Disponibilidade de micronutrientes em solos e sua correlação com teores foliares em povoamentos jovens de eucalipto

• Autor(a) principal: Sequeira, Cleiton Henrique de
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5551
• topic: Eucalyptus; Micronutrientes; Extratores; Eucalyptus; Micronutrients; Extractors; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Eucalypt is the most widely planted forest species in Brazil, reaching 3.4 million hectares. The utilization of the soil in ongoing rotations, the high yield and the use of highly productive clones lead to the occurrence of deficiency symptoms of micronutrients as Cu, Mn, Fe and Zn. The aims of this work were: 1) to evaluate the availability of Cu, Mn, Fe and Zn for eucalypts in different soils of the State of Minas Gerais; 2) to correlate tree nutritional status with both the capability of nutrient supply and characteristics of soil; 3) to evaluate the nutritional status of different clones. Samples were collected from the 0-20 cm soil layer, and leaf samples from two positions of the tree canopy: a) the upper third (A), or b) the bottom third (B). From each crown portion, completely expanded leaves from proximal (1) and distal (2) positions of the branch were collected. Eucalypt plantations from six regions of the State of Minas Gerais were sampled. The soil samples were analyzed for total organic carbon and clay contents, pH, and Cu. Mn, Fe and Zn contents extracted by Mehlich-1, Mehlich-3 and DTPA. In the leaves were determined Cu, Mn, Fe, and Zn contents. Mehlich-1 and Mehlich-3 were the most effective extractors for all micronutrients analyzed. Copper, Fe and Zn contents by Mehlich-1 and Mehlich-3 extractors showed high correlation to each other, but the value of the correlation coefficient depended on soil textural classes. In general, Mehlich-1 was the best extractor in evaluating the micronutrient availability. Copper, Mn and Zn leaf content showed both significant and positive correlation with soil Cu, Mn and Zn availability by the three extractors, while for Fe leaf content was negatively correlated with the available contents by Mehlich-1 and Mehlich-3 extractors. No significant correlation was observed between nutrients in the leaves and in the soil when DTPA was used as extractor. The best correlation between Cu, Zn, and Fe, in the soil, with these nutrients in the plant was obtained using leaves from the position B1; for Mn, the best correlation was for leaves from A1 position. Soil total organic carbon and clay contents and pH, along with soil nutrient content, improved significantly the power of the regression models in estimating the respective nutrient content in the leaf. In the multiple regression models the foliar Cu and Fe contents correlated in a positive way with both organic matter and clay contents. Foliar Mn content correlated negatively with both organic matter contents and pH soil. Considering soil properties improved the predicting capacity of the regressions especially for Mehlich-3 and DTPA extractors. No difference in leaf micronutrient content was detected among clones of Eucalyptus urophylla, Eucalyptus grandis, Eucalyptus camaldulensis, hybrids of Eucalyptus urophylla x Eucalyptus grandis, and hybrids of Eucalyptus camaldulensis x Eucalyptus urophylla, and a general model for Eucalyptus was accepted to estimate foliar micronutrient content from soil micronutrient availability. Our results indicated the importance of considering soil properties to estimate eucalypt foliar micronutrient content.