Soils of India Part II – Indian Geography
Forest & Mountain Soils
- These soils occupy about 2.85 lakh sq km or 8.67% of the total land area of India.
- They are mainly heterogeneous soils found on the hill slopes covered by forests.
- The formation of these soils is mainly governed by the characteristic deposition of organic matter derived from forests and their character changes with parent rocks, ground-configuration and climate.
- Consequently, they differ greatly even if they occur in close proximity to one another.
Distribution of Forest & Mountain Soils
- In the Himalayan region, such soils are mainly found in valleys, less steep and north facing slopes. The south facing slopes are very steep and exposed to denudation and hence do not support soil formation.
- Forest soils occur in Western and Eastern Ghats also.
Chemical properties of Forest – Mountain Soils
- The forest soils are very rich in humus.
- They are deficient in potash, phosphorus and lime.
- They require good deal of fertilizers for high yields.
Crops in Forest – Mountain Soils
- They are suitable for plantations of tea, coffee, spices and tropical fruits in peninsular forest region.
- Wheat, maize, barley and temperate fruits are grown
Arid & Desert Soils
- The desert soils consist of Aeolian sand (90 to 95 %) and clay (5 to 10 %).
- They cover a total area of 1.42 lakh sq km (4.32%).
- The presence of sand inhibits soil growth. Desertification of neighboring soils is common due to intrusion of desert sand under the influence of wind.
Distribution of Arid – Desert Soils
- Occur in arid and semi-arid regions of Rajasthan, Punjab and Haryana. The sand here is blown from the Indus basin and the coast by the prevailing south-west monsoon winds.
- Sandy soils without clay factor are also common in coastal regions of Odisha, Tamil Nadu and Kerala.
Chemical properties of Arid – Desert Soils
- They are usually poor in organic matter.
- Some desert soils are alkaline with varying degree of soluble salts like calcium carbonate.
- Calcium content increases downwards and the subsoil has ten times more calcium.
- The phosphate content of these soils is as high as in normal alluvial soils.
- Nitrogen is originally low but some of it is available in the form of nitrates.
Crops of Arid – Desert Soils
- Phosphates and nitrates make these soil fertile wherever moisture is available.
- There is a possibility of reclaiming these soils if proper irrigation facilities are available.
- In large areas, only the drought resistant and salt tolerant crops such as barley, cotton, millets, maize and pulses are grown.
Saline & Alkaline Soils
- In Saline and Alkaline Soils, the top soil is soaked or saturated with a substance with saline and alkaline salt particles
- Undecomposed rock fragments, on weathering, give rise to sodium, magnesium and calcium salts and sulphurous acid.
- Some of the salts are transported in solution by the rivers.
- In regions with low water table, the salts percolate into sub soil and in regions with good drainage, the salts are wasted away by flowing water.
- But in places where the drainage system is poor, the water with high salt concentration becomes stagnant and deposits all the salts in the top soil once the water evaporates.
- In regions with high sub-soil water table, injurious salts are transferred from below by the capillary action as a result of evaporation in dry season.
Peaty & Marshy Soils
- These are soils with large amount of organic matter and considerable amount of soluble salts.
- The most humid regions have this type of soil.
- They are black, heavy and highly acidic.
Distribution of Peaty – Marshy Soils
- It is found in Kottayam and Alappuzha districts of Kerala where it is called kari.
- it Also occurs in the coastal areas of Odisha, Tamil Nadu, Sunderbans of West Bengal, Bihar and Almora district of Uttarakhand.
Chemical Properties of Peaty – Marshy Soils
- They are deficient in potash and phosphate.
Crops of Peaty – Marshy Soils
- Most of the peaty soils are under water during the rainy season but as soon the rains cease, they are put under paddy cultivation.
What is Soil Erosion?
Washing or blowing away of the top layer of the soil is called soil erosion. Top layer of soil is the most fertile because it contains the most organic, nutrient-rich minerals . Soil erosion is caused by natural factors such as climatic conditions, temperatures and whether or manual factors such as ploughing of the field, over grazing, deforestation .
The process of soil erosion can be classified into 3 categories as follows
- when the loose soil particles are actually “detached” from the rest of the ground the process is called Detachment
- the topsoil is relocated to another area due to climatic conditions is known as Movement
- Deposition is where the eroded soils end up.
For example the forest area in uttarakhand due to extreme climatic conditions has land slide, the soil erodes and is washed away by rivers and drains into the ocean.
As mentioned, the predominant causes of soil erosion are either related to naturally-occurring events or influenced by the presence of human activity. Some of the principal causes of soil erosion include:
Causes of Soil Erosion
- Rain and rainwater runoff:In a particular heavy rain, soil erosion is common. First of all, the water starts to break down the soil, dispersing the materials it is made of. Typically, rainwater runoff will impact lighter materials like silt, organic matter, and finer sand particles, but in heavy rainfall, this can also include the larger material components as well.
- Farming:When land is worked through crops or other agricultural processes, it reduces the overall structure of the soil, in addition to reducing the levels of organic matter, making it more vulerable to the effects of rain and water. Tilling in particular, because it often breaks up and softens the structure of soil, can be a major contributor to erosion. Farming practices that reduce this activity tend to have far less issues with soil erosion.
- Slope of the land:The physical characteristics of the land can also contribute to soil erosion. For example, land with a high hill slope will perpetuate the process of rainwater or runoff saturation in the area, particularly due to the faster movement of the water down a slope.
- Lack of vegetation:Plants and crops help maintain the structure of soils, reducing the amount of soil erosion. Areas with less naturally-occurring flora may be a hint that the soil is prone to erosion.
- Wind:Wind can be a major factor in reducing soil quality and promotion erosion, particularly if the soil’s structure has already been loosened up. However, lighter winds will typically not cause too much damage, if any. The most susceptible soil to this type of erosion is sandy or lighter soil that can easily be transported through the air.