soil fertility

nitrogen

• nitrogen is a critical component of proteins (and enzymes) nucleic acids, and chlorophyll

• plants with N deficiency exhibit chlorosis

  • yellow or light green leaves

  • stunted growth

  • thin, spindly leaves

• plants take up N as;

  • Nitrate (NO3-)

  • Ammonium (NH4+)

  • Dissolved organic N (DON)

rhyzobia

• rhyzobia form a symbiotic relationship with legumes

• nitrogen is fixed by the nitrogen generating enzyme nitrogenase

• ammonia can be used by the plant for its life cycle

• when the plant dies, the ammonia is released into the soil.

haber-bosch process

• reaction of nitrogen and hydrogen with a metal catalyst to create ammonia

• N2 + 3 H2 → 2 NH3

• energy intensive

• price of N is usually in lock-step with energy prices

organic forms of N

• manures

• green manures

• composts

• wood chips

• anything with a lot of carbon

volitilization

• high in soils with a low CEC bc NH4 is not fixed within the clay

• more pronounced at a high pH

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