The study of chemical kinetics is essential in Chemistry Topics as it examines the rates of chemical reactions and the factors that influence them.
Characteristics and Importance of Types of Soil
We have just studied that in a good top-soil, gravel is present in very small amount. This means that the main rock particles present in the top-soil are sand, clay and silt. Now, the soils in different geographical areas contain different proportions of sand, clay and silt in them. They also contain different amounts of humus. In other words, the soils in different geographical areas will be different in compositions. So, depending on its composition, a soil can be classified as sandy soil, clayey soil or loamy soil. All these soils have different proportions of rock particles of different sizes. The sizes of rock particles in a soil have a very important influence on the properties of that soil. We will now discuss the various types of soils in detail.
Types of Soil
There are mainly three basic types of soils. These are: Sandy soil, Clayey soil and Loamy soil. The differences in the compositions of these three types of soil and their properties are discussed below.
1. Sandy Soil
Sandy soil contains mainly sand (having large particles with large spaces) (see Figure). It has hardly any clay or silt in it. Sandy soil contains very little humus. Sandy soil is found in desert areas.
Sandy soil has large particles with large spaces between them. 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. So, sandy soil dries out quickly which is not good for plants.
Sandy soil, however, provides good aeration (air) to the plant roots and it can be ploughed very easily. Sandy soil is light. It has a tendency to blow away if left bare. 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. Sandy soil is not sticky. Due to this, sandy soil cannot be used to make pots (like matkas and surahis, etc.), bricks, toys and statues.
2. Clayey Soil
Clayey soil contains mainly clay (having very small particles with very small spaces) (see Figure). It has hardly any sand or silt in it. Clayey soil also contains very little humus. Clayey soil has very good water-holding capacity due to its very small and tightly packed particles. Clayey soil is heavy because it can hold more water than the sandy soil.
The smallness of particles of clayey soil is also a disadvantage. This is because the water drains out very slowly through clayey soil which can lead to water-logging of soil and damage the crop plants. Moreover, due to the smallness of its pores, clayey soil is not able to trap enough air for the roots of the plants.
Clayey soil is compact and sticky due to which the ploughing of clayey soil is quite difficult. Clayey soil is, however, rich in minerals which is good for the growth of plants. 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.
Sand will improve the drainage of clayey soil whereas humus will provide it the necessary plant nutrients. Clayey soil is very sticky. Due to this, clayey soil is used to make pots (like matkas and surahis, etc.), bricks, toys and statues. In fact, clayey soil is the best soil for making pots, bricks, toys and statues.
3. Loamy Soil
Loamy soil is a mixture of sand, clay, silt and humus in the right proportions. Loamy soil is a mixture of large and small rock particles which impart it the desired properties. For example, loamy soil has the right water-holding capacity for the growth of plants. The excess water can also drain out through it easily. Loamy soil has also adequate air spaces between its particles to hold sufficient air needed by plant roots. Loamy soil can also be ploughed easily. 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. It is the best soil for growing crops. Loamy soil is also known as just ‘loam’.
From the above discussion we conclude that soils are classified on the basis of the relative proportions of rock particles of various sizes.
- If the soil contains greater proportion of big particles, it is called sandy soil.
- If the soil contains greater proportion of fine particles, it is called clayey soil.
- If the soil contains about the same proportions of large and fine particles, then it is called loamy soil (or loam).
Differences Between Sandy Soil and Clayey Soil
The main differences between sandy soil and clayey soil are given below :
- Sandy soil contains mainly big rock particles whereas clayey soil contains mainly fine rock particles.
- Sandy soil cannot hold much water but clayey soil has very good water-holding capacity.
- Sandy soil provides good aeration (air) to plant roots but clayey soil is not able to trap enough air for the roots of plants.
- Sandy soil is loose, light and non-sticky whereas clayey soil is compact, heavy and sticky.
- Sandy soil is less fertile whereas clayey soil is comparatively more fertile.
Soils And Crops
Different types of soils are found in different parts of India. In some parts of India, there is clayey soil, in some parts there is loamy soil whereas in other parts there is sandy soil. 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. Different types of crops grow well in different types of soils. Some of the important crops and the types of soils which are suitable for growing these crops are given below:
- 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, however, loamy soil. This is because loamy soil is rich in humus and very fertile.
- Soil rich in clay and organic matter, and having very good capacity to retain water is ideal for growing paddy (rice crop).
- For growing lentil (masoor dal) and other pulses, loamy soil which drains water easily, is required.
- 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 :
- Soil contains air.
- Soil contains water (or moisture).
- Soil can absorb water (or soak up water).
- Soil allows water to percolate (or pass down through it).
We will now perform some activities to study all these properties of soil, one by one.