Soil is the natural medium for the growth of plants under favorable conditions. Thorough knowledge of soil is essential to understanding its behavior towards vegetation. The type of natural vegetation is an expression of the prevailing soil condition. Any change in soil condition is reflected in vegetation types.
Soils of West Bengal
In an agrarian economy-dominated livelihood system, soil happens to be the first stage determinant to prioritize the choice for crop selection and productivity.
The soil of West Bengal is broadly divided into four types - Mountain soils, Alluvial soils, Red soils, and Saline soils.
As per the recent studies by the Department of Agriculture, the soil is categorized into six groups based on analysis of soil profile for:
- Mountain and Forest Soil
- Old Alluvial pre
- New Alluvial
- Red Soil
- Laterite Soil
- Saline Soil
Mountain and Forest Soil
The Northern region of West Bengal has mountain soil. This soil is formed by the process of weathering igneous and metamorphic rocks.
- It is less fertile and black in color.
- The soil is suitable for tea, pineapple, oranges, and pears cultivation.
- It is present at an elevation of 2550 m in the Darjeeling and Kalimpong districts.
- The region below the mountains, i.e. the duars, are thick forests that consist of forest soil.
- The forest soil has acidic humus and low base exchange capacity.
- In some areas, the forest soil is often sandy and gravelly, much coarser than the soils of the plains.
- It is present in Alipurduar, Jalpaiguri, and Coochbehar districts. Forest soil is also called Terai soil since it is present in the Terai region.
This soil is of comparatively old age and is also called Bhangar. This soil is distributed in the tract lying North of the Ganga containing the districts of North, South Dinajpur, Malda, Eastern Birbhum, and some parts of Murshidabad, Bankura, and Birbhum.
- It is suitable for paddy, wheat, and sugarcane cultivations.
- This soil is clayey in texture, acidic, rich in potash and phosphorus, and has a moderate amount of nitrogen and humus.
- The Barind area of Bengal consists of quasi lateritic alluvium.
This soil is comparatively newer than old Alluvial and is also called Khadar. This soil is found along the banks of the rivers.
- The soil is sandy loam to clayey in texture.
- New Alluvial soil is located in the plains of West Bengal, South of the Bhagirathi river up to the mouth of the Hooghly river. Murshidabad, Nadia, Howrah, and North 24-Parganas consist of new alluvium soil.
- It is suitable for paddy, wheat, and jute cultivation.
- This soil is very fertile as new organic material is deposited during floods that make the soil more fertile.
- The soil has high humus content, high water holding capacity, and is less acidic.
This soil is found in the districts of Birbhum, Bardhaman, Bankura, Midnapore, some parts of Malda, and Dinajpur.
- The presence of ferrous oxide makes the soil red, reddish-brown, or red-black in color.
- This soil has low water holding capacity. It is deficient in nitrogen, phosphate and high in potash and lime.
- This soil is mildly acidic and requires nitrogenous and phosphatic manuring.
- This soil is infertile in nature.
- Agriculture in this soil is practiced with the help of irrigation. Paddy is the chief crop grown in this soil.
This soil is found in the Western plateau region. This soil is found in the districts of Birbhum Bardhaman, Bankura, Purulia, Midnapore, some areas of Brain, and Madhupur forest areas.
- This sod is red in color.
- This soil is infertile, but with proper irrigation, little vegetation can be done in this soil.
- The laterite soil is acidic, poor in organic matter, calcium, phosphates, and nitrogen.
- Soil erosion leaching makes this soil infertile.
Clayey Saline Soil
The Sundarbans and the coastal areas of the state have this type of soil.
- The soil is bluish in color.
- It is acidic and has very loose particles due to excess organic matter.
- This soil is not suitable for cereal crop cultivation as it lacks the essential nutrients.
- It is ideal for the cultivation of plantation crops such as coconut, betel nut, and watermelon.
- It remains wet and saline for the most part of the year.
- This type of soil is present in the southern part of South 24 Parganas and Midnapore.
Soil Erosion in West Bengal
Soil erosion is the removal of the top layer of soil by different agents like wind, running water, etc. Many human-made factors cause soil erosion such as deforestation, overgrazing, faulty ways of agriculture, shifting cultivation, etc.
In West Bengal, around 20% of the land is degraded due to soil erosion and rendered unfit for agriculture. Major causes of soil erosion and preventive measures in West Bengal are:
- Sloping topography and heavy rainfall in the districts of Darjeeling, Kalimpong, Jalpaiguri, Alipurduar, and Coochbehar.
- Landslides, deforestation, shifting cultivation and excess siltation in mountain rivers increase the erosion of mountain and forest soil.
- Annual floods, waterlogging, prolonged wet and dry spells of rainfall, deforestation, faulty ways of cultivation are the leading causes of soil erosion in the delta plains of West Bengal.
- Coastal areas Waterlogging, high salinity, very poor water retention capacity, tidal waves, coastal runoff, excess siltation of rivers are the main causes of soil erosion in the coastal regions of West Bengal.
Preventive measures for soil erosion:
- Cultivation along the hill slopes
- terrace farming afforestation
- construction of dams
- strip cropping
- creating shelterbelts
- construction of drainage canals
- raising sea embankments
- making sea dykes
- planting trees (silviculture), etc.