Source : Webster's Revised Unabridged Dictionary (1913)

Denitrify \De*ni"tri*fy\, v. t. [Pref. de- + nitrogen + -fy.]
   To deprive of, or free from, nitrogen.

Source : WordNet®

denitrify
     v : remove nitrogen from; "Denitrify the soil" [ant: {nitrify}]
     [also: {denitrified}]