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

Abstract

Foram conduzidos dois experimentos com objetivo de avaliar o crescimento e estado nutricional da muda de citros, em função de diferentes doses de uréia 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-³ de substrato) e dois substratos (Plantmax® e outro obtido da mistura entre bagaço 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 após o transplantio nas plantas cultivadas no substrato BT, enquanto no Plantmax®, não foi atingido. O teor de N no porta-enxerto cultivado no substrato BT aumenta com as doses de UR. Maiores diâmetro e teor de N nas plantas cultivadas no substrato Plantmax® éobservado na dose 2,4 kg m-3. Usando substrato BT com as características descritas neste experimento, seria possível a obtenção do porta-enxerto tangerineira ‘Cleópatra’ apto aenxertia aos 159 dias após o transplantio e da muda de laranjeira ‘Seleta’, enxertada sobre ele, aos 182 dias após a enxertia, sem complementação da adubação nitrogenada com uréia revestida.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 4.0kg m-³of 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 leavescultivated 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-3. Using the substratum BT with the characteristics described in this experiment, it is possible to attain the rootstock ‘Cleópatra’ 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