Soil Profile and Soil Formation

Explain that soils are generally categorized by horizons based on their composition and organic material.

​I will

Describe the characteristics and formation of soil.

We will

Today

O - organic matter in various stages of decay

A - (top soil) - organic material mixed with underlaying minerals

E - leaching of metals and nutrients

B - accumulation of leeched minerals and metals

C - least weathered portion of soil profile​

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soil horizons

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Fill in the Blank

Which soil layer will have the most amount of nutrients?

O, A, E, B, or C

3 soil types: sand, silt, and clay

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-sand: 0.05 mm - 2 mm, packed​ loosely together, highly permeable, very porous (water filters within hours)

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- silt: 0.002 mm - 0.05 mm​, less permeable than sand, less porous than sand (water filters within several days)

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-​ clay: <0.002 mm, packs tightly together, way less porous and permeable (water takes years and years to filter)

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​physical properties of soil

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Open Ended

Why is it good to have a mixture of sand, silt and clay in the soil?

- determines how soil functions

- clay is the biggest mineral contributor due to its ability to attract positively charged mineral ions (cations)

- cation exchange (CEC) refers to the nutrient holding capacity of the soil (reliant on % of clay)

- more than 20% clay causes waterlogging and deprives plant roots of oxygen (dead plant)

-pH: bases (Mg, K, and Na) counteract acids (Al, & H)

- soil with high CEC and base = high productivity​

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​chemical properties of soil

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Assignment

due Monday

AP Classroom - Soil Formation & Erosion Quiz AND Soil Composition & Properties

you are highly encouraged to watch the video's before taking the quiz!

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AP Workbook - pgs 119-123

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AP Textbook - ​Read Chapter 4 Modules 9 and 10.

you are highly encouraged to complete all review questions​