Download - Soil
SOIL
What is the need of soil ?
It is needed for:-
Holding the roots firmly Supplying water and nutrients
Soil formation
Temperature changes Frost Water Wind Living organisms
WEATHERINGFactors responsible for weathering
Temperature changes
Rocks expand when heated and contract when cooled.
Frost
Rainwater may become trapped in small crevices of the parent rock. In winter this water freezes to ice. The ice expands producing a lateral pressure,causing the crevices in the rock to further open up.
Water
Continual movement of rain and river water, in liquid form,causes breaking down of rock particles into finer particles.
Interesting fact!
A rock has energy in several ways. Assuming it's sitting still, a rock may have gravitational potential energy because of gravity pulling on it. It has energy stored in the chemical bonds in the molecules of the rock. Also, if the rock has some charge on it(its a possibility), it could have electrical potential energy if it was in an electric field. Then of course there is the rest energy of the rock. According to relativity(E=mc^2), the rock has some energy just by being massive.
Interesting fact!
rocks do have potential energy. Potential energy is defined as energy stored within a physical system. It is called potential because it has the potential to be converted into other forms of energy, such as kinetic energy which can do work in the process.
This means that a rock can have potential energy as simple as, a rock held at an elevation. If dropped it's potential energy is then being converted to kinetic energy.
Wind
Wind blowing across a rock surface has an abrassive affect on the rocks.
Living organisms
Weathering by living organisms is called biological weathering
Soil profile
The term used for the vertical section of soil to show the different layers or horizons of soil.
A-horison-top soil
Darkest in colour Rich in humus Very fertile Soft,porous Roots of plants are present Living organisms are present
B-horizon-sub soil
Lighter in colour Harder and more compact than the A-
horizon Rich in soluble minerals and iron oxides Remains of plants and animals are not
found Roots of tall plants reach Little organic matter found
C-horizon-parent material
Beneath c-horizon is the bed rock
Composition of soil
Rock or different types of soil Humus Soil water Soil air Soil organisms
Soil particles and soil types
Soil particles-gravel ,sand and clay Soil types-loamy, clayey and sandy
Sandy soil
Highly porous Large particles Well aerated Holds less water Dry
Clayey soil
Very little air Particles are smaller and tightly packed Holds enough water Contains humus.
Loamy soil
Different sized particles Contain humus Hold sufficient water Contain enough air
Humus
Soil water
Gravitational water
Capillary water
Soil air
For the respiration of roots and soil organisms
Soil organisms
Earthworms burrow the soil Micro-organisms release the minerals
back to the soil Some bacteria fixes nitrogen
Soil organisms
Soil colour
White Grey Yellow Red Black
Soil and crops
Clayey soil -wheat ,gram and paddy Loamy soil -Lentils and other pulses Sandy soil -cotton
Clayey soil
Wheat paddy gram
Loamy soil
Sandy soil
Cotton
Soil erosion
Deforestation
Due to over population
Over grazing
Destroys vegetation Results in barren
land
Poor farming methods
Forest fires
After fire soil is exposed to wind and water
Prevention of soil erosion
Afforestation Plant trees along the boundaries of the
field Crop rotation Proper drainage and irrigation
Afforestation
Plant trees along the boundaries
To reduce the effect of winds
Crop rotation
Proper drainage and irrigation
Terrace cropping
Reduces the steepness Checks the soil erosion
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