Soils Class 7 Geography Notes Maharashtra State Board
The parent rock, the climate of the region, the biotic material, the slope of the land, and time are factors that influence soil formation.
Factors Necessary for Soil Formation
Remember that the parent rock in a region is an important factor in soil formation. Depending on the hardness of the rock and the climate of the region, the rock gets weathered. The rock turns into powdery material which further turns into earthy material. For example, the basalt rock of the Deccan Plateau in Maharashtra turns into black soil after weathering. This soil is also referred to as ‘regur’ soil. Rocks like granite or gneiss in South India give rise to red soil.
This is also an important factor influencing soil formation. Weathering of the rock is the first step in the process of soil formation. The process of weathering depends on the climate of the region. The climate decides the intensity of weathering. That is why the same type of rock gives rise to different types of soils when the rock is exposed to different climates. In the dry climate of the Deccan Plateau, weathering of basalt leads to the formation of black soil whereas in the humid climate of the Western Sahyadris, the leaching of the same basalt rock leads to the formation of lateritic soil.
The weathering of rocks turns them into powdery material but this powdery material is not soil. To turn such powdery material into soil, biotic material must be mixed into it. The biotic material comes from the decomposition of the remains of the plants and animals in that region. The vegetal litter, roots of plants, remains of animals, etc. get decomposed due to water. Microorganisms and certain other organisms help decompose the dead remains of organic materials. The biotic material thus produced gets mixed into the soils and is called ‘humus’. If the proportion of humus in the soil is greater, the soil becomes fertile. The process of decomposition by living organisms takes place continuously. Nowadays production of vermicompost is undertaken on a large scale. Try to understand the process of producing vermicompost or compost. Production of compost needs sufficient period and elements like organic waste, water, heat, etc.
Soil formation is a natural and slow process. It needs a very long period. To form a 2.5 cm thick layer of topsoil, it takes thousands of years. From this, you may understand that soils are invaluable. In the region of high rainfall and higher temperatures, the process of soil formation is faster. Comparatively, in regions of low temperatures and low rainfall soil formation takes more time. Humans use the soil gifted by nature as a resource. It is mainly used for agricultural purposes. For getting higher production, different types of chemical fertilizers, and insecticides are used profusely. However, this leads to the degradation of soils.
Earth Doesn’t Mean Soil:
Soil contains the powdered form of weathered rock, partially or completely decomposed organic material, and innumerable microorganisms. Interactions between biotic and abiotic components in the soil go on continuously. Plants get nutrients required for their growth from the soil. Soil is a complete ecosystem. Earth is also a substance. The potter uses it as raw material. A farmer uses soil as an ecosystem.
Take three flower pots of the same size. Keep one pot empty. Fill the second pot with water after closing the hole at the bottom and the third pot with soil. Put a few seeds in all of them. (You may use aserio, peas, gram, fenugreek, wheat, green gram, coriander seeds, etc.) Keep all three pots in the sun and water the empty pot and the soil-filled pot for 4-5 days.
An important component of the living world on Earth is ‘plants’. For the production and growth of plants, soil is indispensable. They provide support to plants. Vegetation is abundant in the regions that have fertile soils, e.g., the equatorial regions. However, in the areas where the soils are not fertile, vegetation is scanty, e.g., in deserts. And where there is a shortage of soil, vegetation is not seen, e.g., in the polar areas. Though favorable climate, availability of abundant water, and sunlight are necessary for the growth of a plant, these alone are not sufficient. Fertile soils favour plant growth.
When man realized that sowing seeds in the soil leads to the growth of plants and yields crops, he started using soil as a resource. Gradually, he realized that the fertile soils along the river beds give higher yields. Hence he settled in the valleys and started living there in groups. This led to the rise of ancient river valley civilizations, e.g., the Indus civilization. For the growing population, man started producing a greater amount of food crops. He realized that crop production and prosperity in agriculture mainly depend on the fertility of the soil and the optimum availability of water. Hence, there emerged competition among people to discover fertile lands and settle there. Later, for getting richer harvests he made efforts to increase the fertility of soils. In the process, the use of different fertilizers became a practice, which led to record agricultural production.
Food crops, fruits, and flowers are produced according to the type of soil. Food crops like jowar and bajra are produced in the regur soils of Maharashtra Plateau while soils in Konkan, Kerala, Tamilnadu, and Karnataka regions produce rice. In Madhya Pradesh, potato is cultivated in regions where the soils are well-drained. The local agricultural produce determines the staple diet of the people. The regions where soils are not arable need to fulfill their food requirements through import. For example, countries like Saudi Arabia, Qatar, Oman, etc. fulfill their requirements by importing food from China, India, and the USA.
The regions where soils are fertile can be self-reliant as far as food production is concerned. Hence, human settlements get concentrated in such areas. Agro-based industries flourish in these areas at a later date. For example, sugar factories develop in the sugarcane-producing areas; fruit processing industries develop in the areas of fruit production, etc. These regions later show signs of development.
You have studied the major soil types of Maharashtra. Based on the soil’s colour, texture, formation process, thickness of layers, etc. we can divide the State’s soils into 5 major types.
This soil type is a result of weathering and low rainfall. This soil can be found in the hilltops of the western part of the plateau, e.g., Ajanta, Balaghat and Mahadeo hills. The proportion of humus is negligible in this soil.
Regur or Black Soil:
It is found in areas of medium rainfall in the valleys and alluvial plains of river basins. Two types of this soil are found. Dark black soil is found in the western part of the Deccan Plateau while medium black soil is found in the eastern part (Vidarbha). Though it is black, the proportion of organic components is less in the soil.
This type of soil is found in the coastal belt of Konkan to the west of the Sahyadris and in the east of Vidarbha. In areas of very heavy rainfall, the eroded rocks get washed away in large quantities. As a result, the parent rock lies bare open. The iron in the rock reacts with the oxygen in the air and causes chemical reactions. This gives the reddish-orange colour to the soil which is thus formed.
Alluvial Soil of the Coastal Strip:
The majority of the rivers flowing in the Konkan region are short and flow with great speed. Therefore, the alluvium brought by them gets deposited at the mouth of the rivers. This soil is found at the mouth of the rivers in the western coastal strip, e.g., the areas around Panvel – Uran coast, Dharamtar Creek, etc.
Yellow Brown Soil:
These soils are found in areas of extreme rainfall. They are not very fertile. Therefore, they are not very useful for agriculture. They are mainly found in Chandrapur, the eastern part of Bhandara, and parts of the Sahyadri mountains.
Make two small heaps of soil. On one of them, sow or any other fast-growing seeds. Keep watering that heap for 4-9 days. After the saplings surface, water both the heaps with a watering can.
Soil Erosion and Degradation:
A layer of soil (top layer of soil) gets removed due to wind or water. This means that the soil gets eroded. Running water, climate, and diversity in physiography are reasons for soil erosion. The soil quality may be lowered due to certain reasons. This is called the degradation of soil. To obtain a higher agricultural yield, chemical fertilizers, insecticides, weedicides, etc. are used. The excessive spraying of chemicals and use of chemical fertilizers leads to soil degradation.
Excessive irrigation draws the salts from the soil upwards and makes the soil saline and then unproductive. Due to excessive use of chemicals, their residues remain in the soil for many years. They become a threat to the existence of microorganisms in the soils. It leads to a lowering of the humus content in the soil and the plants do not get micronutrients. If the pH of the soil thus gets disturbed it is a sign of soil degradation.
Geographic Indication (GI):
Certain soils are best suited for certain crops. Hence, crop production of that crop becomes the specialty of that area. Such crops are given the status of Geographic Indication (GI). For example, the hapus mango of Sindhudurg, custard apple from Beed district, the oranges of Nagpur, etc.
Considering the importance of soil, it is necessary to conserve it. It is necessary to protect the fertile soils of farmlands from getting washed out due to rains. Soil conservation includes the works like construction of embankments and, planting trees on them, the construction of gulley plugs against steep slopes, etc. Such works are taken up by the Department of Soil Conservation.
Planting trees can also control the velocity of the wind. This helps reduce the erosion of soil by wind. The plant roots hold the soil and this also reduces the erosion of soil. Under soil conservation, the continuous contour trenches (CCTs) are constructed along the slopes. Construction of such trenches at different heights checks the velocity of water running along the slopes and hence reduces soil erosion. The water arrested in these trenches percolates into the ground.
The Government of Maharashtra has implemented the watershed (catchment area) development program under which constructing embankments along slopes in rural areas, introducing CCTs along steep slopes etc. are undertaken. This led to the success of the scheme ‘Arrest water, let it percolate’. This has resulted in raising the groundwater levels and reducing the erosion of soil. Recently, the Government has launched a scheme called Jalayukt Shivar. Under this scheme, works like the construction of farm bunds, arresting waters of small streams, connecting the streams etc. are being carried out on a large scale.
It is advisable to reduce the excessive use of chemical fertilizers and pesticides. If organic manures, vermicompost, and compost are used regularly, it helps maintain the pH balance, increase the proportion of humus, and retain the fertility of the soil. Keeping the farmland fallow for some period and cultivating different crops alternatively is important to help retain the fertility of soils.
Comprehensive Maharashtra State Board Class 7 Geography Notes Soils can help students make connections between concepts.