Types Of Soil

Question 1 Give few properties of sandy soil?

Question 2 Give few properties of clayey soil?

Question 3 Give few properties of loamy soil?

Question 4 Differentiate between clayey and sandy soil?

Question 5  State the important properties of soil?

Question 6 How will you calculate the percentage of water in a soil?

Question 7 How will you calculate the percolation rate of water in soil?

Question 8 Which type of soil is best for growing paddy?

Question 9 Which type of soil is best for growing lentils and other pulses?

Types of Soil

There are mainly three basic types of soils.

These are : Sandy soil, Clayey soil and Loamy soil.

 

Sandy Soil

1) Sandy soil contains mainly sand (having large particles with large spaces)

2) Sandy soil contains very little humus.

3) Sandy soil is found in desert areas.

4) Sandy soil has large particles with large spaces between them.

5) A disadvantage of sandy soil is that it cannot hold much water in it because the water gets drained out quickly through large spaces between its particles.

6) Sandy soil provides good aeration (air) to the plant roots and it can be ploughed very easily.

7) Sandy soil is less fertile. The fertility of sandy soil can be increased by adding humus to it in the form of manure. Humus improves the water-holding capacity of sandy soil and also supplies it necessary plant nutrients.

8) Sandy soil is not sticky. Due to this, sandy soil cannot be used to make pots ,bricks, toys and statues.

Clayey Soil

1) Clayey soil contains mainly lay (having very small particles with very small spaces)

2) Clayey soil also contains very little humus.

3) Clayey soil has very good water-holding capacity due to its very small and tightly packed particles.

4) Clayey soil is heavy because it can hold more water than the sandy soil.

5) Water drains out very slowly through clayey soil which can lead to water-logging of soil and damage the crop plants. 

6) Due to the smallness of its pores, clayey soil is not able to trap enough air for the roots of the plants.

7) Clayey soil is compact and sticky due to which the ploughing of clayey soil is quite difficult.

8) Clayey soil is rich in minerals which is good for the growth of plants.

9) Clayey soil is more fertile than sandy soil. The fertility of clayey soil can be improved by

adding some sand and humus (manure) to it.

10) Sand will improve the drainage of clayey soil whereas humus will provide it the necessary plant nutrients.

11) Clayey soil is very sticky. Due to this, clayey soil is used to make pots, bricks, toys and statues.

 

Loamy Soil

1) Loamy soil is a mixture of sand, clay, silt and humus in the right proportions.

2) Loamy soil is a mixture of large and small rock particles which impart it the desired properties.

3) Loamy soil has the right water-holding capacity for the growth of plants.

4) The excess water can also drain out through it easily.

5) Loamy soil has also adequate air spaces between its particles to hold sufficient air needed by plant roots.

6) Loamy soil can also be ploughed easily.

7) Loamy soil contains sufficient amount of humus. So, loamy soil has all the necessary nutrients for the growth of plants. Loamy soil is the most fertile soil.

(a) If the soil contains greater proportion of big particles, it is called sandy soil.

(b) If the soil contains greater proportion of fine particles, it is called clayey soil.

(c) If the soil contains about the same proportions of large and fine particles, then it is called loamy soil.

Differences Between Sandy Soil and Clayey Soil

Sandy soil	Clayey soil
It contains big rock particles	It contains mainly fine rock particles.
It cannot hold much water	It has very good water-holding capacity
It provides good aeration (air) to plant roots	It is not able to trap enough air for the roots of plants
It is loose, light and non-sticky	It is compact, heavy and sticky
It it is less fertile	It is more fertile

Soil and Crops

Soil is affected by the climatic factors such as wind, rainfall, temperature, light and humidity. The climatic factors as well as the type of soil determine the type of crops and other vegetation which can grow in a region.

Some of the important crops and the types of soils which are suitable for growing these crops are given below:

(1) Clayey soil and loamy soil are both suitable for growing cereals like wheat, and gram (chana). Such soils are good at retaining water. The best soil for growing wheat crop is,  loamy soil. This is because loamy soil is rich in humus and very fertile.

(2) Soil rich in clay and organic matter, and having very good capacity to retain water is ideal for growing paddy (rice crop).

(3) For growing lentil (masoor dal) and other pulses, loamy soil which drains water easily, is required.

(4) For growing cotton crop, ‘sandy-loam soil which drains water easily and can hold plenty of air in it, is more suitable.

 

Properties of soil

Some of the important properties (or characteristics) of soil are as follows:

1) Soil contains air

2) Soil contains water (or moisture)

3) Soil can absorb water (or soak up water)

4) Soil allows water to percolate (or pass down through it)

Soil contains air

Air is present in the spaces between the soil particles. This air provides the oxygen required for respiration by the roots of plants and other organisms (which live in soil).

The large spaces between sand particles are filled with air. Due to this, sandy soil provides much more air to the plant roots. Clay particles (being much smaller) pack tightly together leaving little space for air. So, clayey soil provides much less air to the plant roots which grow in it.

Soil contains water

Soil always contains some water in it which is called soil moisture.

Water is usually present as a thin film around the soil particles. The capacity of a soil to hold water is important for the growth of various crops.

If we pass through a farmland during a hot summer day, we will see that the air above the soil is shimmering. The soil in the farmland contains some water. On a hot summer day, this water of soil evaporates to form water vapour. The water vapour coming out of the soil reflects the sunlight irregularly due to which the air above the soil seems to shimmer.

Percentage of water (or moisture) in soil

(1) Take some soil and weigh it on a balance. This will give us the original mass of soil taken.

(2) Place this soil on a newspaper and keep it in bright sunshine to dry. Allow the soil sample to dry for about two hours. After drying, weigh the soil again on a balance. This will give us the mass of dry soil.

(3) Subtract the mass of dry soil from the original mass of soil. The difference in the mass of soil ‘before and after drying’ will give us the mass of water (or moisture) present in the original mass of soil taken.

The percentage of water (or moisture) in the given sample of soil can then be calculated by using the formula :

Percentage of water in soil =( Mass of water in soil / Original mass of soil) × 100

Soil can absorb water

Though soil usually contains some water (or moisture), it can still absorb (or soak up) a lot of water.

Soil allows water to percolate

When water is poured over soil, then some of it gets absorbed in the soil and the rest passes down the soil. The process in which water passes down slowly through the soil is called percolation of water. 

Though water can percolate through all types of soils but the rate of percolation of water through different types of soils is different.

To Measure the Percolation Rate of Water in Soil

The percolation rate of water in a soil is the volume of water in millilitres which passes down the soil per minute. The percolation rate of water in a soil can be measured as follows.

(1) Take a 20 cm long PVC pipe having a diameter of about 5 cm. At the place where percolation rate of water is to be measured, dig the soil to a depth of about 2 cm in the ground. Place one end of the pipe in the dug up ground and hold it vertically. Fill a measuring cylinder with water. Note the volume of water taken in the measuring cylinder.

(2) Pour the water taken in the measuring cylinder in the pipe slowly from the top end. Note the time when you just start pouring water in the pipe.

(3) After some time, all the water poured in the pipe will percolate down through the soil, leaving the pipe empty. Note the time again when all the water has percolated down through the soil and the pipe becomes empty.

(4) The difference in the two ‘time readings will give us the time taken by the water taken in the measuring cylinder to percolate into the soil.

 

Percolation rate of water in soil = Volume of water percolated in soil/ Time taken for percolation

The percolation rate of water is expressed in the unit of millilitres per minute which is written in short form as mL/min.

1) Sandy soil is quite loose, so the percolation rate of water is highest in sandy soil.

2) Clayey soil is very compact. So, the percolation rate of water is lowest in the clayey soil.

The sandy soil (having the highest percolation rate) allows the rainwater to reach a well faster and in greater amount. Sandy soil retains the least rainwater in it. 

The clayey soil (having the lowest percolation rate) retains the highest amount of rainwater in it.

Paddy (rice crop) is planted in standing water in the fields. Paddy also requires a lot of irrigation water afterwards. The soil with a low percolation rate of water would be the most suitable for growing paddy (rice crop) because it will allow the water to remain in the fields for a much longer time.

All the plants growing on the surface of earth are called vegetation. Vegetation includes green grass, herbs, shrubs, bushes, crop plants as well as trees. It is the fertile top-soil of the earth which makes the vegetation grow.