In the Cerrado region a proportion of the top dressed N for corn might be applied to the previous cover crop. This could accelerate the decomposition rate and increase overall N availability to corn. Therefore, the objectives of this experiment were: a) to evaluate maize productivity after oil radish and millet grown in winter with and without nitrogen applied and b) to determine the efficiency of recovery of N fertilizer by corn and quantify the losses by volatilization of ammonia of N fertilizers in no-tillage (NT) and conventional tillage (CT). The experimental design was a randomized complete block in strips with four replications. At flowering, the dry matter production and N accumulation of the oil radish were, respectively, 2,274 and 53.0kg ha-1 under NT, and 2,546 and 61.6kg ha-1 under CT. For millet the results obtained were 5,202 and 107.8kg ha-1 under NT, and 5,101 and 104.1kg ha-1 under CT. Until the seeding of the maize under NT, after desiccation by knife rolling the winter crops, 77.3 and 130.7kg N ha-1 were released in the sequences of oil radish - maize and of millet - maize, respectively. Under CT the winter crops were incorporated into the soil before the seeding of the maize. In the growth cycle of corn the losses of N via ammonia volatilization were less than 2.0% of the N applied at pre-seeding (71.3kg N ha-1 in a mixture urea:ammonium sulphate of 4:1) and 14% of the N at the 6-leaf stage (35.7kg N ha-1 of ammonium sulphate), evaluated in NT and CT in the sequence oil radish - corn. Under NT the fertilizer-N-use-efficiency was 57.1 and 42.1% of the N applied in the sequence millet - corn and oil radish-maize, respectively. Under CT these values were 46.8 and 46.3%, respectively. The application of N fertilizer caused a mean yield increase of 2,396kg grain ha-1 in the sequence millet-corn under NT compared to the non-fertilized control. These increase under CT was 895kg grain ha-1 in the sequence oil radish-corn under NT, and 1,166 and 166kg grain ha-1 in the sequences millet-corn and oil radish-corn, respectively.
pre-plant applied N; Zea mays; winter crops residues; N efficiency; 15N tracer; NH3-N volatilization
