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AP ENVS

AP ENVS. TUESDAY NOV 26 2013. CHAPTER 9. “SOIL AND AGRICULTURE”. THE GREAT DUST BOWL P.235. “First Wave”: Plough native prairie grasses for ag development. But, grasses hold soils in place. Early 1930’s, drought, strong winds, topsoil erosion. Great Dust Bowl! Dust storms: Kansas to NY!

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AP ENVS

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  1. AP ENVS TUESDAY NOV 26 2013

  2. CHAPTER 9 “SOIL AND AGRICULTURE”

  3. THE GREAT DUST BOWLP.235 • “First Wave”: Plough native prairie grasses for ag development. • But, grasses hold soils in place. • Early 1930’s, drought, strong winds, topsoil erosion. • Great Dust Bowl! • Dust storms: Kansas to NY! • http://video.pbs.org/video/2250514396/

  4. SOIL: THE FOUNDATION FOR AGRICULTURE • AGRICULTURE • ‘The intentional human cultivation and cross-breeding of fruit, grain, and vegetable species, and the domestication of animals.’ • Modern homo sapiens: • 160,000 years: hunter-gatherers • Last 10,000 years, after last ice age: start to grow plants from seeds, domesticate animals. • 10,500 years ago, Fertile Crescent, Tigris/Euphrates, southeastern Turkey/western Iran, radiocarbon dating, wheat/barley. • 9,500 years ago, China, rice, millet, pigs.

  5. WORLD POPULATION POPULATION 185 60 10,000 YEARS BEFORE PRESENT

  6. http://www.worldometers.info/world-population/

  7. the truly great human inventions/ACHIEVEMENTS • AGRICULTURE • WRITTEN LANGUAGE • TOOL-MAKING • MEDICINES • ART • LAW • COMPUTER??

  8. not all soils are productive • Sustainable farming practices, otherwise “soil degradation”. Conversion of native grasslands to grow grains for human consumption.

  9. today: “agribusiness” THE INDUSTRIALIZATION OF FARMING

  10. SOIL AS A SYSTEMSOIL CHEMISTRY • SOIL LAB AFTER BREAK?! • What IS soil, and where do soils come from?

  11. SOIL AS A SYSTEMSOIL CHEMISTRY • SOIL LAB AFTER BREAK?! • What IS soil, and where do soils come from? • Breakdown of surface rock = minerals: • Physical weathering: wind, rain, thermal expansion/contraction • Chemical weathering: water (and acids), gases (NH3, O2) • Biological weathering: lichens • EROSION • Hundreds to thousands of years! • Decomposition of dead plant/animal matter = CARBON, N, P • “Humus”

  12. humus

  13. humus • Micropores retain soil moisture. • High oxygenation means many anionic sites for binding/chelating cations and plant nutrients. • Disease-fighting anti-oxidant activity

  14. SOIL COMPOSITION • Dr J: Collect soil chemistry parameters: • FOC: “fraction of organic carbon” • Bulk density: (dry soil bulk density) • Porosity • pH • UNIFIED SOIL CLASSIFICATION SYSTEM (USCS): • Texture • Grain size • FIGURE 9.6 (p.230)

  15. left off 11/26 SOIL COMPOSITION AND CONTAMINANT MOBILITY • SITE A: • Leaking HVOC (solvent) UST • Shallow water table • Soils: Coarse grain sands, gravels, low FOC • HIGH CONCERN! • SITE B: • Leaking fuel UST • Deeper water table • Soils: Fine-grain clays/silts, higher FOC • LOW CONCERN

  16. SOIL AS A COMPLEX, HETEROGENEOUS MEDIUM

  17. soil layers are “horizons”

  18. minerals are distributed via “leaching” Leaching is really “infiltration” Unsaturated (vadose) water table: beginning of saturated zone

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