Substrata fertilized with coated urea and the growth and nutritional state of the young citrus tree/Substratos fertilizados com ureia revestida e o crescimento e estado nutricional da muda de citros

Two experiments were carried out with the objective of evaluating the growth and nutritional state of the young citrus tree in function of different levels of coated urea (UR). In the first experiment, carried out from transplanting (01/2006) up to the budding point (06/2006), five levels of UR were evaluated (0, 0.5, 1. 0, 2.0 and 4.0 kg [m.sup.-3]of substratum) and two substrata (Plantmax® and another obtained from sugar cane bagasse + filter cake - BT). In the second experiment, carried out from budding until the pinch out point (12/2006), five doses of UR in substratum BT were evaluated. The budding point was reached 120 days after the transplanting in the plants cultivated in substratum BT, while in Plantmax® it was not reached. The concentration of N in the rootstock leaves cultivated in substratum BT increases with the doses of UR. Major diameter and N concentration in the plants cultivated in substratum Plantmax® were observed in a level of 2.4 kg [m.sup.-3]. Using the substratum BT with the characteristics described in this experiment, it is possible to attain the rootstock 'Cleopatra' mandarin in the budding point at 159 days after the transplanting and the young 'Seleta' orange tree, budded on it, at 182 days after budding, without nitrogen fertilization supplementation with coated urea. Key words: slow release fertilizers, agro-industrial residues, propagation, Citrus reshni, Citrus sinensis Foram conduzidos dois experimentos com objetivo de avaliar o crescimento e estado nutricional da muda de citros, em funcao de diferentes doses de ureia revestida (UR). No primeiro, conduzido do transplantio (01/2006) ao ponto de enxertia (06/2006), foram avaliadas cinco doses de UR (0, 0,5, 1,0, 2,0 e 4,0 kg [m.sup.-3] de substrato) e dois substratos (Plantmax® e outro obtido da mistura entre bagaco de cana + torta de filtro - BT). No segundo, conduzido do ponto de enxertia ao de desponte (12/2006), foram avaliadas as cinco doses de UR no substrato BT. O ponto de enxertia foi atingido aos 120 dias apos o transplantio nas plantas cultivadas no substrato BT, enquanto no Plantmax®, nao foi atingido. O teor de N no porta-enxerto cultivado no substrato BT aumenta com as doses de UR. Maiores diametro e teor de N nas plantas cultivadas no substrato Plantmax® e observado na dose 2,4 kg [m.sup.-3]. Usando substrato BT com as caracteristicas descritas neste experimento, seria possivel a obtencao do porta-enxerto tangerineira 'Cleopatra' apto a enxertia aos 159 dias a