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Soil Nitrogen (Components (Inorganic N <2% (Adsorbed inorganic N…

- - - - e.g. milk
      - Not generally large losses but significant
    - - Hay/grain/crops
      - Can be much larger losses
  - - - Low adsorption of NO3- in most soils as adsorption only occurs by electrostatic attraction; most soils have net negative charge which leads to leaching
      - NH4+ may be adsorbed but quickly nitrified to NO3-
    - - Highly spatially variable
      - Losses of up to 100 kg N/ha
      - Losses affected by stocking rate
    - - Soil type - structure and texture
      - Environmental Conditions (rain)
      - Nitrogen inputs (concentration of NO3- in soil)
  - - - Mainly due to application of urea or other ammonium fertilisers which cause high pH
      - Also from urine patches (high urea content)
  - - - Chemical reaction
      - Generally low losses
    - - Mediated by microbes
      - Requires nitrification
        
        NH4+ - NO2- by Nitrosomonas sp.
        
        NO2- to NO3- by Nitrobacter sp. (rapid)
        
        Requires aerobic conditions
      - Anaeraobic process where nitrate is used in placed of O2 for respiration
      - Must be suitable carbon source available - energy
      - Losses usually greater in agricultural soils than forest soils - more N applied to pastures
- - - - N - steam distillation, colorimetric (manual, CFA or FIA)
      - P - colorimetric (manual, CFA or FIA)
      - K - AAS (diluted) or FES (undiluted)
      - Ca - AAS (N2O/C2H2 flame)
      - Mg - AAS
- - - - N content
      - Immediately available N
      - Price
    - - Ammonium Sulphate -
        
        (NH4)2 SO4 -> NH4+ + SO42-
        
        Sulphur also beneficial
        
        21% N, 24% S
      - Ammonium phosphates
        
        21%N
        
        Phosphorus also beneficial
      - Liquid Ammonia
        
        82%N
        
        Volatilises
      - Ammonium nitrate
        
        33% N
        
        Explosive
      - Organic fertilisers
        
        Recycling
        
        <2% N
      - Urea (NH2)2 CO
        
        46% N
        
        Hydrolyses in water to NH4+ and NH3
        
        Increases pH initially ( up to pH 8-9 around granule)
        
        Decreases pH over time due to nitrification
        
        Use strategically (20-30 kg N/ha-application)
  - - - Gives rise to patchiness in pasture
      - Risk of nitrate leaching and loss of fertility