A field experiment was carried out in a TE (Terra Roxa Estruturada) in order to evaluate the effects of urea associated or not with anitrification inhibitor on the soil N-NH4/N-NO3 ratio and on the wheat crop. Urea was applied at the rates corresponding to 0, 30, and 60 kg/ ha the nitrification inhibitor at the rates of 0; 0.75 and 1.50 kg/ha of nitrapyrin. Contents of soil N-NH4 and soil N-NO3 were determined 30 and 60 days after sowing. At harvest, grain yield was computed and grain nitrogen contents were determined for each treatment. It was observed that urea, without nitrification inhibitor, decreased the soil N-NH4/N-NO3 ratio. Association of urea with nitrapyrin reached this ratio until 30 days after the fertilizer application. Wheat did not respond to the association of urea with nitrapyrin. There was no effect of treatments on grain nitrogen content.