1) Change state 2) Remove nitrogen from 3) Turn 
• (v. t.) To deprive of, or free from, nitrogen.
To remove nitrogen from any material or chemical compound. ... (05 Mar 2000) ... 
De·ni'tri·fy transitive verb [ Prefix de- + nitr ogen + -fy .] To deprive of, or free from, nitrogen. 
Type: Term Pronunciation: dē-nī′tri-fī Definitions: 1. To remove nitrogen from any material or chemical compound.
[v] - remove nitrogen from
verb remove nitrogen from; `Denitrify the soil`
to remove nitrogen or nitrogen compounds from. · to reduce (nitrates) to nitrites, ammonia, and free nitrogen, as in soil by microorganisms.