Soil Science, Soil Profile and Physical Component of Soil.

Concept and relation of soil with the environment

The soil ecology includes issues of the understanding like soil nutrition, the spread of the pathogens like bacteria, fungi, viruses etc. and the impact of the insecticides and the pesticides as well as other chemicals, and the soil porosity. The environmental soil science is the study of the interaction between the humans and the pedosphere and some aspects of the biosphere, hydrosphere, lithosphere and the atmosphere. The Environmental Science addresses both the fundamental and the applied aspects of various fields that include buffers and the surface water quality, septic drain field site assessment and function, land treatment of the wastewater, stormwater, erosion control, soil contamination with the metals and the pesticides, remediation of the contaminate soils, restoration of the wetlands, soil degradation, nutrient management, the movement of the viruses and the bacteria in the soil and the water, bioremediation, application of the molecular biology and the genetic engineering to the development of the soil microbes that can degrade the hazardous pollutants , land use, global warming, acid rain etc.

The soil science includes the physical, life and environmental science in the way that allows us to effectively study the earth's environmental quality. About 99% of the food resources and the other needs from the land demonstrate the importance of the soil in our daily life.

Introduction to the Soil Science

The study of the soil genesis, morphology, properties and the management requiring both the qualitative and the quantitive understandings of the chemical, physical and the biological processes which occur in the soil is known as soil science. Such studies allow us to optimize the use and the preservation of the land for agriculture, forestry, recreation, transportation system, urban development, and many other endeavors.

Soil

The soil is the mixture of the rocks, minerals, decaying matter of the once formed life. It is found in the crust of the earth and is also considered as the skin of the earth where various, plants, animals and micro-organisms settle.

The Duckmans and the Brady defined soil as "a dynamic natural body on the surface of the earth in which plants grow, composed of mineral and organic natural and life forms. "

Raman defined soil as " the uppermost weathered layer of the soil earth crust, it consists of the rocks that have been reduced to the small fragments and have been more or less changed chemically together with the remains of the plants and animals that live on it and in it,"

Velaytham and Bhattacharya defined soil as " Dynamic natural body developed as a result of the pedogenic process through the weathering of the rocks, consisting of mineral and organic constituents possessing definite physical, chemical, mineralogical and biological properties having a variable depth over the surface of the earth and providing a medium for the plant growth."

Thus, soil is the natural dynamic body consisting the fragments of the rock that were weathered by the atmosphere having the physical, chemical. biological and the mineralogical properties with the remains of the plants and the animals that live on it and in it.

Function of the soil

• It supplies mechanical supports, water and nutrient to the plants and the oxygen to the plant root.
• It stores the heat of the sun and supplies it to the root of the plant.
• It is habitat for the very large number of the plants and animals since the origin of life.
• It is an important material for the study of the origin of life.

Components of the Soil

The major components of the soil are

• Mineral matter
• Organic matter
• Soil water
• Soil air

1. Mineral matter

The mineral matter is composed of the small rock fragments and the minerals of various kinds. The mineral matter is of two kinds:

Primary mineral: present in the coarser fraction.

Secondary mineral: Dominants in the fine fraction of the soil (>2mm).

2. Organic matter

They consist of an accumulation of partially decayed and synthesized plant and animal residue. It is the main source of the energy for the soil organisms.

Function of the organic matter:

• supply nutrients to the plants; as it is the storehouse of the nutrients,
• maintenance of the soil structure, bind soil particles,
• increases the activity of the soil.

3. Soil Water

Soil water plays an important role in the soil for the growth of the plant. The soil water makes up the solution containing dissolved salts in it called soil solution. The soil is an important medium for the supply of the nutrient to the plant.

4. Soil Air

Soil air occupies pore not filled with the water. The relative amounts of the air and water in the pore space fluctuate continuously. The soil air contains the higher concentration of the CO₂ than the atmosphere due to the following processes

• Root respiration
• Organism respiration
• Decomposition of the organic matter
• Chemical and mineralogical composition of the Soil.

Soil Profile

The vertical section of the soil extending into the unweathered parent material of the soil components normally moving to the 6 ft and exposing into different horizons is known as soil profile. The vertical section of the soil exposes the presence of the more or less distinctive layers known as profile and the individual distinct layers are known as horizons. No two soil horizons are exactly alike and have distinctive profile characteristics. The uppermost layer of the soil is darker in color than the lower. Due to the accumulation of the organic matter, the coloration of the soil differs as the organic matter contains the decay of the plant roots and other organic residues incorporated into the upper soil layers. The amount of the organic matter gradually decreases with the depth. The higher amount of the organic matter is present on the top of the soil which also supplies the nutrients to the plants.

Physical composition of the Soil

The major physical components of the soil are Inorganic materials or mineral materials, Organic matter, Water, and the Air.

The mineralogical components consist of the different soil textures like sand, silt and clay. The mineralogical soil consists of the four components in the thoroughly mixed condition in the soil. The composition of the four components are

Inorganic material or the mineral material - 45%

Organic material - About 50 %

Water - About 20 to 30 %

Air - About 20- 30 %

The subsoils are lower in organic components, pore space and contain a higher amount of the small pores that are filled much of time with water rather than air.

References:

Keller, E.A. Environmental Geology. Columbus, Ohio: Charles E. Miller Publishing Company, Bell, and Howell Company, 1985.

Mahapatra, G.B. Textbook of Physical Geology. Shahadra,Delhi-110032: CBS Publishers and Distributers Pvt.Ltd., 1992.