Soil Science

Introduction to Soil science

soil science research

Soil Science is that types of Agricultural science which deals with the study of soil as a natural Body or resources on the surface of Earth. OR,

Generally, the study of soil and its characteristics and properties is known as Soil Science.

Soil = There are many definition of Soil according to different – different Scientist. such as:

  • according to Vasily Vasilyevich Dokuchaiev (1846-1903): soil is a debris covering the Rocks and a natural body that is composed of mineral and organic constituents, having a definite component proportion and have a distinct nature.
  • according to  Hans Jenny (1904-1972): Soil is a naturally made body which is formed due to influence of climate (temperature, sunlight, wind and other natural phenomena) and living organisms acting on Regolith or Parent materials(such as-Rocks and minerals) over a period of time.
  • according to Eugene W. Hilgard  (1833-1916): soil is a three-Dimension-ally natural body which is more or less a loose and friable material in which plants, by means of their roots, find a foothold for nourishment as well as habitat for plant growth (to grow crops).

Composition Of Soil-

soil component

Our Earth’s soil is made up of mainly four components, that is-

  1. Minerals = A mineral is a chemical compound that occurs naturally in pure form. Minerals are most commonly presented and found in rocks. and By Weathering of Broad Solid minerals, Formation of True soil occurs. Minerals occupy 45 % volume of Earth.
  2. Organic Matters = An Organic Matters are that kind of Substance or materials that contain large number of Carbon chain. The main Property of Organic matter is that they are mainly Bio degradable materials. so, An organic matter occupy 5 % Volume of Earth.
  3. Water = Basically we know that water is how much expensive or important things for all animals that have life (living things) either they are Plants or humans for their Growth. Water occupy 25 % volume of Earth.
  4. Air = Air is also much expensive for our life like Water.  Air occupy 25 % volume of earth like Water.

Branches of Soil Science-

(1). Pedology = The term PEDOLOGY is derived two Greek words, that is (a). pedon which means soil and (b). logos which means To study. Hence Pedology is the Branch of soil science in which we can deal about soil as a natural body. In Pedology, A pedologist studies and research about the origin of the soil, its classification and the description of soil.

(2).Edaphology = The term EDAPHOLOGY is derived two Greek words, that is (a). edaphos which means soil or ground and (b). logos which means To study. Hence Edaphology is the Branch of soil science in which we can deal about soil and growing of  higher plants over the soil. In Edaphology, edaphlogist do practicals about soil and higher plants growing. and also determine the reasons for variation in the productivity of soils, their fertility power and many other properties either that are chemical or Physical.

Further soil science is categorized into six sub division-

  1. Soil fertility = Soil fertility is one of the main branch of soil science in which we can deal about the Nutrient supplying properties of soil.
  2. Soil chemistry = Soil chemistry is also a branch of soil science in which we can deal about Chemical constituents, chemical properties and the chemical reactions under the soil.
  3. Soil physics = Soil physics is also a branch of soil science in which we deal with the study about the physical properties of soil.
  4. Soil microbiology = Soil microbiology is a branch of soil science which Deals with the study of micro organisms present inside the soil, its population, classification, its role in transformations and so on.
  5. Soil conservation = This Branch of Soil science is Dealing with the protection of soil against physical loss by erosion or against chemical deterioration i.e excessive loss of nutrients either natural or artificial means.
  6. Soil Pedology = It Deals about the genesis, survey and classification of Soil.

Our Earth

General Characteristics of Earth-

Our Earth
  • Our earth has mainly two types of movement that is Rotation or Revolution.
  • Earth has a powerful magnetic field. This is only one reason that our earth has powerful gravitational force towards its centre (core).
  • There is only one natural satellite of the planet Earth that is moon.
  • The diameter of the Earth at the equator is 12,756 km.
  • Earth has eliptical shaped orbit.
  • Earth has spherical like shape.

Age of Earth-

There are some important points related to determine the Age of Earth:

  • For a Long Time; our scientists have not found any way to Find out the exact age of the Earth directly from rocks of earth by Carbon dating method. the reason of difficulty to determine the exact age of Earth is that the Earth’s oldest rocks have been recycled and destroyed and no any oldest rocks may remain.
  • so, scientists have been found the method to determine the probable age of the Solar System and also calculated the age of the Earth by assuming that the Earth and all the celestial bodies in the Solar System was formed at the same time and so,They are of the same age.
  • The ages of Earth rocks are measured by the decay of long-lived radioactive isotopes of elements. These dating techniques, which are firmly grounded in physics and are known collectively as radiometric dating, are used to measure the last time that the rock being dated was either melted or disturbed sufficiently to rehomogenize its radioactive elements. These ancient rocks have been dated by a number of radiometric dating methods.
  • The age of Earth’s oldest rocks and oldest minerals show that the Earth’s age is at least 4.3 billion years but it is not the exact age of Earth’s formation. The best age for the Earth (4.54 Ga) is based on old mineral grains (zircon) that have been reported from sedimentary rocks in west-central Australia recently.

Theory about origin of Earth-

Many Scientist give their theory of ORIGIN OF EARTH, such as- Nebular Hypothesis; Planetesimal Hypothesis; Russell’s binary star Hypothesis and Big bang theory and so on, And these all theories are discussing Below-

(1). Nebular Hypothesis = Nebular Hypothesis Theory was proposed by Immanuel Kant in 1755 and Further this theory was modified by Pierre Laplace in 1796.

  • According to this theory, The whole solar system either sun or any planet (for example earth) were formed from the Primeval Nebula (dust) clouds that is made from the collection of many dusts and gasses.
  • The First celestial or planetary Nebula was discovered by Charles Messier in 1764 and the name of the first celestial or Planetary nebula is DUMBBELL NEBULA, M27.

(2).Planetesimal Hypothesis = Planetesimal Hypothesis was firstly proposed by Thomas C. Chamberlin and Forrest R. Moulton in about 1905.

  • Planetesimal Hypothesis theory was also known as THE THEORY OF BIPARENTAL ORIGIN OF SOLAR SYSTEM.
  • According to This Hypothesis- when the planetary system is formed, there is a Plotoplanetary Disk exist that is made by nabulae.

(3).Russell’s binary star Hypothesis = Russell’s binary star Hypothesis was first proposed by an American Astronomer H. N. Russell in 1937 to remove Sir James Jeans’s TIDAL HYPOTHESIS.

  • Russell’s binary star Hypothesis helps to solve the Problems of Distance between the Planets and the Sun; Angular momentum and Angular velocity of Various Celestial Body such as- Earth, Jupiter, etc present in Our Solar System.
binary star Hypothesis

(4).Big bang theory = Big bang theory was proposed by the Belgian Catholic Priest GEORGES LEMAITRE in 1927.

  • Big bang theory was comes under modern Hypothesis about earth.
  • This Big bang theory explained about the origin of universe and celestial Body.
  • By Big bang theory,  GEORGES LEMAITRE wants to describe about the age of various celestial body.

Realms of Earth

Realms is just like a Region. and Our Earth has mainly three realms-

  1. Atmosphere = The Gasses Region of Earth comes under Atmosphere.
  2. Lithosphere = The Solid state region of our Earth comes under Lithosphere.
  3. Hydrosphere = The Liquid state region of our Earth comes under Hydrosphere.

Formation of soil

Weathering of Rocks and forming of soil

Soil is a natural body mainly formed by Weathering of Large and Broad Rocks and minerals; Weathering is the process of transformation of solid rocks into parent material or Regolith. and also the disintegration of rocks and minerals with the help of physical (such as wind, temperature) and chemical processes (oxidation and Reduction).

Soil Forming Factors

In the Formation of Soil; There are mainly two consecutive stages are following-

  1. Rocks to Regolith
  2. Regolith to True soil

So, the whole process to form True soil is following-


Factors that affects the Soil Formation process-

There are two Basic factors that affects the soil formation Process, i.e.

(1). Passive soil forming factors- The Passive soil forming factors are those factors which represent the source of soil forming conditions that affects it. It includes –

(a).Parent materials = It is that consolidated materials from which our soil is formed. There are two groups of parent materials exist;

  • Sedentary – It is formed in original Place. The Parent materials differ as widely as a Rock.
  • Transported – The parent materials transported from their place of origin.
CAUSESoil Type
By GravityColluvial
By WaterAlluvial or Marine
By IceGlacial
By WindEolion

(b).Relief = Relief is also known as TOPOGRAPHY – RELIEF denote the configuration of the land surface. The topography refers to the difference in Elevation of land Surface.

(c).Time = Soil Formation process is a very slow process requiring thousands of years to develop the True Soil. The Period taken by a Given True Soil from the stage of weathered Rock up to the stage of maturity is considered as Time. Here Mature soils referred as True Soil.

The Time that nature denotes to the formation of true soils is termed as  Pedologic Time.

(2). Active soil forming factors- The active soil forming factors are those type of factors that supply Energy that acts on the mass for the purpose of soil Formation. It includes –

  • Climate = Basically, Climate is the condition of Atmosphere over a long period of time such as a period of 30 years. Climate affects the Soil Formation Process Directly and Indirectly both.
    The Dominant climates recognized are
    (1). Arid (2).Humid (3).Semi-Arid (4).Sub-Humid (5).Temperate (6).Tropical and Sub-tropical
  • vegetation and Organisms = Organisms include all living animals such as plants, animals, microorganisms and man and vegetation includes all the body part (vegetative part) of Plants.

Soil Forming Processes

  1. Fundamental Process = It Includes mainly Four  process such as Humification, Eluviation, Illuviation, and Horizonation.
  2. Specific Process = It Includes mainly Three  process such as Calcification, De-calcification,and Podzolization.

now discussing all these process of soil formations-

  • Humification – Humification is the process of transformation of  organic matter and minerals present in soil  into humus. This process involving the transformation of various organisms.
  • Eluviation – The term Eluviation means washing out. It is the process of removal of Elements in solution by percolating water from the upper to lower layers of soil.
  • Illuviation – The term Illuviation means Washing in. It is the process of collection of soil materials that is washing out from the upper layer by eluviation process in the lower layer.
  • Horizonation –  Horizonation is the process of differentiation of soil in different layers along the depth of the soil.

There are several types of Soil found in India-

  • Red Soil.
    Brown Hill Soil
  • Alluvial soil.
  • Black cotton Soil.
  • Desert Soil.
  • Mountain Soil.
  • sub-mountain soil.
  • Brown hill Soil.
  • Peaty and Marshy Soil, and so on.

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It is Arpan Priy Das from west champaran, Bihar. Arpan started his blog about agricultural information named as “ECOHILLAGRI.COM ” He started his blog to help many agricultural or other students as well as farmers. so, it is necessary for them to learn about agriculture that is useful for students as well as farmers and that all concepts are present in this blog.

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