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Lecture 3

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Political Science

IDSB02 Development and Environment: Lecture 3 Tuesday January 24 2012 SOIL  Soils very important and now recognized, we are now relating soil science and the environment and ecology  Food security, food production, and also water contamination is central to the soils st nd  Breaking the Sod: Soil erosion, like the Mayan empire was the 1 wave, 2 wave was the plow, 3 wave was the green revolution and a push into susceptible soils like Amazon rainforests  Soil Management:  Poor soil management factors include; depletion, erosion, soil salinization and  Soil classification/knowledge  Development of soil science  Pedospheres: a bit of everything; air water and minerals, which are all main parts of the soils  Soils are highly diverse and variable, soils have many classifications/orders etc. (diverse like species)  Red soils have iron and aluminum, which are characteristics of tropical soils  Reducing conditions often grey- filled with air no water (do not need to know)  Soil profiles: typically broken down into horizons  HORIZON A: crop growth, top layer  HORIZON B: secondary layer  HORIZON C: parent material  Soil profiles can help understand how a soil will behave  How does rock turn to soils; mineral weathering of soils, could be physical weathering (wind, rain etc; sand and silt are an example of this weathering), chemical weathering (example of this type of weathering clay) or biological weathering  Dynamic natural bodies having properties from the combined effect of climate and biotic activities, as modified by topography (where you are on a hill), acting on parent material (rock) over periods of time.  These five factors are what makes up a soil  Soil texture  Sand – like tiny little rocks  Silt – in between, like bigger pieces of rock  Clay – it has gone under chemical weathering and changes the structure of the rock; it has an enormous surface area and has many inner microscopic sheets inside itself  Soil textures and properties; can help determine the behaviours and predictability of them; sand and clay examples of opposites – at a beach putting water in sand goes straight through while cups/mugs are made of clay which hold water  Table on slide 18 – know the basics  Soil Structure:  Imagine a house, the material it is built out of is soil texture- you cannot change it, but the shape of the room is the structure – it is malleable (how they are all shaped together)  4 different shapes – spheroidal, platelike, blocklike, prismlike  You would find prism like structures in dry salty (salinized
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