Addressing adsorptive characteristics of soils and zinc and manganese supply to citrus
Franz Walter Rieger Hippler, Iolanda Maria Soares Reis, Rodrigo Marcelli Boaretto, José A. Quaggio & Dirceu Mattos-Jr
This work aimed to study the effects of adsorptive characteristics of soils with different clay content (181 and 644 g kg-1) on the supply of Zn and Mn to citrus. Two experiments were conducted in a greenhouse: the first with the soil application of ZnSO4 (0, 1.0 and 5.0 g/plant of Zn), and the second with the application of MnSO4 (0, 0.7 and 3.5 g/plant of Mn) to young sweet oranges trees. Adsorption curves and binding energy of Zn and Mn in the soils by Langmuir and Freundlich isotherms, and nutrient concentration in the leaves of plants were evaluated in both studies. The application of fertilizers in the clayey soil limited the nutrient supply to plants, based on lower levels of Zn and Mn found in the leaves grown after fertilization. Dueto the higher maximum adsorption capacity of the clay soil for Zn and Mn, the supply of these micronutrients for the plants was limited based on the nutrient levels found in leaves grown after fertilization, when compared to those on the sandy loam soil. The crystallinity of the clay fraction showed few influence on the supply of Zn and Mn to the plants, even though the clay content and the free energy of adsorption reaction were determining factors, mainly at low metal concentration in the soil solution.