Soil is a mixture of rocks minerals decayed material water and air Soil is one of Earths most valuable natural resources Everything that lives on the land including humans depends on soil ID: 544436
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Slide1
Soil Formation 6.E.2.3
Soil is a mixture ofrocks, minerals, decayedmaterial, water, and air.Soil is one of Earth’s most valuable natural resources. Everything that lives on the land, including humans depends on soil.Slide2
h
umus: - Material that forms when plants and animals decay.
-
dark, organic- makes space for air and water- contains minerals needed by plants- Decomposers help make humus.
loam:- rich fertile soil made of clay, sand, and silt.
Earthworms and burrowing animals such as moles mix humus and air into soil. Slide3
b
edrock (parent rock):- solid layer of rock under soil.Wherever bedrock is exposed, soil is always being formed.Why? Soil forms as rock is broken down by weathering.
Horizon:
layer of soil that is a
different color or texture.Slide4
Soil forms in
layers called horizons.O horizon: organic layer where plants grow.A horizon: topsoil: humus and
tiny rock piecesB horizon: subsoil: middle soil layer, mostly clay
C horizon: bedrock (parent rock):
partly weathered
rocksSlide5
fertility:
- measure of how well soil supports plant growth- measured from high ------ low- Soil loses its fertility when topsoil is washed away (erosion).- When soil is bare, water and wind carry soil away, plant
roots hold soil together and STOP erosion.Slide6
Dust Bowl
- during 1950’s on Great Plains of U.S.Farmers in Oklahoma plowed up grass to plant crops. Dry
weather killed the crops
which turned the bare soil to dust. Wind blew the dust creating the Dust Bowl.Slide7
Less
than ⅛ of Earth’s soil is good for farming.Soil can lose fertility if farmers continuously grow just one kind of plant in the same field year after year.crop rotation- rotating crops to a different field each year to keep soil fertile.contour
plowing
- plowing in curves on a slope to prevent soil loss.c
ontour plowingSlide8
Soil
Conservation:- using soil in ways to save it, stop erosion and keep it fertile