Soil science is an important branch of agriculture science which deals with the studies of different domains like soil physics and chemistry soil fertility and plant nutrition, soil biology and biochemistry, soil survey, genus and classification, soil mineralogical, soil conservation etc.
It is therefore, essential that this valuable natural resources is understood and concept properly for sustained agricultural production in the India.
The study of soil is called soil science.
Soil science deal with soil considered as a natural body and as an important medium for crop growth.
Soil science include :-
1. Soil Geology :- The study of geological material from which the soil is derived and its process of formation.
2. Soil Chemistry :- The study of the chemical components of the soil their interaction with one another and the effect of the chemical environment of the soil.
3. Soil Physics :- Study the effect of physical laws on the evolution of chemical properties and physical properties of the soil.
4. Soil Biology :- The study of the effect of plants, animals and soil microorganisms on the evolution of physical condition and chemical composition of soil.
However, the effect of each one of the above four aspects are so interrelated that it is very difficult to tell the effect of one aspect starts and where it ends.
In fact the study of the soil would reveal to one of this that all this four aspects are every minute, every seconds, are going on simultaneously and that the resultant changes are consequently taking place always in the soil system. So it is essential to study the soil science taking into consideration the above four aspects.
Soil science which deal with the soil as a natural resources in the earth’s surface including soil formation, it’s classification, mapping etc. And properties of soil in relations to the use and management of soil in different basis.
Concepts of soil science
There are two basic concepts of soil science :-
Pedology = Pedon (soil/earth) + logos (discourse/study) = Greek word
Therefore to study the origin, classification and description of soil is called pedology. A pedologist studies the origin of soil, classifies the soil and describes the soil in its natural environment. Therefore it is useful to highway and construction engineers.
Edaphology = Edaphos (soil/ground) + logos (discourse/study) = Greek word
To study the soil from the stand point of higher plants is called edaphology. Edaphology studies the various properties of soil in relation to plant production. The food and fibre production is the main objective of edaphology.
Concept of soil
S »» Stratum/Soul,
O »» Of,
I »» Infinite and
L »» Life.
Soil is defined as the loose surface of the earth which is identified from the original rocks and minerals. It is obtained through the process of weathering.
So in a simply soil may be defined as the accumulation of natural bodies which has been synthesized in profile from a diversified mixture of disintegrated and weathering Minerals and decomposition of organic matter, which cover the surface of the earth and supplies when containing the optimum amount of air and water, mechanical support and substances for plants.
Soil is a natural resource with which the existence of the human beings is closely associated. It is the mantle on the land surface that acts as a medium for plant growth.
Generally, soil is the porous, powdery and unconsolidated outer layer of the erarth’s crust which is formed by weathering of minerals and decomposition of organic substances.
Many words that we use daily have various meaning and may be used in various ways. The word ‘soil’ is no exceptions as a verb it means to ‘make dirty’ as in the case of soiled dishes or clothing.
The term ‘soil’ is derived through old French from the Latin solum which means floor or ground. what a soil scientist calls soil, a geologist may call fragmented rock, an engineer may call earth and an economist may call land.
So there are two approaches in studying soils, one by pedologist which includes the study of origin of the soil, its classification and its description and the other by edophologist which covers the study of soil in relation to growth nutrition and yield of crops.
There are two basic concept of soil that have already involved through two centuries of scientific study the first one considered soil as a natural body, a biochemically weathered and synthesized product of nature and second one considered soil as natural habitat for plant and other living organisms.
Soil is dynamic, three- dimensional (having length, breadth and depth) part of landscape with a three phase (solid, liquid and gaseous) system. Soil is the basis and stratum of life.
From what Soil does form ?
The basic component of soil is mineral, water, air and organic matter. The ratio of these components may change on the different area depending on numbers of factors such as cultivation practice, water supply, drainage system, climate condition etc. This factors may affect the ratio of composition.
Soils are mainly composed of mineral matter and organic matter which contains water and air and other soluble nutrients. Soil is composed with minerals with 45%, air with 25%, water with 25% and organic matter with 5%.
The ratio of water and air in the soil is equal. Composition of soil is the major subject of nutrient management. Soil minerals and organic matter hold the soil nutrients at single place and water is provide nutrients for the plant.
In the soil composition the solid phase is organic matter and minerals and these components are generally stable in nature. Other than that, air and water are the liquid component of soil which are the most complex properties of the soil.
How does Soil forms?
The process of formation of soil is known as pedogenesis. Soil formation is dependent upon the other prevailing process which generally affecting the process of soil formation. Hence, Soils are generally formed by the interaction of different soil forming factors and processes.
Soils are formed from the different types of rocks through the intermediate stage of regolith which is result of weathering.
The different steps are involved sequentally :-
1 The formation of regolith by the breakdown of the bed rock.
2 The addition of organic matter resulting from the decomposition of plant and animal residues and reorganisation of these components by soil forming processes like eluviation and illuviatable to form material of varying depth.
Soil forms by the weathering of rocks. It takes millions of year to form 1 inch of soil in the earth. It is a very slow process.
There are two different phases of soil formation :-
1 Weathering of rocks and minerals and decomposition of rocks and minerals. (destructive phase of soil formation)
2 The development or the formation of soil by some soil forming factors and pedogenic processes. (constructive phase of soil formation)
The first phase of soil formation i.e. weathering of rocks and minerals is considered as the destructive phase and help to change the consolidated rocks and minerals into unconsolidated minerals (parent material) whereas the second phase of soil formation is considered as the constructive process and developed the soil profile.