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
• why do leguminous plants grow better in soils with low nitrate ion concentrations compared to other types of plant?

  they are able to convert nitrogen to ammonia, so can therefore produce more proteins for growth