Importance of Nitrogen | Chemistry | CSEC CXC lessons online – Study Guide

Importance of Nitrogen

All plants need nitrogen for the manufacture of proteins.

However plants cannot make use of the nitrogen in the air.

This nitrogen must first be converted to nitrates before the plant can absorb it. This can be done in two ways:


Nitrogen fixing bacteria present in the root nodule of same plants (legumes) change atmospheric nitrogen to nitrates



Lightning can change atmospheric nitrogen to nitrates


N2 + O2          →     2NO


2NO + O2       →     2NO


2NO + H2O      →   HNO3 + HNO2


Once it is fixed nitrogen it is taken up by plants and changed to protein.

Animals will obtain their protein  from these plants

Upon death of plants and animals all protein is converted to humus

Humus along with excreta is changed by nitrifying bacteria to ammonium compounds.

The ammonium compounds are changed first to nitrite by bacteria

Then nitrite is changed to nitrate by bacteria in a process called nitrification


2NH3 + 302   →       2H+ + H20 + ENERGY

2N0-2 + O2    →       2NO3 + ENERGY


The effect of all of this is to return nitrates to the soil.