Evaluation of the productivity, content and nutrient use efficiency in genotypes of Eucalyptus spp. in Jequitinhonha valley, MG

A hibrida\ue7\ue3o de esp\ue9cies de eucalipto possibilita a obten\ue7\ue3o de h\uedbridos mais produtivos e com alta efici\ueancia de absor\ue7\ue3o e/ou utiliza\ue7\ue3o de nutrientes, dependendo das esp\ue9cies combinadas. Neste contexto, o presente trabalho, conduzido na regi\ue3o do Vale do Jequitinhonha, Minas Gerais, teve por objetivos: determinar a produtividade, o conte\ufado e a efici\ueancia de utiliza\ue7\ue3o de N, P, K, Ca e Mg de h\uedbridos interespec\uedficos de Eucalyptus spp. Para tanto, mediu-se o di\ue2metro \ue0 altura do peito (DAP) de todas as \ue1rvores presentes em cada parcela, e abateram-se tr\ueas \ue1rvores com di\ue2metro correspondente ao da \ue1rvore m\ue9dia. Procedeu-se \ue0 cubagem das \ue1rvores pelo m\ue9todo de Smallian, utilizando a altura, o di\ue2metro e a espessura de casca na base e a 25, 50, 75 e 100 % da altura comercial. O peso de material fresco do lenho, da casca, das folhas e dos galhos foi determinado no campo, e desses componentes se coletaram amostras para determina\ue7\ue3o do peso da mat\ue9ria seca. As amostras do tronco consistiram de discos coletados, com casca, na base e a 25, 50, 75 e 100% da altura comercial. As amostras de tecido vegetal foram analisadas para: N, P, K, Ca e Mg. Os resultados obtidos n\ue3o indicaram diferen\ue7as significativas para a produ\ue7\ue3o de biomassa de copa entre os h\uedbridos de eucalipto em conseq\ufc\ueancia de apresentarem mesma idade. Entretanto, a produ\ue7\ue3o de biomassa de tronco apresentou diferen\ue7as significativas sendo os h\uedbridos de Eucalyptus urophylla S. T. Blake proveniente de poliniza\ue7\ue3o natural mais produtivo em 50 e 69% em compara\ue7\ue3o aos h\uedbridos de Eucalyptus urophylla W. Hill. Ex Maiden com Eucalyptus grandis Dehnh.e de Eucalyptus urophylla com descendentes do cruzamento de Eucalyptus camaldulensis com Eucalyptus grandis respectivamente. Al\ue9m disso, aqueles h\uedbridos foram os que alocaram maior quantidade de biomassa no tronco (92,3%) em rela\ue7\ue3o \ue0 copa (7,7%), e ainda foram os mais eficientes na absor\ue7\ue3o e utiliza\ue7\ue3o de N, P, K, Ca e Mg. Concluiu-se que: 1) h\uedbridos de Eucalyptus urophylla provenientes de poliniza\ue7\ue3o natural ou controlada n\ue3o apresentam diferen\ue7a na produ\ue7\ue3o de biomassa de copa quando avaliados numa mesma idade; 2) a poliniza\ue7\ue3o controlada de Eucalyptus urophylla com Eucalyptus grandis e com descendentes do cruzamento de Eucalyptus camaldulensis com Eucalyptus grandis reduz a produ\ue7\ue3o de biomassa de tronco; 3) h\uedbridos de Eucalyptus urophylla provenientes de poliniza\ue7\ue3o natural s\ue3o mais produtivos e mais eficientes na absor\ue7\ue3o e utiliza\ue7\ue3o de N, P, K, Ca e Mg e 4) h\uedbridos de Eucalyptus urophylla provenientes de descendentes do cruzamento de Eucalyptus camaldulensis com Eucalyptus grandis s\ue3o menos produtivos e menos eficientes na absor\ue7\ue3o e utiliza\ue7\ue3o de N, P, K, Ca e Mg.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 Eucalyptus 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 Eucalyptus urophylla were 50.0 % and 69.0 % more productive compared with the hybrids of Eucalyptus urophylla with Eucalyptus grandis and Eucalyptus urophylla with descendants of the crossing of Eucalyptus camaldulensis with Eucalyptus grandis, 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 Eucalyptus urophylla from natural or controlled pollinations did not differ in their crown biomass; 2) log biomass was reduced in the hybrids from controlled pollination between Eucalyptus urophylla with Eucalyptus grandis and Eucalyptus urophylla with descendants of the crossing of Eucalyptus camaldulensis with Eucalyptus grandis; 3) hybrids of Eucalyptus urophylla 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 Eucalyptus urophylla with descendants of the crossing of Eucalyptus camaldulensis with Eucalyptus grandis are less productive and less efficient in the absorption and use of N, P, K, Ca and Mg