Nitrification= it is the conversion of ammonia  into nitrites then into nitrates by nitrifying bacteria. 
dentrification=it is the conversion of nitrites and nitrates into free nitrogen.
1)Nitrification is the process in which atmospheric nitrogen when convt in ammonia is further convt into nitrites and these are furthe oxidised to nitrates.2)The  bacteria involved in nitrifiction are called nitifying bacteria.3)They are chemoheterotrophs and are benefited by utilising energy releasd in  oxidation which is used in Nitrosomonas , Nitrosococcus,Nitrobacter.

Denitrification is just the reverse of this proces .They covnvert nitrate and ammonia into atmospheric nitofen  .2)such bacteria are called denitifying bacteria.3)Such bacteria acts very well in soil with more water an less oxygen and there are high level off thecarbohydrate .Eg Thiobacillus denitrificans , and Micrococcus denitrificans .