Nitrogen cycle

• 1. Nitrogen Fixation

  Nitrogen fixing bacteria in the soils can access atmospheric nitrogen in the soil and They convert it into ammonium ions.
• 2. Nitrification

  Nitrifying bacteria convert ammonium ions into nitrite ions and then nitrate ions. Note that there are 2 distinct groups of nitrifying bacteria, one group converts to nitrites, the second to nitrates.
• 3. Denitrification

  A lack of oxygen in the soil will give the competitive advantage to the denitrifying bacteria. They convert nitrate ions back into atmospheric N2
• • legumes (pea family) - have nitrogen fixing bacteria in root tissue
  • Nitrogen fixation occurs in root nodule
  • Plant has evolved biochemistry to convert ammonium ions into proteins - enables the plant to grow in low nitrogen soils (competitive advantage)
• 4. Ammonification is the process of converting organic nitrogen compounds, such as proteins in dead matter, into ammonia (NH3) through the action of decomposers, such as saprotrophs
• mycorrhizae Gives a greater surface area for the plant to absorb nitrates and phosphates - the uptake is enhanced Mycorrhizae receives sugars from plant  Plants associated with mycorrhizae will have an increased yield 
• Denitrification happens in anaerobic conditions
• Assimilation - plant roots take up nitrates to make nitrogen containing molecules such as proteins