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Soils in kerala
Remote Sensing And Geographic Information System Applications (GL 223)
University of Kerala
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SOIL IN KERALA
This topo-lithosequence of Kerala along with variation in rainfall, temperature and alternate wet and dry conditions particularly from the western coast to high ranges in the east and swift flowing rivers lead to the development of different types of natural vegetation and soil. The soils of Kerala can be broadly grouped into coastal alluvium, mixed alluvium, acid saline, kari, laterite, red, hill, black cotton and forest soils. Based on the physico-chemical properties and morphological features the soil
of Kerala has been classified into 10 broad groups (Table 3). The major soil types of
1 alluvium
Soil along the coastal belt of the State soils are developed from marine deposits. The soil has originated from recent deposits, predominantly marine, with some fluvial sediment along the coast line. This soil is comparatively immature with high sand content and low water holding capacity with pH values less than 6 in most of the areas. The sand content is 82% with meager quantities of silt and clay. The soils is nearly neutral in reaction (pH 6) with loamy sand to sandy loam in texture.
These soils of marine origin are identified along the coastal plains and basin lands as a narrow strip. The elevation of the coastal area is generally below 5m MSL. The area has high water table and in some areas it reaches above the surface during rainy season. The soils of the coastal plains are very deep with sandy texture. The texture generally ranges from sand to loamy sand with greyish brown to reddish brown and yellowish red colour. Sand content ranges from 80% and clay up to 15%. Even though these soils have high water table, the water holding capacity is poor due to the predominance of sand. Coconut is the major crop in the area. Cashew and other fruit trees are also grown
2. Riverine Alluvium
This type of soil, developed along river valleys, occurs throughout the State cutting across the extensive laterite soils. The surface texture ranges from sandy loam to clay. It is very fertile having high water holding capacity and plant nutrients which are regularly replenished during floods. It supports cultivation of Paddy, Arecanut, Pepper, Tapioca and a wide variety of vegetables Red Loam This occurs mainly as colluvial deposits in isolated patches in foothills associated with laterites. The deep red colour of these soils is due to the presence of hematite and limonite ores. The rapid permeability of the surface soils is the common nature. The gravel content is nearly 5% with sand 65%, responsible for the development of this red loamy soils which are very deep in silt 18% and clay 12 % and Neyyattinkara taluks are characterized by these soils. The soil being highly porous and friable is not fertile.
3 alluvium soil
These soils are developed from fluvial sediments of marine, lacustrine and riverine sediments or its combinations. They occur below 20m MSL in the lowland plains, basins, valleys and along the banks
of major rivers. The mixed alluvium is mainly noticed close to coastal alluvium, Kuttanad and adjacent area and kole lands of Thrissur district. The soils are frequently flooded and submerged. The soils of depressions and broad valleys are subject to occasional flooding and stagnation. The ground water table of these soils is generally high and it reaches above the surface during rainy season. A wide variation in texture is noticed in these soils. Sandy clay loam to clay is the predominant texture. Sandy loam soils are also met with. Light grey to very dark brown is the common colour of the soil. Paddy, other annuals and seasonal crops like banana, tapioca and vegetables are grown here.
4 saline soil
Acid saline soils are present throughout the coastal area in patches with very little extent. Major area of this soil is identified in the coastal tract of Ernakulam, Thrissur and Kannur districts. The area under these soils comprise of low-lying marshes, waterlogged and ill drained areas near the rivers and streams, which are subject to tidal waves. Sea and backwater tides make these soils saline. During monsoon season, when rainwater and fresh water from rivers enter the fields, salinity is partially washed off. The area under these soils occur mostly on plains at or below sea level. A wide variation in texture from sandy loam to clay is noticed with dark grey to black colour. Paddy is the only crop that can be cultivated.
This soil found mainly in Kuttanad region,an area lying below sea level and submerged for the major part of the year. Salinity and water logging have put limitations to crop culture but with careful management, these soils can sustain good crop production. Paddy is successfully grown in this soil. This soil is grouped into three categories on the basis of morphological and physiochemical properties viz the Kayal soil (soil in reclaimed areas with high clay content) Kari soil (black soil with high organic content developed in low lying water logged areas), and Karappadam soil (soil along river courses with high silt content).
4. Kayal soil
This is formed from the Vembanad Lake and occupy about 8000 ha extending in the two districts of Kottayam and Alleppey. This soil will be submerged in water for 5-6 months in a year. As soon as the monsoon season ends, water is pumped into the canals, and rice is grown. The soil is slightly acidic to neutral with low organic matter and available nutrients. The texture ranges from silty loam to clay loam, with sand 50%, silt 20% and at around 28% is the clay.
4. Kari soils
This soil is located mainly in the Ambalapuzha, Vaikom and Cherthala taluks. It is deep, black, poorly drained, fine textured peat soils. The soil is extremely acidicin nature as the pH shows 3. They are rich in organic matter.
4. Karapadam soils
This soil occur along the inland water ways and rivers occuping a larger area of Kuttanad. It is river borne alluvial soils. The soil is very deep, poorly drained and dark grey with clay loam texture with 31% clay, 45% sand and silt 17%. The pH is 5 indicating the acidity of the soil which results in poor availability of the nutrients.
5 soil
These are found mostly in the southern parts of Thiruvananthapuram district and in pockets in catenary sequence along the foot slopes of laterite hills and mounds. These soils are identified in undulating plains of lowland with a general slope of 3 to 10%. These are mostly very deep and homogeneous in nature. The texture of the soil generally ranges from sandy clay loam to clay loam with red to dark red colour. Gravels are rarely noticed in these soils. A variety of crops such as coconut, arecanut, banana, yams, pineapple, vegetables, fruit trees etc., can be grown under proper management.
9 soil
The hill soils mostly occur above an elevation of 80m MSL. The area is hilly and has highly dissected denudational hills, elongated ridges, rocky cliffs and narrow valleys. The general slope range is above 10%. The texture of these soils generally range from loam to clay loam with average gravel content of 10 to 50%. In addition, stones and boulders are noticed in the subsoil. These soils have reddish brown to yellowish red/strong brown colour. Generally, increase in clay content is noticed down the profile. The depth of the soil varies considerably from 60 to 200 cm depending on the lie of the land, erodibility of soil and past erosion. These soils are mostly friable and subject to heavy soil erosion. The area is suitable for all dryland crops like rubber, coconut, arecanut and fruit trees based on the topography. Crops such as banana, pepper, pineapple, vegetables can be grown in foot slopes.
10 soil
These soils are developed from crystalline rocks of archaean age under forest cover. They occur along the eastern part of the State, generally above an elevation of 300m above MSL. The area is hilly and mountainous with steep slopes, escarpments, elongated rocky summits and narrow ‘V’ shaped valleys. The depth of the soil varies considerably depending on erosion and vegetative cover. The soils are generally immature due to slow weathering process. Rock outcrops and stones are noticed on the surface. Gneissic boulders under different stages of weathering are noticed in the subsoil. The texture of the soil ranges from sandy clay loam to clay with reddish brown to very dark brown colour. Forest trees, shrubs and grasses are grown here
Soils in kerala
Course: Remote Sensing And Geographic Information System Applications (GL 223)
University: University of Kerala
