Soil and Ecosystems How Much Fertile Soil Does Earth Have?
https://www.youtube.com/watch?v=JBi21F9F6t0 Slide 2 Soil Essential
for Plants Terrestrial plants need soil to grow. Roots anchor
plants in soil. Roots absorb nutrients like nitrates, nitrites,
potassium and phosphorus from soil. Slide 3 Soil Profile The three
layers of the soil profile are topsoil, subsoil and bedrock. Slide
4 Three Layers of the Soil Profile 1. Topsoil mostly made of
decaying matter called humus. There are also small inorganic
particles and lots of living organisms like worms, bacteria and
fungus. Topsoil has the nutrients for plants. Slide 5 Three Layers
of the Soil Profile 2. Subsoil a very compact layer made mostly of
inorganic rock, sand and clay particles. 3. Bedrock this solid rock
means water cannot pass through. Can you see the layers? Have they
dug to bedrock? Slide 6 Water table When water reaches the bedrock
ground water forms. A well must be dug so that the tube goes below
the water table or the top surface of the ground water. Slide 7
Three Types of Topsoil The types of topsoil are determined by the
amount of humus and the amount of inorganic sand, clay and rock
particles. 1. Loam Soil the best soil for crops has lots of humus
and inorganic particles of different sizes for air pockets. Loam
holds water well and dries out slowly. 2. Clay soil the tiny clay
particles make root growth difficult and clay holds too much water.
3. Sandy soil Large sand particles let water flow through quickly
taking away nutrients and drying out too fast. Slide 8 Types of
Soil Good loam soil surrounds roots with humus, air, water and
nutrients in different sized particles of sand and clay. Slide 9
Which soil looks like loam to you? Slide 10 Human Actions Impact
Topsoil The roots of trees and plants prevent soil from eroding
with wind or rain water runoff. Deforestation leads to huge losses
of topsoil from rainwater runoff. Slide 11 Farming also leads to
soil degradation from use of pesticides that kill all the
microorganisms, or irrigation that adds a little more salt every
year. Human Actions Impact Topsoil Slide 12 If farmers apply excess
fertilizer or put fertilizer on the soil before it rains, the
fertilizer runs into rivers and lakes causing eutrophication. Human
Actions Impact Topsoil Slide 13 Humans can protect topsoil by
protecting forests. Good farming practices like crop rotation and
limited applications of pesticides can protect good quality
topsoil. Human Actions Impact Topsoil
