2. • Nitrogen is needed to make protein and
DNA.
• N2 (nitrogen gas) is the most abundant
gas in the atmosphere (78%)
• However, it is not in a usable form for
plants to take up.
• Animals obtain the nitrates (NO3−) from
eating plants.
3. Nitrogen Fixation
• Nitrogen fixation is the process of turning
nitrogen gas into a useable form, nitrate,
NO3-
• Two methods:
a) lightning strikes
b) by certain types of bacteria which live
in the soil.
4. Nitrogen in Agriculture
• Farmers often plant crops like alfalfa and
clover to increase the nitrate, NO3-, levels in
the soil.
• Soil is often aerated (holes are put dug) to
allow oxygen to facilitate the process of
nitrogen fixation.
• Fertilizers also increased the nitrate level.
• Sometimes the extra nitrogen runs off into
the local stream and river
5. Denitrification
• There are some bacteria (called
denitrifying bacteria) which will
break down the nitrate, NO3 -
back to nitrogen gas in a process
called denitrification.
