Capim-colonião e seus efeitos sobre o crescimento inicial de clones de <i>Eucalyptus </i>× <i>urograndis</i>

Abstract

Esta pesquisa teve o objetivo de avaliar o efeito da convivência de capim-colonião sobre o crescimento inicial de plantas de clones de eucalipto. Foram instalados dois ensaios com mudas de clones de eucalipto e de capim-colonião, que cresceram em parcelas delimitadas lateralmente por paredes de alvenaria preenchidas com terra. O primeiro ensaio obedeceu ao delineamento experimental inteiramente casualizado, com três repetições, e tratamentos em esquema fatorial 5 x 2 (cinco clones de eucalipto, e a ausência ou presença de duas plantas de capim-colonião plantadas a 10 cm da muda de eucalipto). O segundo ensaio foi semelhante ao primeiro, porém, com apenas três clones de eucalipto, cinco repetições, e tratamentos em esquema fatorial 3 x 2 (três clones de eucalipto e a ausência ou presença de capim-colonião). Os clones de eucalipto não afetaram de modo diferenciado o crescimento de capim-colonião, sendo que aqueles que conviveram com a planta daninha não apresentaram diferença no seu desenvolvimento, igualando-os quando sob competição. As características dos clones de eucalipto mais sensíveis à convivência com capim-colonião foram: área foliar, matéria seca de folhas e caule. O clone 3 foi o que se mostrou mais sensível à convivência com capim-colonião e o clone 1 mais tolerante, porém todos os clones estudados tiveram influência negativa da convivência com capim-colonião.

Interference of Urochloa decumbens and Panicum maximum in the initial growth of six clones of Eucalyptus urograndis

“…In addition, Guinea grass was more sensitive than signal grass to coexistence with eucalyptus (Table 7). It was also observed that there was interaction between eucalyptus clones and weed plants, as reported in previous studies (Cruz et al, 2010;Pereira et al, 2013), in which the rate of growth and the architecture of eucalyptus plants were different among the clones. Thus, it is possible to infer that the different heights observed in the clones, such as 31.4 cm for clone 3 and 42.9 cm for clone 4, may have influenced the growth behavior of signal grass and Guinea grass.…”

“…Silva et al (1997) observed that Corymbia citriodora (ex E. citriodora) was more sensitive to competition with Brachiaria brizantha than E. grandis. Different responses for different E. urograndis clones have also been reported (Cruz et al, 2010;Graat et al, 2015).…”

“…are commonly observed on eucalyptus plantations, since eucalyptus cultivation has been expanding into areas previously used for pasture. These weed species have some characteristics that make their control difficult, such as: fast growth, seed dormancy and regrowth, even after herbicide application, making crop establishment and management more difficult (Schreiner, 1988;Toledo et al, 2000Toledo et al, , 2001Cruz et al, 2010). In addition, competition with these weeds may have detrimental effects on several physiological characteristics in eucalyptus, such as photosynthetic rate, stomatal conductance, transpiration rate and water use efficiency (Santos et al, 2015).…”

“…On the other side, the weed interference is one of the most important factors compromising forest productivity in eucalyptus plantations worldwide and has been studied over the past few decades (Sands and Nambiar, 1984;Ellis et al, 1985;Caldwell et al, 1995;Adams et al, 2003;Schaller et al, 2003;Coll et al, 2004;Garau et al, 2008;Cruz et al, 2010;Marques et al, 2015;Bacha et al, 2016). In addition to competing with crops for light, water and nutrients, the weed community also releases allelopathic compounds into the environment, which may interfere in eucalyptus growth (Pitelli, 1987;Brendolan et al, 2000;Toledo et al, 2001;Watt et al, 2003).…”

“…Since the clones have different response to weed interference during early growth (Cruz et al, 2010;Pereira et al, 2013;Graat et al, 2015), evaluate the performance of previously existing and promising clones of E. urograndis, during early growth, and with interference by U. decumbens and P. maximum, may provide information and support for genetic improvement programs. In this way, we aim to evaluate the interference of U. decumbens and P. maximum on the early development of six clones of E. urograndis (E. urophylla x E. grandis) as well as the reciprocal effect.…”