Lecture 12

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a_m_pericich
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113853
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Lecture 12
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2011-11-01 23:37:23
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Soils agriculture
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EVRN 148
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  1. Agriculture
    practice of raising crops and livestock for human use and consumption
  2. Cropland
    the land used to raise plants for human use; it produces most of our food and fiber. (76% of our food from 12% of land)
  3. Rangeland (pasture)
    the land used for grazing livestock. (16% of our food from 26% of land)
  4. Traditional Agriculture
    • Began 10,000 years ago
    • Our ancestors began intentionally planting seeds from plants whose produce was most desirable, called selective breeding.
    • People followed the same process of selective breeding with animals, creating livestock from wild species.
    • Once our ancestors learned to cultivate crops and raise animals, they began to settle in more permanent camps and villages.
    • Traditional agriculture usually relies on a variety of crops (polyculture), requires only human and animal muscle power, hand tools, and simple machines.
  5. Industrialized agriculture
    • dominates today
    • high input and high yield
    • heavy equipment
    • reliance on fossil fuels
    • commercial fertilizers and pesticides
  6. Monocultures
    • growing a single crop (often a single genetic variety) usually on a large area of land
    • improves efficiency and yield
    • Disadvantages: All the plants are susceptible to the same things. If one plant is vulnerable to a particular disease, it is likely that the rest of the plants in the field (and all your neighbors’ fields) are going to die too. Allows pest species to have higher population sizes
  7. Green revolution
    • applied technology to boost crop yields in developing nations.
    • Responsible for most (88%) of increase in food production since 1950
    • Involves shift from traditional to industrialized agriculture
    • Development and planting of monocultures high-yield crops (key crops have been rice, wheat and corn)
    • Increased yield with application of large amounts of fertilizer, pesticides, and water.
    • Grow multiple crops per year on the same piece of land
  8. Soil
    • a complex system of disintegrated rock, organic matter, water, gases, nutrients, and microorganisms
    • an ecosystem in its own right
  9. Weathering
    • 1st step in formation of soil
    • the physical, chemical, and/or biological process that converts large rock particles into smaller particles.
    • Influenced by:
    • climate - forms faster in warm, wet climates
    • organisms - plants and decomposers add organic matter over time
    • topography - hills and valleys affect exposure to sun, wind and water
    • time - can take decades to millennia
    • parent material - the base geological material in a location
  10. Bed rock
    • one type of parent material
    • the continuous mass of solid rock that makes up Earth's crust
  11. Soil profile
    the cross-section as a whole, from surface to bedrock
  12. Horizon
    • layers of soil due to the input of water and organics from the surface and minerals from weathering below
  13. O-Horizon
    mostly organic matter in various states of decay
  14. A-Horizon
    • first true layer; "topsoil"
    • most roots, decay processes, and nutrient recycling
    • food comes from this level
    • vital for Agriculture
    • varies thickness
  15. E-Horizon
    contains materials leached from upper levels, although these materials mostly accumulate in the next horizon down
  16. Leaching
    the process whereby solid particles suspended or dissolved in liquid are transported to another location. (E = lEaching)
  17. B-Horizon or subsoil
    lower organic content and higher concentration of minerals
  18. C-Horizon
    partially weathered parent rock
  19. Soil texture
    determined by size of particles; texture influences soil moisture
  20. Soil particles
    • divided into size ranges:
    • Clay: particles less than 0.002 mm in diameter
    • Silt: 0.002–0.05 mm
    • Sand: 0.05–2 mm.
    • Particle size influences infiltration rate
    • Large particles = porous – water passes through easily
    • Fine particles = smaller pore spaces – water binds to particles more tightly
    • Soil with an even mixture of the three particle sizes is known as loam – good for plant growth
  21. Soil pH
    in general, plants don't tolerate soils that are too acidic or alkaline
  22. Cation exchange
    plants gain nutrients through this process
  23. Cation exchange capacity
    expresses a soil’s ability to hold cations (preventing them from leaching and thus making them available to plants) and is a useful measure of soil fertility
  24. Land degradation
    • a general deterioration of land that diminishes its productivity and biodiversity, impairs the functioning of its ecosystems, and reduces the ecosystem services that the land offers.
    • Productive soil is a renewable resource
    • Productive soils are not evenly distributed
    • In general, temperate soils have a larger store of nutrients than tropical soils due to the speed of decomposition (warm moist=fast).
    • This influences the kind of agriculture that can be successfully practiced.
  25. Soil degradation
    soils have deteriorated in quality and declined in productivity due to drier conditions
  26. Erosion
    • the removal of material from one place and its transport toward another via wind or water
    • natural process that redistributes weathered materials
    • Common types: wind, water, splash (raindrop impact), sheet (water flowing over a gently sloping area that removes a thin uniform layer), rill (little rivulets of running water gather together and cut small channels in the soil, gully (occurs when rill erosion develops larger channels not easily dealt with by tilling)
  27. 3 Practices that increase erosion vulnerability
    • 1. Over-cultivation
    • 2. Overgrazing
    • 3. Deforestation
  28. Desertification
    • a loss of more than 10% productivity due to soil erosion, soil compaction, forest removal, overgrazing, drought, salinization, climate change, depletion of water sources, etc.
    • Can increase desert size or create new deserts.
    • Often involves positive feedback cycles, leading to a local state shift
  29. Soil Conservation
    • measures to slow soil degradation
    • Conservation districts within each county promoted soil-conservation practices
    • renamed Natural Resources Conservation Service in 1994; responsibilities expanded to include water quality protection and pollution control
  30. Crop Rotation
    • alternating the kind of crop grown in a particular field from one season or year to the next
    • returns nutrients to the soil
    • breaks cycles of disease and pests
    • growing multiple crops on one field minimizes the amount of time the field is left bare
  31. Ground cover
    • protects the soil
    • Leaving crop residue (dead vegetation) on the soil is the easiest way to provide cover
    • Cover crops can also be used (such as rye, clover, or alfalfa)
    • Can be plowed under for mulch
  32. Mulch
    • protective groundcover that protects the soil, saves water, and prevents weed growth
    • Can provide organic fertilizer as well
    • Examples: Manure, Wood chips, Straw, Seaweed, Leaves
  33. Conservation tillage
    • Controlled weeds and pests
    • Brought fresh nutrients to surface
    • Improved surface drainage
    • Aerated the soil
    • Beneficial to many crops and soil types
    • Not always the best way to grow crops → less plowing and cultivation actually better for many soils
    • Saves time, labor and fossil fuel inputs
    • Improves long term productivity and sequesters carbon
    • Reduces erosion
    • Improves soil structure and water retention
    • Main disadvantage: because root systems are left in place, additional herbicides, and fertilizers (and often additional pesticides) are required
  34. Topography Management
    reducing water runoff or wind speed, reduces erosion
  35. Contour farming
    consists of plowing furrows sideways across a hillside perpendicular to its slope and following the natural contours of the land to help precent formation of rills and gullies
  36. Terracing
    • transforms slopes into series of steps like a staircase, enabling farmers to cultivate hilly land without losing huge amounts of soil to water erosion.
    • The planting of different types of crops in alternating bands or other spatially mixed arrangements is called intercropping.
    • Provides additional ground cover
    • Simply leaving grass buffer strips in waterways can reduce runoff
    • Can reduce vulnerability to pests and replenish soil nutrient
  37. Shelterbelts
    rows of trees or other tall plants that are planted along the edges of fields to reduce wind erosion
  38. Irrigation
    • allow crops to be grown in areas that would otherwise be too arid
    • boosts agricultural productivity
    • can increase yield up to 400%
    • can create water shortage and damage soil
  39. Waterlogging
    • soils too saturated with water
    • damages both soil and roots
  40. Salinization
    • the buildup of salts in surface soil layers
  41. Inorganic fertilizers
    mined or synthetically manufactured mineral supplements
  42. Organic fertilizers
    • consist of the remains or waste of organisms
    • cause cultural eutrophication - lead to dead zones like Gulf of Mexico
  43. Precision Agriculture
    GPS used to test yields, soil, etc at specific locations and change farming based on data
  44. Overgrazing
    • when too many livestock eat too much of the plant cover
    • impedes plant regrowth and prevents replacement of biomass
    • leads to positive feedback cycles that make recovery difficult
    • soil becomes compact
  45. Rotation grazing
    • break land into little blocks and make cows graze intensely than move them
    • mimics bison grazing
    • good for the soil
  46. Agricultural Policy
    • subsidies protect against crop failure but encourage waste
    • encourage over-production of food which drives world food prices down
  47. Conservation Reserve Program
    established in the 1985 farm bill, pays farmers to stop cultivating highly erodible cropland and instead place it in conservation reserves planted with grasses and trees.
  48. Food and Agriculture Organization (FAO)
    UN promotes soil conservation and sustainable agriculture through programs led by this organization

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