Black oat/corn succession has been commonly used in the south of Brazil and N fertilization management is important for its success, especially under no-tillage. This study was carried out at the experimental area of the Department of Soil Science, at Federal University of Santa Maria (RS), Brazil, during 1999/2000, using a Hapludalf (sandy loam/clay loam).The objective was to evaluate the possibility to transfer, partially or totally, the amount of N, normally sidedressed to two applications - black oat tillering and before corn.The experiment was arranged in a randomized block design with four blocks and ten treatments of N management.Each treatment was composed by a sequence of N application for black oat and corn: (1) 00-00-00-00, (2) 15-00-30-45, (3) 30-00-30-30, (4) 45-00-30-15, (5) 60-00-30-00, (6) 00-15-30-45, (7) 00-30-30-30, (8) 00-45-30-15, (9) 00-60-30-00 e (10) 00-00-30-60, where the numbers, respectively, mean N applied in kgha-1 at: (a) black oat tillering; (b) before corn seeding; (c) at corn seeding; and (d) corn sidedress at 4 to 6leaf stage.All treatments received 90kgha-1 of N.As the amount of N applied at black oat tillering increased, dry matter yield also increased and, consequently, the mineral N content decreased in the soil, after oat and prior to corn seeding.The decomposition rate of oat straw seems to be more associated to its produced dry matter than to soil N content.Corn yield decreased as N was removed from corn sidedress and applied to black oat sidedress at tillering.N application before corn seeding increased its availability at the beginning of plant growth, but it was found necessary to maintain sidedress N application.
cultural succession; mineral nitrogen; decomposition rate; nitrogen release