• They are called biogeochemical cycles (Nitrogen, phosphorus and carbon cycle)

Nitrogen cycle

Nitrogen Cycle.pdf

Process of transfer of nitrogen in the nitrogen cycle

• There 78% of nitrogen in the atmosphere
• It’s essentially for organisms
  • Preparation of Fats and Proteins in organisms
  • Example: Chlorophyll in plant is made from protein, its there in DNA and RNA (basis of life).
• Atmosphere - Soil - Plants - Animals
• Plants and animals can only take the nitrogen in the form of nitrites and nitrates (nitrogen compounds).
  • Cannot take in the form of actual nitrogen which exists as N$_2$
  • An exception is the leguminous plant, in its root nodules it has a bacteria called rhizobium which has the ability to convert free nitrogen into nitrite and nitrate
    • The only plant which can convert the free nitrogen into nitrite (NO$_2$) and nitrate (NO$_3$)
• Leguminous plants
  • All of the pulses (all lentils and peas)
  • Special plant that can convert the atmospheric nitrogen (free nitrogen) into nitrate and nitrite (nitrogen compounds) through their specialised root system consisting of specialised bacteria called rhizobium present in the root nodules. The rhizobium bacteria converts the free nitrogen into nitrogen compounds
  • Nitrogen fixation: converting the atmospheric oxygen into nitrogen compounds
• Another way in which nitrogen fixation can happen is during lightning. When lightning strikes an enormous amount of heat energy is released, this energy causes the atmospheric nitrogen to convert into nitrogen compounds of nitrates and nitrites by combining with oxygen present in the atmosphere
• Humans and animals consume the plant products and indirectly absorb nitrogen compounds. In a food chain or food web the nitrogen compounds flow from the producers to the consumers and thats how they make nitrogen up the food chain
• Once humans absorb nitrogen, we excrete it

Process of Ammonification

• The nitrogen compounds that are consumed by humans are then digested to ammonia which is later excreted
  • That's how it goes back into the soil

Nitrification:

• Then the ammonia in the soil is converted back into nitrogen compounds through various types of bacteria, for example the pseudomonas bacteria.

Denitrification

• Basically conversion of nitrogen compounds in the soil into free nitrogen
  • This is also through bacteria

Ammonification ——> Nitrification ——> Denitrification ——> Ammonification

Carbon Cycle