SOIL• What is Soil?• **********• The mixture of rock particles and

humus is called the soil.• Soil is one of the most important

natural resources .It supports the growth of plants by holding the roots firmly and supplying water and nutrients.

• It is the home for many organisms.

• Soil is essential for Agriculture.• It provides food,clothing and

shelter for all.

SOIL PROFILE

• Soil is composed of distinct layers.A vertical section through different layers of the soil is called the soil profile.

• Each layer differs in texture, colour , depth

and chemical composition.These layers are referred to as HORIZON.

A-HORIZON

• A-HORIZON(TOP SOIL)• *********************• The uppermost horizon is called A-horizon or top

soil.• It is dark in colour and rich in humus(the rotting

dead matter in the soil ) and minerals.• It is fertile and provides nutrients to growing plants.• It is generally soft,porous and can retain more water.• It provides shelter for many living organisms such as

worms,rodents,moles and beetles.

B-HORIZON

• B-HORIZON(MIDDLE LAYER)

• ***************************

• This layer has a lesser amount

of humus but more of minerals.

• This layer is generally harder

and more compact.

C-HORIZON

• C-HORIZON

• ***********

• This layer is made up of small lumps of rocks with cracks and crevices.

BEDROCK

• BEDROCK• *********

• This is the innermost layer of the soil profile.

• It is very hard.• It is very difficult to dig with a spade as it is

made up of only rocks.

TYPES OF SOIL

• The soil is classified on the basis of the particles of various size.

• It is of three types-• 1-Sandy soil• 2-Clayey soil• 3-Loamy soil

SANDY SOIL

• If soil contains greater portion of big particles it is called as sandy soil.

• Sand particles quite large .• They cannot fit closely

together,so there are large spaces between them.These spaces are

filled with air . Water can drain quickly through

these spaces . So, sandy soil tend to be

light ,well aereated and rather dry.

CLAYEY SOIL

• If the portion of fine particles is relatively higher then,it is called Clayey soil.

• Clay particles being much smaller,packed tightly together leaving little space for air.

• Unlike sandy soil ,water can be held in the tiny gaps between the particles of clay.So clay soils have little air but they are heavy as the hold more water than sandy soil.

LOAMY SOIL• If the amount of large and

fine particles is about the same then the soil is called loamy soil.

• The best top soil for growing plants is loam.

• Loamy soil is a mixture of clay,sand and another type of soil particles called as Silt.

• Silt occurs as a deposit in river beds.The size of silt particles is between those of sand and clay.

• The loamy soil has humus in it.It has right water holding capacity for the growth of plants.

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SMT PRABHASINI PANDA

SC TEACHER