SOIL – 03 RED AND YELLOW SOILS
These are derived from granites, gneisses and other metamorphic rocks. These are formed under well-drained conditions. AREAS: Along the piedmont zone of the Western Ghat, a long stretch of area is occupied by red loamy soil. Yellow and red soils are also found in parts of Orissa 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. Often, their upper layer is red and the lower layer is yellow.
Varies from sand to clay and loam. Other Characteristic Features:
- The fine-grained red and yellow soils are normally fertile, whereas coarse-grained soils found in dry upland areas are poor in fertility.
- Have a porous and friable structure.
- They are generally poor in nitrogen, phosphorous and humus.
- These soils are airy and need irrigation for cultivation.
- Intense leaching is a menace in these soil areas.
The word Laterite has been derived from the Latin word ‘Later’ which means brick. These soils when wet are as soft as butter but become hard and cloddy on drying. Therefore, these are widely cut as bricks for use in house construction. FORMATION: The lateritic soils are particularly found on high flat erosion surfaces in areas of high(>200cm) and seasonal rainfall. The alternating wet and dry seasons lead to the leaching away of the siliceous matter of the rocks leaving behind the compounds of Iron And Aluminium.
These soils have mainly developed in the higher areas of the Peninsular plateau. The laterite soils are commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Orissa and Assam. Soil Colour: Reddish brown in colour due to the presence of iron oxide. Other characteristic features:
- With rain, lime and silica are leached away, and soils rich in iron oxide and aluminium compound are left behind(thus the reddish brown colour). Also, humus content of the soil is removed fast by bacteria that thrive well in high temperature.
- These soils represent the end product of decomposition and are generally low in fertility.
- The pebbly crust is the important feature of laterites which is formed due to alteration of wet and dry periods.
- These soils are acidic in character due to leaching. Application of manures and fertilisers is required for making these soils fertile for cultivation.
- These soils are poor in organic matter, nitrogen, phosphate and calcium, while iron oxide and potash are in excess.
Formation: These are derived from the disintegration of adjacent rocks and are largely blown from coastal regions and Indus valley. Areas: Arid soils are characteristically developed in Western Rajasthan, which exhibit characteristic arid topography. Soil Colour: Arid soils range from Red To Brown in colour. Soil Texture: They are generally sandy to gravelly in texture and have a high percentage of soluble salts. Other characteristic features:
- These are 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.
- These soils are deficient in nitrogen and humus. The phosphate and iron content is normal. These soils are rich in minerals but the main limitation is the lack of water.
- The soils exhibit poorly developed horizons.
- Plants are widely spaced.
- Chemical weathering is limited.
- Lower horizons of the soil are occupied by ‘kankar’ layers because of the increasing calcium content downwards. The ‘Kankar’ layer formation in the bottom horizons restricts the infiltration of water, and as such when irrigation is made available, the soil moisture is readily available for a sustainable plant growth.
If irrigated these soils give high agricultural returns. The availability of water from the Indira Gandhi canal has transformed the agricultural landscape of desert soils of western Rajasthan. These soils are mainly devoted To Bajra, Pulses, Guar, Fodder and less water requiring crops.
SALINE AND ALKALINE SOILS
They are also known as Usara soils. Various local names for saline soils are Reh, Kallar, and Chopan, Rakar, Thur, Karl etc.
- These soils have developed in areas with Dry Climatic Conditions (in areas having a little more rainfall than the areas of desert soils) accompanied by lack of proper drainage. In this situation, salts of sodium, calcium and magnesium are deposited on the upper layer of the soil by capillary action.
- In the Rann of Kuchchh, the Southwest Monsoon brings salt particles and deposits there as a crust.
- These soils are also formed when saline water spreads on the land at the time of high tide in coastal areas. Also, seawater intrusions in the deltas promote the occurrence of saline soils.
- Salinization also occurs because of over-irrigation (canal irrigation/groundwater use) and in areas of high water table (as in the coastal areas of Maharashtra and Tamil Nadu).
- Salinity from irrigation can occur over time wherever irrigation occurs. This is because almost all water (even natural rainfall) contains some dissolved salts. When the plants use the water, the salts are left behind in the soil and eventually begin to accumulate. Also, excessive irrigation with dry climatic conditions promotes capillary action, which results in the deposition of salt on the top layer of the soil
- The salt efflorescence of calcium, magnesium and sodium makes these soils infertile.
- Saline soils contain an excess of neutral soluble salts of chlorides and sulphates whereas sodic or alkali soils contain sodium carbonates/ sodium bicarbonates.
- They lack in nitrogen and calcium and have low water bearing capacity.
- These soils can be reclaimed by improving drainage, by applying gypsum and/or lime, and by cultivating salt resistant crops like barseem, dhaincha and other leguminous crops.
- The saline and alkaline soils may occur in any group of soils.
Formation: These are marshy soils and are a result of water logging and anaerobic conditions (which leads to partial decomposition of organic matter). Areas: They are found in the areas of Heavy Rainfall And High Humidity, where there is a good growth of vegetation. It occurs widely in the Northern Part Of Bihar, the southern part of Uttaranchal and the coastal areas of West Bengal, Orissa and Tamil Nadu. Soil Colour and Texture: These soils are normally heavy and black in colour Other characteristic features:
- These soils are characterised by a rich humus and organic content.
- There is a presence of iron and varying amounts of organic matter (10-40%). The organic matter in these soils may go even up to 40-50 per cent.
- These soils are generally acidic in nature. But at many places, they are alkaline also.
FORMATION: As the name suggests, forest soils are formed in the forest areas where sufficient rainfall is available. AREAS: These are found in the forest areas of Himalayas, Sahyadris, Eastern Ghats And Terai Region. SOIL COLOUR AND TEXTURE: The soils vary 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. Their Colour Is Dark Brown. Other Characteristics:
- In the snow-bound areas of the Himalayas, they are acidic with low humus content. This is because humus is rawer at higher levels. Also, these soils are subjected to denudation due to landslides and snowfall.
- The soils found in the lower valleys are fertile and rich in organic content.
- Owing to sharp differences of hill slopes and climates, these soils may differ greatly even when in proximity.
- Also, these soils exist in thin layers because of their development on the mountain slopes.
- These soils are poor in potash, phosphorus and lime.
- Soil erosion is a major problem in these areas.