SOILS

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SOILS:

ü  This is a natural body mineral and organic constituent.

ü  These layers are also called soil horizons.

ü  These layers are with variable thickness.

ü  The upper layers of soil are called Horizon.

ü  The bottom layers of soil are called bed rock.

ü  The main reason for soil formation is weathering.

ü  After the parent rock is broken the surface water enters into the inter spaces.

ü  Here the chemical change takes place and chemical substances are produced.

ü  With the death and decay of plants and bacteria the humus is produced.

Soil contains v  Mineral particles v  Humus v  Water v  Air v  Living Organisms (Bacteria)

ü  The layers differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics.

ü  It is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion.

ü  Soil is continuously interacts with the water, air etc.

ü  Because of this reason the soil differs from its parent rock.

ü  It is a mixture of mineral and organic constituents that are in solid, gaseous and aqueous states.

ü  Soil particles are packed loosely.

ü  Soil, a renewable resource.

ü  The soil structure is filled with pore spaces.

These pores contain soil solution (Water, petroleum etc) and air.

ü  Soil is also known as earth.

ü  Soil is referred to as regolith.

ü  Regolith means loose rock material.

ü  Soil contains mineral particles, humus, water, air, living organisms.

ü  Humus is an organic matter that has decomposed to a point where it is resistant to further breakdown or alteration

ü  Soil profile means the various horizons in the soil.

ü  Rains affect the minerals in the soil.

ü  The minerals are carried away by the rain.

ü  Soil mainly contains 4 basic compounds: Mineral Particles -  45% Water    -           25% Air -           25% Organic Matter -  5%

SOIL PROFILE:

·         The succession of horizons as viewed in the exposed Anatomy of the soil body is called soil profile.

SOIL PROFILE

SOIL HORIZON:

·         These are the specific layer in the land area that is parallel to the soil surface and possesses physical characteristics which differs from the layers above and below.

SOIL HORIZON

·         These Horizons are divided into O-P-A-E-B-C-D-R.

·         These are listed from top to bottom with in the soil profile.

·         All layers are not present in every location.

·         O-Horizon:

·         ‘O’ stand for Organic.

·         ‘O’ is a surface layer.

·         This layer is dominated by the presence of large amount of organic material.

·         P-Horizon:

·         ‘P’ stands for peats.

·         These are formed under water logged conditions.

·         P horizon is also highly organic.

·         A-Horizon:

·         This is the top layer of the soil.

·         A-Horizon contains humus.

·         This is dark in color.

·         The deeper layer of A-Horizon contains more organic material.

·         Most of the biological activities occur in A-Horizon.

·         Many types of warms and bacteria are concentrated here.

·         A-Horizon is also called bio mantle.

·         E-Horizon:

·         These are present only in the old soils.

·         These are present between A and B layers.

·         This layer is largely composed of silicates.

·         The O-P-A-E layers are collectively referred to as “solum”.

·         B-Horizons:

·         This is referred to as subsoil.

·         It consists of Iron and Aluminum.

·         This layer is also called Zone of accumulation.

·         This layer contains a very little Humus.

·         Plant roots penetrate through this layer.

·         C-Horizon:

·         This layer contains largely un weathered rock.

·         The parent material of the rock is present in this layer.

·         D-Horizon:

·         This is not universally distinguished.

·         Any soil material below the Solum and other than C-Horizon is referred to as D-Horizon.

·         R-Horizon:

·         This is the bed rock.

·         This is partially weathered bedrock at the bottom of the soil profile.

·         This contains continuous presence of rock.

TYPES OF SOILS:

ü  There are different types of soils on the earth.

ü  Depending on the content and the color, the soils are classified into various types.

ü  All soils are not suitable for all types of vegetation.

ü  This is the reason why all crops are not cultivated in one country or a region.

ALLUVIAL SOIL:

ALLUVIAL SOIL

ü  This is the most important soil.

ü  This derived from the word “Alluvium”.

ü  Alluvium means loose.

ü  Alluvial soil is made up of

v  Silt

v  Clay

v  Sand

v  Gravel

ü  Suitable for all types of crops.

ü  The Alluvium contains precious ores such as Platinum and Gold.

BLACK SOIL:

BLACK SOIL

ü  This is also called Black cotton soil

ü  This is suitable for cotton crop.

ü  This has the capacity to contain high moisture.

ü  This contains iron and aluminum. Hence the black color.

ü  This is very sticky when it is wet.

ü  During summer the black soil develops cracks.

RED SOIL:

RED SOIL

ü  This is porus and contains soluble salts.

ü  Red soil is deficient in Nitrogen, Humus and Phosphorus.

ü  This is suitable for the cultivation of rice, ragi, tobacco and vegetables.

ü  Groundnut and potatoes are grown also grown in red soils.

LATERITE SOILS:

LATERITE SOIL

ü  It contains iron oxides, and impart red colour to the soil.

ü  This is poor in Humus and Nitrogen.

ü  This is suitable for ragi, rice with application of manure.

ü  These soils are soft but harden when exposed to the atmosphere.

FOREST SOIL:

ü  This is deficient in potash, phosphorus.

ü  Tea, coffee, spices.

ARID AND DESERT SOILS:

ü  These are Rich in Phosphates.

ü  These soils are Poor in Nitrogen.

ü  If irrigation is provided they are quite fertile.

SALINE AND ALKALINE:

ü  These are also called Reh or kallar or usar.

ü  These types of soils are usually infertile.

ü  Salts are present in the upper layers.

ü  If drainage is provided they would be quite fertile.

PEATY:

ü  These are highly saline.

ü  Peaty soils are rich in organic matter.

ü  These are deficient in phosphorus and potash.

ü  These are not conducive for cultivation.

SOIL EROSION:

ü  The removal of the top layers of the soil is called soil erosion.

Causes for soil erosion: ·         removal of the forests ·         Wind ·         Rain ·         Floods

EROSION OF SOIL THROUGH WATER: ü  SHEET EROSION: When there is uniform rainfall over the slopes the soil cover is removed. ü  RILL EROSION: It occurs after the sheet erosion and the water enters the rock. ü  Gully Erosion: It happens with heavy rainfall. Gullies are formed.

SOIL CONSERVATION:

Soil Conservation is a set of management strategies for prevention of soil being eroded from the earth surface.

ü  Contour ploughing: This is a farming practice of ploughing across a slope following its elevation contour lines.

CONTOUR PLOUGHING

ü  Contour Bunding: This is similar to contour ploughing. Stones are placed around the contours of slopes.

CONTOUR BUNDING

ü  Terrace farming: This is also called step farming. This is used to cultivate the sloped land.Cutting like steps along the hill slopes. It reduces the speed of water.

TERRACE FARMING

ü  Strip cultivation: Cultivation of alternate strips of crops right angle to the prevailing direction of wind.

ü  Crop rotation: It helps in maintaining the fertility of the soil.

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