What is the Nature of Soil? CBSE – NCERT Class 7 Science
In this article, we will discuss ‘Nature of the Soil’ ‘Soil horizon, and Soil profile’, ‘Different layers of Soil’ from Chapter 2- Soil out for Class 7 Science.
Nature of soil –
When rocks break down by the action of wind, water or any other source, it forms small particles which together form soil and this process of formation of soil is called weathering of soil. The various small particles are sand and rocks. Nature of a soil depends upon from which rock it has been formed that is the parent rock. For example, a rock which contains silica forms only sandy soil. Nature of a soil also depends upon the vegetation that has been grown upon it. For example, pedalfer a fertile and black soil forms where there is more of deciduous forest.
Fig. Formation of soil by weathering of rocks
Soil horizon and soil profile
- Different layers of soil are called soil horizons and the cross-sectional arrangement of these layers in soil is called soil profile.
- Each layer of soil has different texture and color, different depth and varying chemical composition.
- Layers of soil can be seen while digging a well or when the foundation of a building is laid.
- Humus is the rotting dead matter present in the soil which makes the soil fertile.
- Plants absorb their nutrients from the humus in the soil.
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Different layers of soil –
A- horizon- It is the topmost horizon and also called as topsoil. It contains a large amount of humus and minerals. Topsoil is soft and porous. The capacity of water retention is more of this soil and holds the roots of the plants entirely. Topsoil is the house of many living organisms such as worms, rodents, moles, and beetles.
B-horizon- B-horizon is the second layer of the soil profile and also called as a middle layer. It contains a larger amount of minerals than humus. The second layer is more compact and harder than topsoil.
C-horizon- The third layer of the soil profile. Small lumps of rocks are found with cracks and cervices.
Bedrock- It is the last layer of the soil profile. It is very hard and difficult to dig with a spade.
Fig. Soil profile- green part is A-horizon, brown part is B-horizon, next yellow layer is C-horizon and the rest of the last part is bedrock.
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Types of soil
Weathering of rocks form small particles of sand and clay. The amount of sand and clay in soil depend upon the parent rock from which the particles form. Soil can be also defined as the mixture of rock particles i.e. sand, clay, and humus. Based on the amount of various sized particles, soil can be divided into three types-
- Sandy soil-
When the soil contains a large number of big particles i.e. sand, the soil is called as sandy soil. Large sand particles have space filled with air in between the particles because these cannot pack closely. Water drain quickly thus sandy soils are light, mixed well with air, dry and have low water retention capacity.
Fig. Sandy soil
- Clayey Soil-
When the soil contains a large number of small particles i.e. clay, the soil is called as clayey soil. Small clay particles have little space for air because these pack closely and water can be easily held in the very small spaces. Clayey soils are heavy because of greater water-holding capacity than sandy soils; these are wet and not well aerated.
Fig. Clayey Soil
- Loamy Soil-
When the soil contains an equal amount of big and small particles i.e. equal amount of sand and clay, the soil is called as loamy soil. Along with sand and clay, another type of soil slit which is having a size in between sand and clay form loamy soils. It contains an appropriate amount of water for the growth of plants. Humus is also found in loamy soils. Loamy soils are wet, have great water retention capacity and well aerated. If the loamy soil contains more sand then the soil is light and if contains more clay then the soil is heavy.
Fig. Loamy Soil
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Tag: Nature of Soil, Soil horizon and soil profile, Different layers of soil, Types of soil, Class 7 Science