• The United Nations observes World Soil Day on December 5 as a means to focus attention on the importance of healthy soil and to advocate for the sustainable management of soil resources.

• World Soil Day 2023 and its campaign aim to raise awareness of the importance and relationship between soil and water in achieving sustainable and resilient agrifood systems. 

• An international day to celebrate soil was recommended by the International Union of Soil Sciences (IUSS) in 2002. Under the leadership of Thailand and within the framework of the Global Soil Partnership, Food and Agriculture Organisation of the United Nations (FAO) supported the formal establishment of WSD as a global awareness raising platform. The first official World Soil Day was observed on December 5, 2014.

• The date of December 5 was chosen because it corresponds with the official birthday of the late King Bhumibol Adulyadej, King of Thailand, who was one of the main proponents of this initiative.

Soil pollution is a major threat to human health

• Our planet’s survival depends on the precious link between soil and water. Over 95 per cent of our food originates from these two fundamental resources. 

• Healthy soil regulate water flow, filter pollutants, cycle nutrients, and support plant and animal diversity. Land and soil pollution dramatically disrupt this delicate balance, with far-reaching consequences on human and ecosystem survival.

• Soil has the ability to filter, buffer, retain and degrade contaminants, in which components such as soil organic carbon, organisms, pH or type of clays and other mineral complexes play a key role.

• Soil pollution is invisible to the human eye, but it compromises the quality of the food we eat, the water we drink, and the air we breathe and puts human and environmental health at risk. 

• Human activities over thousands of years have left a legacy of polluted soils worldwide. 

• In the face of climate change and human activity, our soils are being degraded, putting excessive pressure on our water resources. Erosion disrupts the natural balance, reducing water infiltration and availability for all forms of life.

• Soil pollution has been internationally recognised as a major threat. It affects the soil’s ability to provide ecosystem services, including the production of safe and sufficient food, compromising global food security.

• Improper disposal of hazardous and urban waste on soil, and exploitation of soil such as urban sprawl, industrial and transport activities, mining, military activities and armed conflicts, and unsustainable agricultural practices are the main sources of soil pollution caused by human activities.

• Soil pollution caused by anthropogenic activities is not limited to a well-delimited area (point-source pollution) but covers large areas (diffuse pollution), that, in some cases, can transcend national boundaries. 

• Virtually all countries and regions of the world have polluted soils, although their extent, dominant contaminants and level of pollution vary significantly depending on the level of industrialisation and the main sources of pollution.

• The cost of remediating polluted soils is high, both economically and environmentally, and requires advanced technologies. Especially in the case of diffuse pollution affecting large areas, management practices aimed at reducing the risk and entrance of contaminants into the food chain are applied.

• Sustainable soil management practices, such as minimum tillage, crop rotation, organic matter addition, and cover cropping, improve soil health, reduce erosion and pollution, and enhance water infiltration and storage. 

• These practices also preserve soil biodiversity, improve fertility, and contribute to carbon sequestration, playing a crucial role in the fight against climate change.

Different types of soils in India

On the basis of genesis, colour, composition and location, the soils of India have been classified into:

1) Alluvial soil

2) Black soil

3) Red and Yellow soil

4) Laterite soil

5) Arid soil

6) Saline soil

7) Peaty soil

8) Forest soil.

1) Alluvial soil

Alluvial soil is widespread in the northern plains and the river valleys. These cover about 40 per cent of the total area of the country. They are depositional soils, transported and deposited by rivers and streams. Through a narrow corridor in Rajasthan, they extend into the plains of Gujarat. In the Peninsular region, they are found in deltas of the east coast and in the river valleys. They are generally rich in potash, but poor in phosphorus. The colour of the alluvial soils varies from the light grey to ash grey.

2) Black soil

Black soil covers most of the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and some parts of Tamil Nadu. The black soil is generally clayey, deep and impermeable. They swell and become sticky when wet and shrink when dried. So, during the dry season, these soil develop wide cracks. Thus, there occurs a kind of ‘self ploughing’. Because of this character of slow absorption and loss of moisture, the black soil retains the moisture for a very long time, which helps the crops, especially the rain fed ones, to sustain even during the dry season. Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain potash. But they lack phosphorus, nitrogen and organic matter. The colour of the soil ranges from deep black to grey.

3) Red and Yellow soil

Red soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern part of the Deccan Plateau. Along the piedmont zone of the Western Ghat, a long stretch of area is occupied by red loamy soil. Yellow and red soil are also found in parts of Odisha and Chattisgarh and in the southern parts of the middle Ganga plain. The soil develops a reddish colour due to a wide diffusion of iron in crystalline and metamorphic rocks. It looks yellow when it occurs in a hydrated form. The fine-grained red and yellow soils are normally fertile, whereas coarse-grained soils found in dry upland areas are poor in fertility. They are generally poor in nitrogen, phosphorus and humus.

4) Laterite soil

Laterite has been derived from the Latin word ‘later’ which means brick. The laterite soil develops in areas with high temperature and high rainfall. These are the result of intense leaching due to tropical rains. With rain, lime and silica are leached away, and soil rich in iron oxide and aluminium compounds are left behind. Humus content of the soil is removed fast by bacteria that thrives well in high temperature. They are commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Odisha and Assam. They are poor in organic matter, nitrogen, phosphate and calcium, while iron oxide and potash are in excess. Hence, laterites are not suitable for cultivation. However, application of manures and fertilisers are required for making the soils fertile for cultivation. Laterite soil is widely cut as bricks for use in house construction. Red laterite soils in Tamil Nadu, Andhra Pradesh and Kerala are more suitable for tree crops like cashew nut.

5) Arid soil

Arid soil ranges from red to brown in colour. They are generally sandy in structure and saline in nature. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water. Due to the dry climate, high temperature and accelerated evaporation, they lack moisture and humus. Nitrogen is insufficient and the phosphate content is normal. Arid soil is characteristically developed in western Rajasthan, which exhibits characteristic arid topography. They are poor and contain little humus and organic matter.

6) Saline soil

They are also known as Usara soil. Saline soil contains a larger proportion of sodium, potassium and magnesium, and thus, they are infertile, and do not support any vegetative growth. They have more salts, largely because of dry climate and poor drainage. They occur in arid and semi-arid regions, and in waterlogged and swampy areas. Their structure ranges from sandy to loamy. They lack nitrogen and calcium. Saline soil is more widespread in western Gujarat, deltas of the eastern coast and in Sundarban areas of West Bengal.

7) Peaty soil

They are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation. Thus, a large quantity of dead organic matter accumulates in these areas, and this gives a rich humus and organic content to the soil. Organic matter in these soils may go even up to 40-50 per cent. They are normally heavy and black in colour. At many places, they are alkaline also. It occurs widely in the northern part of Bihar, southern part of Uttarakhand and the coastal areas of West Bengal, Odisha and Tamil Nadu.

8) Forest soil

As the name suggests, forest soil is formed in the forest areas where sufficient rainfall is available. The soil varies in structure and texture depending on the mountain environment where they are formed. They are loamy and silty on valley sides and coarse-grained in the upper slopes. In the snow-bound areas of the Himalayas, they experience denudation, and are acidic with low humus content. The soil found in the lower valleys are fertile.

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