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 The composition of soil differs for different types of soils. It depends upon different types of soils. It depends upon the type of rock from which the soil is the type of rock from which the soil is formed.formed.

The constituents of soil are :-The constituents of soil are :-

1.1. WaterWater

2.2. AirAir

3.3. Organic matter of HumusOrganic matter of Humus

4.4. Living OrganismsLiving Organisms

5.5. Inorganic matter and nutrientsInorganic matter and nutrients

6.6. MineralsMinerals

1. Composition of Soil in Water1. Composition of Soil in Water

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

2. Composition of soil in Air 2. Composition of soil in Air

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

33. Composition of soil in Organic matter . Composition of soil in Organic matter or Humusor Humus

The decomposition of dead The decomposition of dead organisms (plants. Animals. organisms (plants. Animals. Micro-organisms) adds organic Micro-organisms) adds organic matter to the soil. The excreta of matter to the soil. The excreta of organisms are also added to the organisms are also added to the soil.soil.

4. Composition of soil in Living Organisms4. Composition of soil in Living Organisms

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

5. Composition of soil in Inorganic 5. Composition of soil in Inorganic matter and nutrientsmatter and nutrients

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

6. Composition of soil in Minerals6. Composition of soil in MineralsDifferent minerals found in the soil are Different minerals found in the soil are

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

Soil is Natural Resource Soil is Natural Resource

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

Quality of SoilQuality of Soil

Soil may be coarse (sandy) medium (loamy) or Soil may be coarse (sandy) medium (loamy) or fine (clayey). The relative amount of primary fine (clayey). The relative amount of primary particles of sand. Silt and clay, determines the particles of sand. Silt and clay, determines the soil texture. The different types of soil particles soil texture. The different types of soil particles vary in size. Like –vary in size. Like –

a.a. Gravel particles – 2.0 to 5.0 mm in sizeGravel particles – 2.0 to 5.0 mm in size

b.b. Sand particles – 0.2 to 2.0 mm in sizeSand particles – 0.2 to 2.0 mm in size

c.c. Clay particles – less than 0.2 mm in sizeClay 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

a. Sandy Soila. Sandy Soil

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

b. Clayey Soilb. Clayey Soil

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

3. Loamy Soil3. Loamy Soil

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

Soil is Classified as six TypesSoil is Classified as six Types

1.1. Black SoilBlack Soil

2.2. Red soilRed soil

3.3. Laterite SoilLaterite Soil

4.4. Desert SoilDesert Soil

5.5. Mountain Mountain SoilSoil

6.6. Alluvial SoilAlluvial Soil

BLACK SOILBLACK SOILThis soil is created by the This soil is created by the

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

RED SOILRED SOILRed soil is created by the Red soil is created by the

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

LATERITE SOILLATERITE SOIL

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

DESERT SOILDESERT SOIL

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

MOUNTAIN SOILMOUNTAIN SOIL

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

ALLUVIAL SOILALLUVIAL SOIL

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

POLLUTION OF SOILPOLLUTION OF SOIL

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 POLLUTIONCAUSES OF SOIL POLLUTION

1.1. Different kinds of fertilizer and pesticides in Different kinds of fertilizer and pesticides in order to produce more, causes soil pollution.order to produce more, causes soil pollution.

2.2. Sand spreads over the field due to Sand spreads over the field due to flood and slain water of the ocean flood and slain water of the ocean pollute the soil.pollute the soil.

3.3. Except the industrial waste different Except the industrial waste different types of materials like lead, zinc, types of materials like lead, zinc, arsenic, cupper, cadmium dust from arsenic, cupper, cadmium dust from the mines also pollute the soil.the mines also pollute the soil.

4.4. Maximum use of plastic bags also Maximum use of plastic bags also pollutes the soil.pollutes the soil.

5.5. The various waste materials like The various waste materials like rubber, leather shoes, plastic covers rubber, leather shoes, plastic covers , polythene and leather shoes are , polythene and leather shoes are thrown outside and pollute the soil.thrown outside and pollute the soil.

6.6. The industrial waste also pollutes The industrial waste also pollutes the soil. The solid and liquid waste the soil. The solid and liquid waste from paper mills, ash from thermal from paper mills, ash from thermal power station, unrefined oil from oil power station, unrefined oil from oil refinery, acid mixed water from refinery, acid mixed water from leather and rubber industries leather and rubber industries pollute the soilpollute the soil