characteristics of soil | types of soil

 Unit 9 

       Soil

9.1 Characteristics of soil

Different soils have different characteristics. It is due to the nature and size of particles present in soil.Soil has  two main properties i.e. colour and texture.

Colour

Colour of the soil tells us about its and condition. Scientist have recognized about 170 different colours of soil but the most important colours are black, gray, brown and red.

The darken colour often indicates that there is more humus (decomposed matter of dead organisms) in it. Red clay is due to the availability of iron.

Texture

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Another property of soil is texture. It is determined by the size of particles in soil. There are three different types of soil on the basis of soil particles.

Some soils have more, large particles and less small particles. Some soils have more small particles and less large particles. Some soils have an equal amount of small and large particles.

 Soil containing equal amount of small and large particles is ideal for plant growth.

9.2 Types of soil

       There types of soil

•            Sandy Soil

•            Clay Soil

•            Silt Soil

 We know that the plants growing in a desert or at a hilly area are usually not found on plain areas. This is because different plants grow in different types of soil.

 Even if we collect soil samples from different places and analyze them. We can infer that one soil sample is different from the other. We can differentiate between types of soils on the basis of colour, particle size, texture and chemical nature. 

There are three main types of soils depending upon the size of particles. Other types of soil are the combination of these three types.

i:- Sandy soil

Sand consists of large particles. They cannot fit closely together, so there are large air spaces between them. Water moves through it very fast. It means that this soil does not hold water very well. 

When you rub sandy soil it feels rough. Soil which is made of 85% sand is called sandy soil. Very few plants grow in sandy soil. We see sand on beaches and in playgrounds.

ii. Clay soil

It consists of fine particles that pack tightly together. It has small air spaces. Water moves through it very slowly.

 It means that this soil holds lot of water.So it is difficult for the roots to get water into it. You generally find clay along the bank of river or stream.

iii. Silt soil

Silt is between sand and clay. It consists of particles of medium size. It has largest air spaces. It feels smooth and powdery. Water moves through it with medium speed. It means that this soil holds water more than sand. Gad is found as a deposit in river beds.

Other types of soil

•      Loam Soil

•      Chalky Soil

•      Peaty Soil

Loam soil

 Loamy soil is a compound of sand, clay and slit. It is the perfect soil for the development of the plant. The structure is trough and maintain water very easily. It contains more amount of humus.

Chalky soll

It consists of large number of lime stones. So it is alkaline in nature. It is poor for growing plants. Chalky soil is found in deep lime stone deposit.

Peaty soil 

It consists of lot of organic matter rich in water. It is also best soil for plant as it contains high water and nutrient contents. Peaty soil is found in marshy areas. This soil is formed in wet climate.

9.3 Components of soil

Soil of one place can be different to the soil of other place, but generally it consists of four basic components

1. Organic materials

2. Inorganic materials

3. Water

4. Air

1. Organic materials

The organic materials are decaying living matter. The dead plants or animals are decayed until they become part of the soil.

il. Inorganic materials

inorganic materials are the rocks that are broken down into smaller pieces. The size of the particles varies. It can appear as sand, gravel or as small as grains of sand or clay.

iii. Water

The amount of water in the soil is up close related to the climate and other characteristics of the region.

iv. Air

Air is the fourth basic component of soil. Air occupies some spaces of soil and water. It can make up approximately 2% to 50% of the soil volumes. Oxygen is essential for root and microbe respiration, which provide energy for plant growth. Carbon dioxide and nitrogen are also important for plant growth.

These components are found in the following proportion in the soil.

Soil has three layers

1. Top soil

2. Sub-soil

3. Gravel soil

Top soil is the upper most layer. Its colour ranges between grey and black. Sub-soil is middle layer. It is reddish or brown in colour. Gravel soil is the inner most layer. The particles of soil differ in size.

Soil with smaller particles absorbs more water. Soil has ability to absorb moisture and air. Moisture provides water to the roots of the plants.

 Air is also essential for the growth of the roots of plants and survival of soil animals. Good soil also contains different minerals such as nitrogen, phosphorus, potassium and calcium etc.