Air, Water & Soil: Introduction, Pesticides Degradation in the Soil (For CBSE, ICSE, IAS, NET, NRA 2022)

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  • It is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life.
  • Edaphology and Pedology are the two basic branches of soil science.
  • The influence of soils on living things is studied under Edaphology. Whereas ecology focuses on the formation, description (morphology) and classification of soils in their natural environment.
  • Sulphuric acid rain is converted in soil to sulphates.
  • Nitric acid rain produces nitrates in the soil.
  • Pollutants such as toxic metals and radioactive materials can accumulate in the soil being brought by suspended particulate matter from the atmosphere.


Earth՚s body of soil.

Functions of Pedosphere

Soil Pollutants

  • Biodegradation, chemical degradation, and photochemical degradation are the three ways pesticides are degraded in the soil.
  • In the chemical degradation of pesticides an important role is played by water. For e. g. Exposure to sunlight can also degrade some pesticides.
  • During the biodegradation of pesticides an important role is played by microbial activity.

Three Classes of Pesticides


  • These kill insects.
  • Aldrin, DDT, Endrin, Chlordane, etc. are some of the examples.

Chlorinated Hydrocarbons

  • Highly toxic in birds and fishes.
  • For e. g. DDT.


  • More poisonous as compared to other types of insecticides.
  • For e. g. Malathion.


  • Less toxic to mammals.
  • For e. g. Sevin.
  • Usually do not bioaccumulate.


These are derived from plant sources and most of these compounds are toxic to mammals, birds, and aquatic life.

Synthetic Botanicals

  • Low toxicity for mammals, birds, and aquatic life.
  • For e. g. Allethrin.


  • These are used for killing plants.
  • Glyphosate, diclofop, dinoseb, diquat, and paraquat, etc. are some of the examples.

Contact Chemicals

  • These are applied directly to the plants.
  • Also, they cause rapid cell membrane deterioration.
  • For e. g. Paraquat is toxic to humans but does not bioaccumulate.

Systemic Chemicals

  • These are taken up by the roots and foliage of plants.
  • Some of these herbicides are highly toxic to fishes.
  • Bioaccumulation is not there.
  • Alar is one of the best examples.

Soil Sterilant

  • Have low toxicity in animals.
  • Bioaccumulation tendency is not there.
  • Diphenamid is one of the examples which render the soils


  • These kill fungi.
  • These are not very toxic.
  • Neem oil, horticultural oil, and bicarbonates, etc. are some of the examples.
Categories of Fungicides

Protectant Fungicides

  • They protect the plant against infection at the site of application.
  • There is no penetration into the plant.
  • One of the best examples is Captan.

System Fungicides

  • These are absorbed through the plant՚s roots and leaves.
  • For e. g. Sovran prevent disease from developing on parts of the plant away from the site of application.

Soil Types

Types of Soil


Q. what՚s the importance of water in plants?

Answer: Water is useful for plants in many ways:

i) It helps in germination of seeds.

ii) It helps in the photosynthesis process.

iii) It further helps in the transportation of nutrients and minerals from the soil to the plants.

Q. in what way air is useful to us?

Answer: Air is extremely important for the survival of all living organisms.

i) It provides oxygen which is one of the most important things for survival.

ii) It provides us energy and plants get their food from the carbon dioxide present in it.

iii) It contains various other gases being used for a variety of purpose such as nitrogen, carbon dioxide, hydrogen, neon, etc.

Q. What are the three important types of soil resources?

Answer: Three important types of soil resources are:

i) Sand

ii) Silt

iii) Clay

Q. List the various types of soil?

Answer: Various types of soil are:

i) Alluvial

ii) Desert

iii) Black

iv) Mixed red & black

v) Red

vi) Grey & brown

vii) Laterite

viii) Mountain

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