% of world’s natural gas supply • Adding animal dung (or whole animals) to soil known since antiquity • The main chemical benefits are NPK, which occur in higher concentrations in animals than in plant tissues… • … but other benefits come from organic matter improving soil texture and water retaining capacity. 9 10 -N2 is natural atmospheric nitrogen. It is completely i nert and useless to plants (they cannot access it) -The ability to make ammonia out of N2 allows plants to t ake it up and use it as fertilizer -In order to make N2 into NH3 (ammonia), 3% of the world's gas supply is used Made possible by Haber Bosch: food, economic collapse, war, terror, and ½ of us … Synthetic N and Human Society Atacama Desert: 170 mining towns abandoned German tank, WWI Oklahoma City 1995 11 -Although this process is the reason that we are fed and half of us a re...
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