Soil Formation https://youtu.be/Y1B1FtHL10k Unit 2 lesson 5 Soil Formation https://youtu.be/Y1B1FtHL10k

I. Soil= loose mixture of small rock fragments, organic matter, water & air A. What causes soil to form? Weathering of parent rock rocks break into smaller & smaller pieces takes a long time Decomposition & mixing by living things Fungi & bacteria are microorganisms that decompose (break down) the remains inside the soil humus= remains of pants and animals left behind from decomposers earthworms and moles burrow through the soil making holes and increases the amount of air that gets into the soil & improves drainage

B. Factors that determine how long it takes for soil to form Parent rock type: some rocks will weather (break apart) faster than others Climate: Soil develops more quickly in warm, wet areas Topography: soils develop better in flat areas step slopes lead to erosion Plants and animals: roots holds soil in place (lessens erosion) allowing soil to form mixing & decomposition by animals helps to form soil

C. Soil horizons soil profile: a vertical section of soil that shows all of the different layers soil horizon: the different physical properties that each soil profile has The main horizons: A Horizon= The topsoil Where decomposers live rich in humus animal burrows & plant roots darker in color

B Horizon= below A where water carries minerals less humus leeching= water carrying materials through soil has a reddish or brownish color C. Horizon= below B and least developed contains large rock fragments directly above parent rock material (rock form which soil formed from)

Stop and think Your friend tells you that it is very healthy to have a lot of worms in your garden. Why would that be? If you drew a bar graph that compared the amounts of organic matter in each horizon of soil. What could it look like?

D. Properties of soil Soil Texture= describes the relative amounts of differently sized soil particles sand- largest & makes soil feel course (0.05mm-2mm) silt- smaller than sand & makes soil feel smooth and silky (0.002-0.05) clay- smallest & very smooth or sticky when wet (>0.002mm)

Soil Color= soil color ranges from brown, black, red, orange, yellow, grey & white color indicates the types and amounts of mineral & organic matter in the soil color can indicate if the soil drains water

Soil Chemistry= is determined by the amount of minerals, sediment, and organic matter found in soil 7 = neutral above 7 (8-14) is basic below 7 (6-0) is acidic farmers will add materials to adjust the pH according to what they are growing

Pore Space= the spaces between soil particles water & air moves easily through soils with may well-connected pore spaces (well drained) best soils have ~50% pore space with ½ of it water and ½ of it air

Soil Fertility= describes how well a soil can support plant growth factors: climate, amount of humus, minerals, nutrients, & topography fertile soils have moderate rainfall, flatter land (less erosion), & are rich in humus farmers add fertilizers to increase the nutrients

Tropical soils warm, wet regions heavy rains wash away topsoil= little humus fastest soil development but not good for growing crops due to heavy leeching