Absorção, transporte e redistribuição de zinco em laranjeiras
teor de Zn dos órgãos das brotações subseqüentes. O Zn, aplicado em cobertura em NEO, movimentou verticalmente, atingindo a profundidade de 20 cm em um ano. A adsorção de Zn foi maior quanto maiores foram a CTC e o pH dos solos, evidenciando a necessidade de se conhecer estes parâmetros para indicar a quantidade de Zn a ser aplicada na adubação. As laranjeiras redistribuíram 21% do Zn acumulado nas partes velhas para as partes novas. Palavras chave: Nutrição vegetal, adubação foliar,
... foliar, fertilidade do solo, radioisótopo. ABSTRACT The knowledge on the methods of applying Zn in orange tree orchards, as well as the absorption, the transport of applied Zn and its redistribution within orange trees, allow a better management of fertilizer with this micronutrient. The Zn deficiency is common in the "São Paulo" State citrus orchards. The objectives were: to evaluate the absorption and the transport of Zn applied in the leaves and in the soil and the redistribution of Zn within the orange trees. Various experiments were carried out in greenhouse, with ´Valência' orange tree budded on 'Swingle' citrumelo. In these studies, 65 Zn labeled fertilizer was used. It was quantified the foliar absorption of Zn from different sources (ZnSO 4 .7H 2 O, ZnCl 2 , Zn-EDTA) and its transport to the organs grown after the application. The contribution of foliar fertilization to the Zn content of the organs developed after the application and the portion of Zn applied on leaves washed by a simulated rain were evaluated. The Zn redistribution within the orange trees was also evaluated. The contributions of Zn applied in the planting hole or on soil surface to the organ grown after the application were quantified. The vertical movement of Zn applied in the surface of "Neossolo quartzarênico" (NEO), contained in pots, was evaluated. The Zn adsorption in eight soil types of the "São Paulo" State was quantified. It was concluded that the foliar application increased the Zn content only in the leaves that received the foliar application, being ZnCl 2 the most efficient source. Less than 5% of the total absorbed Zn was transported to the organs emitted after the fertilization, independently of the applied Zn source. Compared to the ZnCl 2 , the Zn EDTA chelating decreased drastically Zn absorption by the leaves and did not improve its transport to the new organs. Zinc applied to the soil in the transplanting hole or on surface was absorbed by roots and contributed to increase the organs Zn content of the new fluxes. Zinc applied in NEO surface moved vertically, until 20 cm depth, after one year. Higher CEC and pH of soil higher was Zn adsorption, evidencing the need of knowledge on these parameters to determine the amount of Zn to be applied in the soil. Around 21% of Zn accumulated in the old part of orange tree was redistributed to the new fluxes.