RESPOSTAS DE CULTIVARES DE SOJA À ADUBAÇÃO NITROGENADA TARDIA EM SOLOS DE CERRADO

Abstract

The aim was to evaluate the effect of late application of different nitrogen levels in different cultivars. The experimental design was a block design with four replications in a factorial 3 x 5 compounds by combining three soybean varieties: Conquest (early season), Pioneer 98C81 (medium cycle) and M-Soy 9350 (late maturity) and five nitrogen rates: zero, 20, 40, 80 and 160 kg ha-1 applied at growth stage R.1 (early flowering), using urea as nitrogen source. The application of 20 and 40 kg N ha-1 provided an increase in the number of pods per plant in all cultivars. Effect on thousand seed weight in cultivar checked only for conquest, with the application of 20 and 40 kg ha-1 N. Yield was reduced with application of 80 and 160 kg N ha-1 and increased with the application of 20 and 40 kg ha-1 N. There was a similar behavior among cultivars for yield components and yield when subjected to nitrogen in a late period. Although it was observed an increase in production around 300 kg ha-1, is still not economically viable application of nitrogen in soybean.