EVALUATION OF THE PRODUCTIVITY, CONTENT AND NUTRIENT USE EFFICIENCY IN GENOTYPES OF Eucalyptus spp. IN JEQUITINHONHA VALLEY, MG

<p>The hybridization of eucalyptus species can provide more productive hybrids and with a high efficiency of nutrient absorption and, or, nutrient use, depending on the combined species. In this context, the present work was undertaken in the Jequitinhonha Valley region, Minas Gerais, and its objectives were: to determine the productivity, content and use efficiency of N, P, K, Ca and Mg in interspecific hybrids of <em>Eucalyptus</em> spp. In each plot, the diameters were measured at breast height (DBH) in all the trees, and three trees with diameter similar to the average mean were felled. The volume of the trees was estimated by the Smallian method, using the height, diameter and the bark thickness at the base and at 25, 50, 75 and 100 % of the commercial height. The fresh weight of the wood, bark, leaves and branches was determined in the field, and samples from them were collected for the determination of dry matter. The log samples consisted of collected disks with bark, from the base and at 25, 50, 75 and 100 % of the commercial height. The samples of vegetable tissues were analyzed for: N, P, K, Ca and Mg. The results obtained did not show significant differences for the production of crown biomass between the eucalyptus hybrids of the same age. However, the production of log biomass presented significant differences and the naturally pollinated hybrids of <em>Eucalyptus urophylla</em> were 50.0 % and 69.0 % more productive compared with the hybrids of <em>Eucalyptus urophylla</em> with <em>Eucalyptus grandis</em> and <em>Eucalyptus urophylla</em> with descendants of the crossing of <em>Eucalyptus camaldulensis</em> with <em>Eucalyptus grandis</em>, respectively. Also, these hybrids allocated larger amount of biomass in the log (92.3 %) in relation to the crown (7.7 %), and they were more efficient in the absorption and use of N, P, K, Ca and Mg. The conclusions were that: 1) same aged hybrids of <em>Eucalyptus urophylla</em> from natural or controlled pollinations did not differ in their crown biomass; 2) log biomass was reduced in the hybrids from controlled pollination between <em>Eucalyptus urophylla</em> with <em>Eucalyptus grandis</em> and <em>Eucalyptus urophylla</em> with descendants of the crossing of <em>Eucalyptus camaldulensis</em> with <em>Eucalyptus grandis</em>; 3) hybrids of <em>Eucalyptus urophylla</em> from natural pollination were more productive and more efficient in the absorption and efficiency of use of N, P, K, Ca and Mg and 4) hybrids of <em>Eucalyptus urophylla</em> with descendants of the crossing of <em>Eucalyptus camaldulensis</em> with <em>Eucalyptus grandis</em> are less productive and less efficient in the absorption and use of N, P, K, Ca and Mg.