Notes-Class-7-Geography-Chapter-7-Soil-Maharashtra Board

Factors necessary for soil formation

Soil formation requires the parent rock, the climate of the region, the biotic material, the slope of the ground, and time. These factors all have an impact on the soil formation process.

(i) Parent rock:

• Parent rock in a region is an important factor in soil formation.
• Depending on the hardness of the parent rock and the climate of the region, the parent rock gets weathered.
• The rock turns into powdery material which further turns into earthy material.

Examples:

• The besalt rock of the Deccan Plateau in Maharashtra turns into black soil after weathering. Black soil is also referred to as ‘regur’ soil.
• Rocks like granite or gneiss in South India give rise to red soil.

(ii) Regional climate :

• The intensity of weathering of rock depends on the climate of the region.
• The same type of rock gives rise to different types of soils when it is exposed to different climates.

Examples :

• In dry climate of Deccan Plateau, weathering of basalt leads to the formation of black soil.
• In the humid climate of the Western Sahyadris, the leaching of the same basalt rock leads to the formation of lateritic soil.

(iii) Biotic material :

• The biotic material comes from the decomposition of the remains of the plants and animals in a particular region.
• Many microorganisms and certain other organisms help in decomposition process. The decomposed biotic material gets mixed into the soils and is called humus.
• If the proportion of humus in the soil is greater, the soils become fertile.

(iv) Time :

• Soil formation is a natural and slow process.
• To form a 2.5 cm thick layer of top soil, it takes thousands of years.
• In the region of high rainfall and higher temperatures, the process of soil formation is faster.
• On the other hand, in the region of low rainfall and low temperatures, the process of soil formation takes more time.

Fertile soils :

Soil and Vegetation :

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.

Relation between soil and rise of civilization :

• In ancient times, man realized that sowing of seeds in the soil leads to the growth of plants and yields crops. Therefore, man started using soil as a resource.
• Gradually, man realized that the fertile soils along the river beds give higher yields.
• Therefore, man settled in the river valleys and started living there in groups.
• This further led to the rise of ancient river valley civilizations. For example, the Indus civilization.

Use of fertilizers for agricultural production :

• For the growing population, man started producing greater amount of food crops.
• For getting richer harvest, man made more efforts to increase the fertility of soils.
• In a process, he started using fertilizers that led to record agricultural production.
• For getting higher production, different types of chemical fertilizers, insecticides, etc. are used profusely, this leads to degradation of soil.

 Agricultural produce as per type of soils and diet :

• Food crops, fruits and flowers are produced according to the type of soils.
• The local agricultural produce determines the staple diet of the people.

Major types of soils in Maharashtra :

• Coarse soil : Coarse type of soil is a result of weathering and low rainfall. This soil can be found in the hilltops of the western part of Deccan Plateau and in Ajanta, Balaghat and Mahadeo Hills. The proportion of humus is negligible in this soil.
• Regur soil : Regur type of soil is also known as black soil. It is found in areas of medium rainfall in the valleys and alluvial plains of river basins. Dark black soil is found in the western part of Deccan Plateau while medium black soil is found in the eastern part of Maharashtra (Vidarbha)- Though it is black in colour, proportion of organic components is less in this soil.
• Laterite soil: Laterite type of soil is found to the west of the Sahyadris in the coastal belt of Konkan. It is also found in the east of Vidharbha. In areas of very heavy rainfall, the eroded rocks got washed away in a large quantity. As a result, the parent rock lies bare open. The iron in the rock reacts with oxygen in the air and causes chemical reactions. This chemical rcaction gives the redish-orange colour to the soil.
• Alluvial soil of the coastal strip : Majority of the rivers flowing in the Konkan region are short. These rivers flow with great speed. The alluvial brought by them gets deposited at the mouth of rivers. Alluvial soil of the coastal strip is mainly found at the mouth of the rivers in western coastal strip. It is found in the areas around Panvel, Uran coast, Dharamtar creek, etc.
• Yellow-brown soil : Yellow-Brown type of soil is found in the areas of extreme rainfall. This soil is very fertile in nature. Therefore, it is useful for agriculture. It is mainly found in Chandrapur, western part of Bhandara and parts of Sahyadri mountains.

Soil erosion and degradation

Soil erosion :

• A top layer of soil gets removed due to heavy rains or running water of rivers. The soil gets eroded due to high velocity of winds and steep slopes.
• Thus, soil erosion occurs due to running water, winds and slopes.

Soil degradation :

• The soil quality may get lowered due to certain reasons. This is called soil degradation
• To obtain higher agricultural yield, chemical fertilizers, insecticides, weedicides and irrigation technique is used. However, the excessive spraying of chemicals fertilizers leads to soil degradation.
• Excessive irrigation draws the salt from the soil upwards and makes the soil saline and then unproductive.
• Due to excessive use of chemicals, their residues remain in the soils for many years. They become threat to the existence of microorganisms in the soils. It leads to lowering of humus content in the soil and plants do not get micronutrients.
• In such condition, the proportion of humus in soil decreases and the pH value of soil gets disturbed. It is considered as a sign of soil degradation.

Soil conservation

Considering the importance of soils, it is necessary to conserve it.

Soil conservation works taken up by the Department of Soil conservation includes the works like

• construction of embankments
• planting trees of embankments
• construction of gulley plugs against the steep slopes.

The following are some of the measures of soil conservation :

• Tree plantation : Planting tress control the velocity of the wind. This help in reducing the erosion of soil by winds. The plant roots hold the soil firm and this also reduced the erosion of soil.
• Constructing Continuous Counter Trenches (CCTs) : Construction of CCTs at different heights checks the velocity of water running along the slopes and thus reduces soil erosion. The water arrested in CCTs percolates into the ground. This further helps in increasing the level of ground water.
• Watershed Development Program : The government of Maharashtra has implemented the Watershed (Catchment Area) Development Program. 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.
• Jalayukt Shivar : The government of Maharashtra has recently launched the scheme called ‘Jalayukt Shivar’. Under this scheme, works like construction of farm bunds, arresting waters of small streams, connecting the streams, etc. are being carried out on a large scale.