Soil is a natural body consisting of layers (soil horizons) of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics . Soil is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion. Soil differs from its parent rock due to interactions between the lithosphere, hydrosphere, atmosphere, and the biosphere. It is a mixture of mineral and organic constituents that are in solid, gaseous and aqueous states . Soil is commonly referred to as dirt. Soil particles pack loosely, forming a soil structure filled with pore spaces. These pores contain soil solution (liquid) and air (gas).Accordingly, soils are often treated as a three state system . Most soils have a density between 1 and 2 g/cm³.Soil is also known as earth: it is the substance from which our planet takes its name. Little of the soil composition of planet Earth is older than the Tertiary and most no older than the Pleistocene. In engineering, soil is referred to as regolith, or loose rock material.

WHAT IS SOIL?

Composition of soil soil is made up of different size of rock particle and humus. It has six component – rock particles , minerals ,humus , water, air and living organism. The smallest rock particles form clay ,little layer than clay particles are silt particles larger than silt are sand particles and the largest size of rock particle is gravel.

What are the main components of soil?

• Mineral Matter• Air• Water

• Organic Matter

How is soil created?Soil is created from rocks. Different natural factors like earthquake, stream of water, wind, ice and organic materials cause the rocks to break. Big rocks turn into pretty pebbles. Pebbles turn into sand and finally we get clay from the sand. Both sand, clay and different organic materials create soil.

We should ban polythene bags because polythene and plastic bags pollute soil .they also kill organisms living in soil .other substances which pollute the soil are a number of waste products ,chemicals and pesticides . Waste products and chemicals should be treated before they are released into the soil .The use of pesticides should be minimized . Polythene bags can best be defined as a non-biodegradable substance that is used by the majority as packing materials. Despite the fact that they are cheap as well as light, they are hazardous in the following ways;- The fact that they are non-biodegradable makes them hard to dispose and as a result, they can act as breeding places for many of the disease germs which, sooner than later cause an epidemic in the surrounding people.-The fact that they are very light also makes it very easy for them to be blown from place to place and as a result, the unending littering of the environment.-These polythene bags have over time been proven to be environmentally unfriendly considering the time taken for their decomposition. As a result of this time spun they can cause further problems like blocking water penetration into the soil which in turn affects food growth and development.Polythene are therefore the most outstanding of all the waste in the homes and are hard to dispose off.   

WHY SHOULD WE BAN POLYTHENE BAGS AND PLASTICS?

HUMUS :The dead remain of plant and animals in the soil is called humus.

Water: Water is 25% in the soil.

Clay: Clay soil is defined as soil that is composed of mostly clay particles. Soil that consists of over 50% clay particles is referred to as “heavy clay.” 

Sand: Sand is one of the oldest materials used to increase porosity by mechanically opening soils to air and water . The addition of enough sand to a stiff clay soil should, in theory, separate the particles so that air and moisture can move in freely and thus "correct" the soil.

Gravel: Gravel   is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. 

Layers of soil

Weathering and soil profileSoil is formed by the breaking down of rocks by the action of wind ,water and climate .this process is called weathering. A vertical section through layers of soil is called soil profile.

Soil formation greatly depends on the climate, and soils from different climate zones show distinctive characteristics . Temperature and moisture affect weathering and leaching. Wind moves sand and other particles, especially in arid regions where there is little plant cover. The type and amount of precipitation influence soil formation by affecting the movement of ions and particles through the soil, aiding in the development of different soil profiles. Seasonal and daily temperature fluctuations affect the effectiveness of water in weathering parent rock material and affect soil dynamics. The cycle of freezing and thawing is an effective mechanism to break up rocks and other consolidated materials. Temperature and precipitation rates affect biological activity, rates of chemical reactions and types of vegetation cover.

Climate

A – maximum accumulation of humus

B – maximum zone of accumulation/alterationC – zone of minimal accumulation / cementation

E – maximum zone of weathering/leaching

R – strongly cemented bedrock

O-  Litter layer of plant

O horizon: The "O" stands for organic. It is a surface layer, dominated by the presence of large amounts of organic material in varying stages of decomposition.A horizon: The A horizon is the top layer of the soil horizons or 'topsoil'. This layer has a layer of dark decomposed organic materials, which is called "humus".E horizon: is a mineral horizon in the upper part of the soil. Typically present only in forested areas it underlies an O or A horizon. B horizon: this layer is generally harder and more compact it has a lesser humus and more of minerals.C horizon: The C horizon is simply named so because it comes after A and B within the soil profile. This layer is little affected by soil forming processes (weathering).R horizon (bedrock): it is the last layer of soil which is difficult to dig.

Soil horizon

oA

E

B

C

R

TOP SOIL

SUBSOIL

Take some dry soil. Keep it in a metal container(katori) and heat it on a flame or over a candle cover it with a lid. You will observe drops of water on the inner side of the lid. For a better result, a metal tumbler or a heat resistant glass test tube can be used. You may conclude from this activity that even apparently dry soil also contains some water.

Activity 1Activity 1

 The proportion of big particles is relatively higher. The sand is well aerated as due to large particle size, they can not fit tightly to get her and have large spaces filled with air in between the particles. The sand is light in weight . The sand is almost dry as it can not retain water due to large particle size. Sandy soil is suitable for pee nuts and sandy-loam is for cotton crops. The clay particles exhibit properties of particles in colloidal state. This includes water retaining capacity as well . Cotton is grown in sandy soil because it drain water easily and can hold plenty of air. 

Sandy soil

Loamy soilThe best top soil for growing plants is  loamy soil is a mixture of sand ,clay and another type of soil particle One way of categorizing soil is by its texture: it may have the texture of sand, silt or clay . Its well-balanced properties, loamy soil is highly regarded for agriculture purposes is easy to work. A loamy soil is most suitable for plant growth as it contains some large particles to keep the soil porous and smaller particles for increasing its water holding capacity. Wheat, gram and other pulses are grown in loamy soil. 

1. The proportion of fine particles is relatively higher.2. The clayey soil is less aerated as clay particles, being much smaller, pack tightly together, leaving little space for air3. The clayey soil is heavy less air and more water content4. It can retain good amount of water in the tiny gaps between the particles of clay5. It is suitable for crops like Paddy, wheat and grams

Clayey Soil

Dig some soil from your garden or field. Put it in a glass tumbler or a wide mouth bottle filled with water, observe the evolution of air bubbles. You can repeat this activity by taking soils from different areas, like near a pond or near the drains. Make a comparison in the number of air bubbles evolved by taking some amount of soil from different places. This activity gives an idea that soil contains air.

Activity 2

The continuous transition of soil from a certain place in natural way is called soil erosion. It is caused by water and wind . Rain water , river current sea wave , strong wind etc are main sources of agent of soil erosion . Heavy rain separates the soil particle from the soil. This soil erosion happens at the two sides of river . Sea waves beating continuously at the shore wash away the soil from there . So soil erosion happens . In summer the dust blows away by the wind from the surface of the ground . Thus the soil becomes in sterile. The dust from the desert blows away by the soil erosion .At waste land and at the place without plant and trees, it causes by deforestation.

Soil erosion

Soil is very useful and very important natural wealth. It is formed in a natural process .The plants grow on the soil collecting water, mineral salt, cultivation is done on the surface of the earth. We can’t grow paddy , jute and wheat without soil. Besides this potatoes, ground nuts, ware also cultivated on the sandy soil. Vegetables are plenty cultivated on different types of soil. Beside this soil is used to build houses, roads and earth and to make pots. Different kinds of mineral wealth are also collected by digging the soil . Different kinds of micro organisms like ants, white-ants also live in the soil . Besides this cows, buffalos , camels and horses live on the land. So soil is very very useful to us. 

Soil as a natural resource

PERCOLATION

The rainwater getting absorbed by the soil due the gravitational pull is called percolation . This percolated water gets collected over the rock bed forming the water table . This is why ,the forest streams flow steadily even during the dry season .We can calculate the rate of percolation by using the following formula:Percolation rate ( ml/min)=amount  of water (ml)                                                percolation time(min)Percolation rate of water is different in different  types of soil it is  highest in the and least in the clayey soil.

Soil

THANKYOU

NAME: Shantanu tyagiCLASS –10SCIENCE