The Collaborative International Dictionary of English v.0.48:

Nitrogenize \Ni"tro*gen*ize\, v. t. [imp. & p. p.
   Nitrogenized; p. pr. & vb. n. Nitrogenizing.] (Chem.)
   To combine, or impregnate, with nitrogen or its compounds.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nitrogenize
    v 1: treat with nitrogen or a nitrogen compound [syn: nitrify,
         nitrogenize, nitrogenise]