Define Soil or what is exactly soil?
Soil is a mixture of minerals,organic matter,gases,liquids and countless organisms that together support life on earth.
Another Definition of Soil is the organic and inorganic materials on the surface of the earth that provide the medium for growth plant.
Soil is also called the “Skin of the earth” as soil interfaces with the lithosphere, the hydrosphere, the atmosphere and the biosphere and thus helps in the growth of plants.
What are Inorganic Materials?
Inorganic materials are those materials which are not living, include minerals and whethered rocks
What are Organic Materials?
Organic materials are substances in the soil that were once alive. Examples are dead plants, animals, bacteria and fungi are all examples of organic material.
Study of Soil
The term given for study of soil is “Pedology”.
Pedology is the study of soil in their natural environment.It is one of the branches of soil science, the other being edaphology.
What is Pedology?
Pedology deals with pedogenesis, soil morphology and soil classification.
In simpler words, pedology studies the origin of the soil,the classification of soils and description of the soils.
What is Edaphology?
Edaphology studies the way the soils influence plants, fungi and other living organisms.
What are the Classifications of Soils?
The soil,in fact is different in each area of the world and has its own climate,rocks and vegetation and therefore,its own soils, with unique characteristics.
So the Classification of Soils have been evolved by a number of systems for categorizing various types of soils.
In the below sections, soils are classified on various basis such as
Ancient Classification of Soil
Modern Classification of Soil – ICAR – Indian Council of Agricultural Research
Classification Based on the texture of Soil
Classification done by USDA (United States Department of Agriculture)
Urvara and Usara – Classification of Soil based on Ancient Period
The soil during the ancient period was classified based on a simple condition whether the soil is fertile or infertile.
The classification were
What is the difference between Urvara and Usara soil?
Urvara is a fertile type of soil and Usara is a infertile type of soil.
What are Sterile Soil?
Usara is also called “Sterile soil” which means infertile.
The classification of soil on the basis of the ancient period was a brief one.But the actual classification of soils in India happened during the modern classification.
What are the modern Classification of Soils in India?
When human beings started to know about the various characteristics of soil, they began to classify the soils on the basis of slope,texture,color,moisture etc.
Several Agencies were involved for classifying the soils in the modern period.
- Soil Survey Of India (SSI)
- National Bureau of Soil Survey and the land use planning (NBSS & LUP)
The Soil survey of India was established in 1956.The soil survey of India studied soils of India and their characteristics.
National Bureau of Soil Survey and the Land Use Planning is an institute under the control of Indian council of Agriculture Research (ICAR) did a lot of studies on Indian Soil.
Classification of Soils in India on the basis of ICAR are
- Alluvial soil
- Red Soil
- Black Soil
- Arid Soil
- Laterite Soil
- Saline Soil
- Peaty/Marshy Soil
- Forest and Mountain Soil
How Soils in India are formed?
How Alluvial Soil is formed?
Alluvial soil is formed by the deposition and transportation of silts and sediments bought down by the rivers while flowing through the mountains.
In geology,something made up of or found in the materials that are left by the water of rivers, floods etc.Hence, these soils are named as alluvial soils.
How Black Soil is formed?
Formed due to solidification of lava spread over large areas during volcanic activity in the Deccan plateau thousands of years ago.
How Red Soil is formed?
Formed due to decomposition of ancient crystalline rocks like granites and gneiss and from rock types rich in minerals such as iron and magnesium. The term “red soil” is due to wide diffusion of iron oxides through the materials of the soils.
How Laterite Soil is formed?
The alteration of wet and dry season leads to the leaching away of siliceous matter and lime of the rocks and the soil rich in oxides of iron and aluminum compounds is left behind.
How Peaty and Marshy soils are formed?
Originate in the humid regions as a result of accumulation of large amounts of organic matter in the soil. They contain considerable amounts of soluble salts and 10-40% of organic matter.
How Desert Soils are formed?
Desert soil form in arid climates , where evaporation is five times more than annual precipitation from rain and snow.
How saline and Alkaline soils formed?
Some of the salts are transported in solution by rivers and canals , which percolates in the sub- soils in the plains.
How Forest and Mountain soil is formed?
Soil type of mountains are mainly found in hill slopes are mainly formed by deposition of organic matter from woodlands and forests. Mountain soils are generally located in the dry and cold districts like Ladakh, Lahaul and Spiti District , Kinnaur District etc.
How Soils are classified based on the Texture?
The classification is based on the basis of particle sizes and composition of soil.
These are “sand”,”slit”,”clay” and then there is a fourth texture called “loam”.
What is clay or what is clayey soil?
Clay usually consists of particles less than 0.075mm in size.It is a sticky soil and shows great changes in volume with variation in its water contract.It also shows considerable strength when air dried.
What is silt or what is silty soil?
Silt are larger particles than clay and are mainly inorganic in nature.The particle size is less than(<) 0.075mm in size and exhibits plastic or non-plastic behavior.
What is sand or what is sandy soil?
Sand, by its comparative large size does not have chemical valance.So there is no chemical activity.Sand drains easily, as it has poor ability to retain moisture.
Sand is generally present in a seashore, desert and bank of a river.
What is loam or what is loamy soil?
Loam is used to describe a roughly equal concentration of sand,silt and clay.In other words, loam is a mixture of sand,silt and clay in different proportions.
Classification of Soils based on United States Department of Agriculture(USDA)
USDA have classified the soil into 12 types as shown in the diagram below
Soil Formation in India
The formation of soil is a long process that is continued over thousands of year.The weathering of rocks and minerals initiates the formation of soil.The rocks on the surface breaks down into smaller pieces through the process of weathering and is mixed with organic matter and over time this forms a thin layer of soil.
Plants attract animals and when animals die, their bodies decompose.This decomposition makes the soil rich and thick.
But there are a number of factors responsible for soil formation in India.So lets go through one by one.
What are the factors responsible for the formation of Soil in India?
Factors Responsible for soil formation in India
- Parent Material
- Relief or Slope
- Natural Vegetation.
As the name suggests, the soil formed is derived from the rocks of its parent.The parent material are termed by soil scientists.
The parent material helps in determining the
- soil color
- minerals in the soil
- texture of the soil i.e,whether the soil is clayey,loamy,sandy or silty
In India,parent material are categorized into six classes:
- Ancient crystalline and Metamorphic rocks.
- Cuddapah and Vindhyan rocks
- Gondwana rocks
- Deccan basalts
- Tertiary and Mesozoic sedimentary rocks of extra peninsular India
- Recent and sub-recent rocks
Relief or Slope
Relief influences the formation of soil in many ways.But the most important being the slope of the land.
For example , chambal ravines that flows between Rajasthan and Madhya Pradesh which contains a steep slope making the flow of rivers to flow faster, which results in the hindrance of soil formation and there is a chance of occurrence of soil erosion.Thus steep slope causes soil erosion.
On the other hand,gentle slope or low relief also largely determines the fertility of the soil.You can set the alluvial soils as an example, as it contains thick layers, which makes the alluvial soil deep and this results increase in the fertility of the soil.
Hence,relief or slope role be important in the formation of soils in India.
Climate is the most important factor of all the factors of formation of soil in India,due to the following reasons.
Rainfall and temperature
Amount of rainfall and temperature for a soil formation is largely contributed by the climate.
The presence of micro-organisms is directly controlled by the climatic conditions of a region.
If the climate is rainy,the upper soil is degraded as a result in the occurrence of soil erosion.
In arid and semi-arid regions (desert regions), evaporation always exceeds precipitation.This results in very little vegetation and the soils badly lacks in humus content.
In cold climates of Himalayan region, the process of plant decay is very low, which makes the formation of soil to grow acidic in nature.
Thus these are the major reasons to prove that climate plays a very crucial role in the formation of soil.
Natural Vegetation is formed by the combined effects of climate and relief. The soil formed has a great impact from the growth of vegetation because the remains of plants which are decayed over a large duration adds much humus which helps to increase the fertility of the soil.As a result,the forest regions of the country contain the best soils in India.
Hence, natural vegetation plays a very crucial role in the formation of soils in India.
What are the Crops grown by Different Soils in India ?
How different types of soils are distributed in India?
Disribution of different Soils in India
Alluvial soils are very fertile soils. The important food crops in India are grown in Alluvial soil.With intense cultivation, the areas of this soil is densely populated.
Alluvial soils are usually deficit in nitrogen and humus, due to this deficiency fertilizers needed to be added to soil.
Geological Divisions of Alluvial Soil
Alluvial Soils are further classified into Khadar and Bhangar
Khadar is composed of new alluvium and forms the flood plains along the river banks.
Bhangar is older alluvium along the river beds forming terraces higher than the flood plain (about 30 meters above the flood level)
Terai is an ill-drained, damp (marshy) and thickly forested narrow tract (15 to 30 km wide) to the south of Bhabar running parallel to it.
The underground streams of the Bhabar end
Alluvial soil are further
Coastal Alluvium Soil
Alluviums of the Peninsular coastal Alluvium trip are darker in colour than the alluvium of the northern plains because the rivers of the peninsula flow over the Deccan plateau composed of basalt and over black soil are only to deposit it in coastal areas.
Maharashtra has no alluvial soils but coastal alluvium is present in that state.
Distribution of Alluvial Soil
Alluvial soil are distributed in the states of Punjab,Uttar Pradesh,Bihar and west Bengal which are drained by Indus,Ganges and Brahmaputra river systems.Besides, these are also present in coastal regions of Orissa, Andhra Pradesh and Tamil Nadu which are the delta regions of Godavari, Krishna and Cauvery rivers.
- Wheat is the 2nd most food crop of India.
- Wheat needs 12 to 15 inches of water to produce a good crop.
- It grows best when temperatures are warm, from 21 to 24C,but not too hot.
- Wheat also needs a lot of sunshine,especially when the grains are filling.
- Plain land or gentle slope is ideal for wheat cultivation.
- It is a crop which is grown in winter.
- U.P is the largest producer of wheat followed by Rajasthan,Haryana
- pH of wheat is 6.0 – 6.8
- type of loamy,clay
So, wheat grows well in black soil.
- Maize is popularly known as corn worldwide.
- Maize is known as queen of cereals because it has highest genetic yield potential among the cereals
- In India maize or corn is the third most important food cash crops after wheat & rice.
- Maize is grown throughout the year in all states of the country.
- Maize is largely cultivated crop in north India.
- Major maize or corn growing states are Mp followed by u.p , Rajasthan, Bihar and Karnataka and Andhra Pradesh states are the major producers of maize in south India.
- Local names of Maize in India : Maka (Hindi, Marathi, Oriya),Bhutta (Bengali), Makai (Gujarati), Makka’y (Kashmiri), Musikinu jola (Kannada), chollam (Malayalam), makai chollam (Tamil Nadu), Mokka Jonalu (Andhra Pradesh)
- Maize is a rain-fed kharif crop which is sown just before the monsoon starts.
- Maize grown well under temperatures varying from 22c to 30c, but can tolerate upto 35c
- Maize requires 50cm to 90cm of rainfall.
- Maize can be successfully cultivated in a variety of soils ranging from clay loam to sandy loams to black cotton soil.
- For better yield of maize,one should consider soils with good organic matter content having high water holding capacity. With drained soils with pH of 5.5 to 7.0 are preferred for maize farming,
- Soil test is recommended to find out deficiency of any nutrient values in the soil, any deficiency can be covered by adding good organic matter or compost at the time of land preparation.
- Cotton is the most important fiber crop not only in India but of the entire world.
- Cotton is a water thirsty crop and 6% of the water for irrigation in India is used for cotton cultivation.
- It provides basic raw material for cotton textile industry.
- Gujarat, Maharashtra, Punjab, Uttar Pradesh, Madhya Pradesh, TN, AP are the principle cotton producing states in India.
- Types of Cotton:
Long Staple Cotton – length varies from 24 to 27mm
Medium Staple Cotton – length varies from 20 to 24mm
Small Staple Cotton – length varies from less than 20mm long
- Hot and moist climate is ideal for cotton farming.
- Seventy percent cotton is rain-fed. Clear Sunshine and proper moisture level during boll information is required.
- Temperature – 25c is ideal for cotton cultivation.
- Rainfall – 150cm to 200cm rainfall is essential for cotton farming.Moisture in the wind is necessary.
- Soil – Irrigated cotton should be grown on medium black to black deep soil having pH range between 6 to 8.
- Saline soil is not suitable for cotton cultivation.
- Soil should have proper drainage.
- The depth of the soil should be less than 20 to 25cm.
- Frost is effected by cotton crop.
- Millet have been cultivated in India since pre-historic times.
- Millet’s are generally grown as mixed crops in regions of low rainfall, the other crop grown with them being one of the legumes.
- Most of the millets grown in our country are of short duration, taking, three to four months from sowing to harvesting. Some of the indian are Sorghum, pearl ,millet and finger millet.
- India is one of the leading countries in the world the production of sorghum. The area under this millet is 42.6 million acres,and the production of the grain is estimated lit about 7.4 million tonnes.
- It is chiefly cultivated in Uttar Pradesh, Punjab, Madhya Pradesh, Chhattisgarh, Andhra Pradesh, Maharashtra and Rajasthan.
- The plants are tall coarse annuals, growing to a height of from 90cm to 4.5 in, in nil- florescence is a dense head or panicle.
- The grains are small, white, pinkish in color.
- They can be easily grown in less irrigated and arid regions.
- Sugarcane is one of the main cash crops of India.
- From its juice sugar,gur,alcohol etc. are produced. After the extraction of the juice the fibrous mass left behind is used for making paper and sound insulating board.
- Sugar is a troical crop cannot be cultivated in cold regions.
- It requires rainfall of 150cm and temperatures between 20 to 26c.
- Sea breeze – It grows best when the salt breeze from the sea blows over it.
- Soil – Deep slits or fertile loamy soils rich in lime and salts are very suitable.
- Relief – Stagnant water is harmful for sugarcane cultivation.So well drained level land or sloping is suitable.
- India ranks second in the world in sugarcane production. Tn ranks first in India in highest yield per hectare, followed by Karnataka.
- India is the 2nd largest producer of tobacco with 800 million kg.
- Tobacco occupies a meager 0.24% of the country’s total arable land area.
- It is largely grown in semi-arid and rain-fed areas where the cultivation of alternative crops is economically unviable.
- Potato will grow in any well-drained soil, but they dislike soggy soil.
- Because they do all the growing underground, they can expand more easily in loose, loamy soil than in heavy, compacted, clay soil that keeps plants roots from getting the air and water they need.
- The maximum and minimum temperatures are from 30 to 32 and 18 to 20 c respectively.
- Crop rotation is very important in potato farming.
- Drip irrigation helps farmers increasing potato yield.
- Potatoes are slightly acid soil, pH is around 5.0 but will grow in a range from 5.0 to 6.5.
- Common potato scab can be a problem if the soil pH levels are of sweet or alkaline side.
- Tea is the most important beverage of India.
- Tea thrive well in hot and humid climate .
- There is a very close relation between climate, the yield and the quality of tea. The ideal temperature for its growth is 20 to 30c and the temperatures above 35 and below 10c are harmful for the bush.
- It requires 150 -300 cm annual rainfall which should be well distributed throughout the country.
- Tea bush grows well in well drained, deep , friable loams.
- However, virgin forest soils rich in humus and iron content are considered to be the best soils for tea plantations.
- Coffee is the second most important beverage crop of India.
- Coffee requires hot and humid climate with temperature varying between 15 to 28c and rainfall from 150 to 250cm.
- Dry weather is necessary at the time of ripening of the berries.
- Well drained,rich friable loams containing good deal of humus and minerals like iron and calcium are ideal for coffee cultivation.
What is the importance of pH in Soil?
Soil pH affects the soil’s physical,chemical and biological properties and processes, as well as plant growth. the nutrition,growth, and yields of most crops decrease where pH is low and increase as pH rises to an optimum level.
What is pH?
pH is defined as the negative logarithm (base 10) of the activity of hydronium ions (H+) in a solution.
pH value of soils in India
In general, most of the soils in India are most acidic to neutral in nature.
Alluvial Soil pH value is 6.5 to 8.4
Black Soil pH value is 6.5 to 8.4
Red Soil pH value is 5.5 to 7.5
Laterite Soil pH value is 4.5 to 6.5
Forest Soil pH value is 6.0 to 7.0
Mountain soil pH value is 5.0 to 6.5
Arid and Semi Arid Region pH value is 7.6 to 8.4
Peaty or Marshy soil pH value is 4.4 (approximately)
Saline and Alkaline soil pH value is close to 8.5
What is meant by soil acidity?
Soil Acidity is defined as any soil that has a pH of lesser than (<) 7.0 (neutral value of pH).Acidity is due to hydrogen (H+) ion concentrations of the soil.The higher the H+ concentration,the lower the pH.If the taste is sour, then the soil is acidic in nature.
What is meant by Soil neutrality?
Soil neutrality is defined as any soil that has a pH value equal to 7.0
What is meant by soil alkalinity?
Soil Alkalinity is defined as any soil that has a pH of greater than (>) 7.0(neutral value of pH).Alkalinity is due to OH- ion concentrations of the soil.
Generally, the pH value of Alkaline soil is more than 8.5 due to the presence of sodium carbonate in the soil, as when water combines with sodium carbonate, the OH- ions are formed.
Alkaline soils has a poor soil structure and a low infiltration capacity.The presence of sodium carbonate, causes the soil to swell and difficult to clarify/settle.Thus, they are not suitable for agricultural purposes.
If the taste is sweet, then the soil is alkaline in nature.
Usar soils are alkaline in nature.