Download Soil

 Defined as the part of dirt that will support life
 Found in all places all over the world, but not all soil is
the same
 Oceans and deserts have sandy soil, swamps are muddy soil
 Soil is divided into four parts
 Water  Found in pore spaces and supplies the moisture and
nutrients for root systems
 Air  Found in pore spaces and is a source of carbon dioxide
and oxygen for plants and animals
 Mineral Matter All the sediments that make up most of the
soil
 Organic Matter  Humus is the decayed matter from dead
animals and plants that supplies nutrients to soils
 Soil is made from the weathering and erosion of rocks
 Five factors that determine the soil types
 1. Climate (most important factor)
 Warmer and wetter climates that encourage all types of
weathering will have some of the thickest soils
 Drier, cooler climates will have thinner, not good soils
 2. Parent Material
 The sediments in the soil have to come from an original rock
that got weathered called a parent rock
 The harder the parent rock, the less sediments you have in
the soil because not many rocks will weather easily
 3. Time
 The longer the time you have to weather the rocks, the
thicker the soil that you will have.
 4. Organisms
 Plants are the mains source of organic humus in the soils
 Microorganisms and fungi will decompose the dead stuff into
nutrients that animals and plants can use
 5. Slope
 On steeper slopes, erosion will increase, very little water gets
into the soil, and the soil itself is very thin because much of it
will be pulled down by gravity
 Flatter areas will have erosion decrease, lots of water in the
soil, and the soil is generally thicker
 Soil is not the same all the way down to the crust, it
changes as you go further down
 The layers of soil are called the soil profile
 There are four layers to the soil profile
 A-Horizon, B-Horizon, C-Horizon, and the
Unweathered Parent Material (UPM) also known as the
crust of the Earth
 This extremely thin
layer is the pure
organic layer of the
soil profile
 This layer is made of
humus, the dead
leaves and organic
bodies of the
organisms that live
there
 Top layer of the soil that
contains most of the
nutrients for the plant’s
roots
 Many roots, bugs, and
burrowing animals will
be in this layer
 Mostly made of humus,
water and air
 Mostly made of clay and
water
 Not much air makes it
down here because the
pore spaces filled with
water that trickled down
 Deeper roots reach down
from older trees to get the
water found there
 Not many bugs or smaller
creatures here because the
clay is so hard packed that
they cannot dig through
 Mostly made of
weathered parent
material (smaller to
larger sediments)
 Only the deepest roots
will reach down here for
the water that is there
 Few if any animals or
bugs because they
cannot dig through the
rocks
 This should be solid
bedrock to some
weathering towards the
top of the layer.
 No animals are here
because there is no air
and very little water
 Refers to the proportions of the different particles sizes
that are found in all soils
 Categories are based on the percentages of sand, silt
and clay
 The different textures can be found on a diagram
called the soil triangle