Based on the hypothesis that antecipating of nitrogen application can increase corn grain yield due to more N availability in the initial stages of development, field studies were conducted for three agricultural years (1996/97, 1997/98, and 1998/99) to evaluate different types of management of N application for corn cultivated after winter soil cover crops. This work was developed on a Hapludalf soil, at the experimental area of the Soil Science Departament at the Federal University of Santa Maria (RS, Brazil). A complete randomized block design with split-plots and three replications was used. In the main plots (25 x 5 m), three winter soil cover crops were tested: (a) black oats (Avena strigosa Schieb); (b) a mixture of oats + common vetch (Vicia sativa L.), and (c) oilseed radish (Raphanus sativus). In the sub plots (5 x 5 m), the amount of N (kg ha-1) was applied as broadcast before corn sowing, at corn sowing, and as side-dressing, respectively: (a) 00-00-00, (b) 00-30-90, (c) 30-30-60, (d) 60-30-30, and (d) 90-30-00. N application before corn sowing was done after the dessication of the cover crops, while as topdressing, N was applied when the corn plants presented 4 to 6 uncoiled leaves. Urea was used as a source of N. The results showed that the corn cultivated after oats + common vetch had better performance than when cultivated after black oats and oilseed radish. Nitrogen application before corn sowing is a risky practice, while N application at sowing and as topdressing is a safe recommendation.
nitrogen fertilization; timing of application; crops systems