Soil is one of the most important natural media which support the growth of plants.
Soil is, a complex mixture of several components. Various physical, chemical and biological activities take place continuously in the soil. Let’s discuss about the formation of soil, constituents of soil and their utility.

The composition of soil differs for different types of soils. It depends upon the type of rock from which the soil is formed.
The constituents of soil are :-
1. Water
2. Air
3. Organic matter of Humus
4. Living Organisms
5. Inorganic matter and nutrients
6. Minerals

Water is generally found in all types of soils. Plants do not grow in dry soils.
Soil water is present between and at the surface of soil particles.

Air is present in the spaces between soil particles. The amount of air present varies from soil to soil. Soil texture from the atmosphere above the ground in the sense that it is normally lower in oxygen content and higher in carbon dioxide content. Soil air is needed for the respiration of plants.

3 . Composition of soil in Organic matter or Humus
The decomposition of dead organisms
(plants. Animals. Micro-organisms) adds organic matter to the soil. The excreta of organisms are also added to the soil.

4. Composition of soil in Living Organisms
Various kinds of living organisms are present in the soil. These include microflora (bacteria, actinomycetes, algae and fungi) and microfauna (protozoa, nematodes, insects and other organisms).
You might have noticed earthworks and ants coming out of the soil during rainy season.

5. Composition of soil in Inorganic matter and nutrients
Soil gets inorganic nutrients from the parent rock from which it is formed. The whole process of soil formation is generally divided into two stages i.e., weathering and soil development. The process of weathering involves the breakdown of bigger rocks into smaller mineral particles. Mineral particles are modified into different soil types through interaction between biological, climatic and other factors. Inorganic nutrients are also added to the soild from time to time in the form of manures and fertizers. Plants do not develop well in the absence of these nutrients. The inorganic matter of the soil is the combination of minerals and inorganic salts.

6. Composition of soil in Minerals
Different minerals found in the soil are called nutrients. Plants require at least sixteen different nutrients for their growth. Some of these nutrients are needed in large amounts and are called macronutrients. The macronutrients required for the growth and development of plants are carbon.
Hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. The macronutrients are also called major elements or microelements.
Among the nine macronutrients, nitrogen, phosphorus and potassium are needed in greater amounts then the others. These three are called primary nutrients
.

Soil is Natural Resource
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.

Quality of Soil
Soil may be coarse (sandy) medium (loamy) or fine (clayey). The relative amount of primary particles of sand. Silt and clay, determines the soil texture. The different types of soil particles vary in size. Like – a.
b.
c.
Gravel particles – 2.0 to 5.0 mm in size
Sand particles – 0.2 to 2.0 mm in size
Clay particles – less than 0.2 mm in size

Pore space
Soil particles
Molecular layer of water
Particles
Depending on the amounts of different particles, soil can be classified into three groups a.Sandy Soil b.Clayey Soil c. Loamy Soil

Sandy soil contains 70-85% sand and some clay. Due to bigger-sized particles, sandy soil does not have good waterholding capacity. There is a lot of air present in this soil. Sandy soil is not suitable for the growth of plants.

In this soil, a high percentage of clay, very less sand and some amount of humus are present. This soil is better than sandy soil for the growth of plants. There is no air in this soil. Clayey soil has a very good water-holding capacity.

Loamy soil is made up of sand, clay and humus. This soil had good water- holding capacity and air is also found in the Soil. The plants also obtain optimum quantities of mineral salts from this soil. Loamy soil is the best for the growth of plants.

3.
4.
1.
2.
5.
6.
Black Soil
Red soil
Laterite Soil
Desert Soil
Mountain Soil
Alluvial Soil

This soil is created by the discharges of
Volcanoes. One can find magnesium and iron in it.
It is very useful for the production of cotton and sugar-cane. It can keep water very well. This soil is available in Maharastra, Andhrapradesh,
Madhyapradesh and Gujarat.

Red soil is created by the erosion of Igneous rock. It looks red as there enough iron-oxide.
This soil is very fertile as it is constituted by small ingridents. This soil can be found in
Tamilnadu, Karnataka, Andhrapradesh, Orissa
& Jharkhand.

This is red color.This is a mixture of clay and pretty pebbles in it. It is sterile and not fit for agriculture.This soil can be found in the mountainous regions of Orissa, Karnataka,
Kerala and Assam.

This soil is mainly constituted by the mixture of sand. There is no organic materials in this soil.
This soil can not be used in agricultural purposes due to lack of water. This soil is seen in the dry regions of India like Rajasthan, Punjab and
Hariyana.

This soil is created by the decomposition of dry leaves and organic materials. It is very fertile as it is mixed with organic materials.
This soil can be found in the mountain regions of Mahalaya, Arunachal Pradesh and Jammu
& Kashmir.

This soil is stored in the river valley or low lands of the plateau or higher regions. It is very fertile. One can find clay, sand and small pretty pebbles in it. It is found in Uttarpradesh,
Hariyana, Bihar, WestBengal &
Andhrapradesh.

Soil pollutes like air and water. The microbes, animals and plants are affected with the polluted soil.
Plants and crops do not grow in the polluted soil. The fruits, vegetables and crops produced from the affected soil are also polluted.

CAUSES OF SOIL POLLUTION
1.
2.
3.
Different kinds of fertilizer and pesticides in order to produce more, causes soil pollution.
Sand spreads over the field due to flood and slain water of the ocean pollute the soil.
Except the industrial waste different types of materials like lead, zinc, arsenic, cupper, cadmium dust from the mines also pollute the soil.

4.
5.
6.
Maximum use of plastic bags also pollutes the soil.
The various waste materials like rubber, leather shoes, plastic covers , polythene and leather shoes are thrown outside and pollute the soil.
The industrial waste also pollutes the soil.
The solid and liquid waste from paper mills, ash from thermal power station, unrefined oil from oil refinery, acid mixed water from leather and rubber industries pollute the soil