The carbon to nitrogen ratio is called the C:N ratio

The carbon serves as an envirnmental energy source for most microorganisms. They use the carbon to build cells and the N in protien production.

C:N less than 20:1 = high nitrogen content (should not result in immobilization of soil N)
With a high nitrogen content the micro organisms will take N for them selves and convert the remaining organic N into ammonium nitrate (NH4+) in a process called mineralization

Mineralization: organic N (protein) ------> microbial activity------>NH4

Plants absorb the inorganic ammonium nitrate as organic N can not be used by plants.

C:N greater then 20:1 = low N content
The microbes whose activity increases because of the addition of the carbon will not obtain enough nitrogen and will absorb the plant available N from the soil. Causes N deficiency where a high C:N had been added to the soil. The loss of plant available N is called immobilization which is ; NO3 or NH4 ----> microbial activity -----> organic N
Immobilization could tie up the nitrate (NO3) and ammonium (NH4) for months untill the N is released by mineralization of the organic nitrogen

C:N example
400:1 = saw dust and contains 40% carbon.

NH4NO3 is ammonium nitrate and is 33-0-0
CO(NH2)2 is urea and is 46-0-0

Info obtained from Colorado State University