INITIAL GROWTH AND NUTRIENT CONCENTRATION IN Eucalyptus urophylla x Eucalyptus grandis CLONES UNDER WEED INTERFERENCE

A presen\ue7a de plantas daninhas em plantios de eucalipto, especialmente nos dois primeiros anos, pode acarretar grandes preju\uedzos \ue0 produtividade, pois reduz a efici\ueancia de aproveitamento dos recursos de crescimento pela cultura. Assim, objetivou-se com este trabalho avaliar os efeitos da interfer\ueancia de plantas daninhas sobre o crescimento inicial de dois clones de Eucalyptus urophylla x Eucalyptus grandis e a concentra\ue7\ue3o foliar de nutrientes na cultura e nas plantas daninhas. O experimento foi instalado em esquema fatorial 2 x 5 + 7, sendo dois clones de h\uedbridos de Eucalyptus urophylla x Eucalyptus grandis, identificados como CNB001 e CNB016, em competi\ue7\ue3o com cinco plantas daninhas Urochloa decumbens (capim-braqui\ue1ria), Ipomoea nil (corda-de-viola), Commelina diffusa (trapoeraba), Spermacoce latifolia (erva-quente) e Panicum maximum (capim-coloni\ue3o). Adicionalmente, foram cultivados os dois clones de eucalipto e as cinco plantas daninhas em monocultivo como padr\ue3o de compara\ue7\ue3o, no delineamento inteiramente casualizado, com quatro repeti\ue7\uf5es. Foram avaliados eucalipto atrav\ue9s da altura de plantas, o di\ue2metro do coleto, o n\ufamero de ramos, a \ue1rea foliar, a mat\ue9ria seca e, o teor foliar de nutrientes do eucalipto, bem como o teor de nutrientes nas folhas das plantas daninhas. O clone CNB001 apresentou crescimento inicial superior ao clone CNB016, no entanto, livre da interfer\ueancia de plantas daninhas, verificaram-se teores foliares semelhantes para a maioria dos nutrientes em ambos os gen\uf3tipos. O clone CNB016 mostrou maior sensibilidade \ue0 interfer\ueancia negativa das plantas daninhas que o clone CNB001, sendo seu crescimento inicial mais afetado por Ipomoea nil e a concentra\ue7\ue3o de nutrientes reduzida pelas esp\ue9cies Panicum maximum, Urochloa decumbens e Commelina diffusa. Panicum maximum apresentou maior interfer\ueancia com o clone CNB001, enquanto Ipomoea nil pouco influenciou o crescimento e o teor de nutrientes deste h\uedbrido. As plantas daninhas apresentaram elevada capacidade de extrair nutrientes do solo, mesmo em conviv\ueancia com os clones de Eucalyptus urophylla x Eucalyptus grandis. A interfer\ueancia imposta \ue0 cultura \ue9 dependente da esp\ue9cie infestante e do gen\uf3tipo de eucalipto.The presence of weeds in eucalypt plantations, especially in the first two years, can result in losses of productivity because it reduces the efficiency of growth resource use by the crop. The objective of this study was to evaluate the effects of weed interference in two Eucalyptus urophylla x Eucalyptus grandis clones on initial growth and nutrient foliar concentration in the crop and weeds. The experiment was conducted in a factorial 2 x 5 +7 in which it used two clones of Eucalyptus urophylla x Eucalyptus grandis, identified as CNB001 and CNB016, competing with five weeds Urochloa decumbens , Ipomoea nil , Commelina diffusa , Spermacoce latifolia and Panicum maximum . Also the two eucalypt clones and the five weeds were grown in monoculture as a standard for comparison. It was used a completely randomized design with four replications. The eucalypt initial growth was evaluated by plant height, stem diameter, branches number, leaf area, dry matter and nutrient content in the leaves of eucalyptus. Nutrient concentration in leaves weed also was evaluated. The CNB001 clone showed initial growth upper at the clone CNB016. Free of weed interference both clones presented similar foliar contents for most nutrients. Clone CNB016 was more sensitive to competition with weeds than clone CNB001, being its initial growth most harmed by Ipomoea nil and concentration of nutrients reduced by Panicum maximum, Urochloa decumbens and Commelina diffusa. Panicum maximum showed greater interference with clone CNB001 while Ipomoea nil showed low negative influence in growth and nutrient concentration of crop. The weeds have high ability to extract nutrients from the soil in competition with Eucalyptus urophylla x Eucalyptus grandis clones. The interference imposed on the culture is dependent on weed species and eucalypt genotype