Young eucalyptus seedlings in general are sensitive to stress factors during early development and establishment. Weed competition is one of the major biotic effects contributing to reductions on the initial growth of eucalyptus plants. This study aimed to evaluate the effects of different densities and distances of Urochloa decumbens seeded and regrowth during the early growth of Eucalyptus urograndis. Two experiments were conducted in an open and semi-controlled area, in a completely randomized design, in factorial arrangement 4 x 2 + 1, being respectively, four densities of weed plants (2.6, 5.2, 7.8 and 10.4 plants m -²), two distances between Eucalyptus and weeds (5 and 15 cm), and a weed-free control. The height and diameter of eucalyptus were evaluated 15 days intervals, and at the end of 90 days after eucalyptus planting (DAP) the leaf area and dry mass were measured. For a density of U. decumbens plants that were seeded at a density of 2.6 plants m -2 , 90 days after Eucalyptus planting (DAP), there was a decrease in the height (20%), stem diameter (10%), leaf area (55%) and dry mass (48%). For the regrowth of U. decumbens at a density of 2.6 plants m -2 at 90 DAP, the height (47%), stem diameter (55%), leaf area (89%) and dry mass (87%) decreased. The results demonstrate that U. decumbens adversely affected the growth of eucalyptus, without statistical differences between distances, and weeds in regrowth affecting Eucalyptus growth more than seeded weeds.

Eucalyptus plants are sensitive to stress factors in the initial growth phase. The plant growth regulator trinexapac-ethyl can provide gains to eucalyptus plants, a phenomenon known as hormesis. Thus, the aim of this work was to evaluate the effect of trinexapac-ethyl on the initial growth of two Eucalyptus urograndis clones (Clone 1 = I-144 and Clone 2 = 1407). The experiment was performed during 90 days after planting (DAP) of eucalyptus, in 100 L pots, with a randomized complete block design. The treatments were arranged in a 2 × 3 factorial scheme, with two eucalyptus clones and three trinexapac-ethyl doses (0, 30 and 60 g i.a. ha -1 ), with four replications. Fortnightly, plants height and stem diameter were evaluated. At 90 DAP, the leaf area and plants dry matter (DM) were evaluated. Clone 1 obtained leaf area and total DM 53% and 58% larger than Clone 2, respectively. The higher dose of trinexapac-ethyl provided mean gains of 30% in stem DM and total DM in Clone 1. For Clone 2, both doses of the product caused mean gains of 70% in stem DM, leaf DM and total DM. In conclusion, trinexapac-ethyl has a positive effect on the initial growth of E. urograndis, Clones I-144 and 1407. Clone I-144 showed higher growth than Clone 1407, regardless trinexapac-ethyl application. However, the Clone 1407 obtained more expressive gains with the application of trinexapac-ethyl, compared to Clone I-144.

In silvopasture system, the coexistence of eucalyptus seedlings with other species may result in growth reduction, especially during eucalyptus early development. Therefore, studies elucidating how forage species affect the eucalyptus growth can provide important information for their rational management aiming to obtain the maximum gain of the system. The aim of this work was to evaluate the effect of increasing densities of Urochloa brizantha cv. Marandu in the early development of Eucalyptus urograndis. An experiment was conducted in 20 L pots, in an open and semi-controlled area, during 90 days after planting of eucalyptus. A completely randomized design with four replications was used, in a 6 9 7 factorial system, meaning six evaluation periods and seven densities of U. brizantha: 0 (control), 22, 33, 44, 67, 89 and 111 plants m-2. Fortnightly, eucalyptus height, stem diameter and chlorophyll fluorescence (F v /F m) were evaluated. At the end of experimental period, the net assimilation rate, stomatal conductance and transpiration rate of eucalyptus plants were determined, in addition to the dry matter of eucalyptus (leaves and stem) and U. brizantha (leaves). In coexistence with 111 plants m-2 , eucalyptus had reduction of 63.9% on total dry matter and 72.7% on leaf area, compared to the control. From the density of 22 plants m-2 , U. brizantha negatively interfere significantly the growth of E. urograndis. Up to 8 plants m-2 there are no reductions greater than 5% in eucalyptus height and stem diameter.

-It was aimed to verify the efficacy and selectivity of herbicides applied alone or in tank mixture for the weed control in peanut crop cv Runner IAC 886. Therefore, it was settled a field experiment, in a randomized block design with four replications. The treatments applied in pre-emergence were: 1-imazapic, 3-imazapic + pendimethalin, and 5-imazapic + trifluralin; the treatments applied in post-emergence were: 2-imazapic, 4-imazapic + pendimethalin, and 10-1 Recebido para publicação em 26/11/2014 e aceito em 24/07/2015.

Eucalyptus plants are sensitive to abiotic stresses in their initial growth, and nutritional deficiency is one of the most recurrent among them. Trinexapac-ethyl, which is a plant growth regulator, can positively affect eucalyptus, a response known as hormesis, possibly providing plants with greater tolerance to stress. The objective of this study was to evaluate the effect of trinexapac-ethyl at two application times, before planting (BP) or after planting (AP), in Eucalyptus urophylla under conditions of nutritional deficiency (NPK). Two experiments (one for each application time) were conducted simultaneously during 81 days after planting of eucalyptus in 15 L pots. The treatments consisted of three doses of trinexapac-ethyl (0, 30, and 60 g a.i.·ha−1) and four variations of nutrient supply: complete solution (NPK) and solutions without nitrogen (−N), without phosphorus (−P), and without potassium (−K). The variables of gas exchange, growth, and dry matter were evaluated. For both application times, trinexapac-ethyl had a positive effect on the root–shoot ratio of plants grown in −N and also positively affected some eucalyptus photosynthetic characteristics. In the AP application, the compound provided gains in height and dry matter, regardless of the nutrient supply. Under phosphorus deficiency, trinexapac-ethyl provided gains in total dry matter (BP) and leaf area (AP).

This study aimed at evaluating the effects of different desiccation periods of Urochloa decumbens on the initial development of Eucalyptus urograndis (clone C-219H). The experiment was conducted in 100 liter concrete boxes, previously filled with Dark-Red Latosol. U. decumbens was sown in all plots, except for the control sample without covering. After 95 days from sowing, the herbicide glyphosate (dose of 1,424 g a.e. ha-1) was sprayed at intervals of 0 (Apply-Plant), 7, 14, 21, 28 and 35 days before eucalyptus planting, plus a control sample without covering, totaling seven treatments. A completely randomized design with six replications was used. Eucalyptus plants were evaluated 30, 60 and 90 days after planting (DAP), when the height of the plants and the diameter of the stem were determined. At the end of the experimental period (90 DAP), the leaf area and the dry matter of leaves and stem were measured. It is possible to conclude that the Apply-Plant modality was harmful to some of the eucalyptus characteristics (E. urograndis - C-219H), while planting the seedlings in periods over 14 days after the desiccation of U. decumbens plants promoted a better development of the culture.

Entre os fatores ambientais, a deficiência hídrica tem efeito em diversosprocessos morfológicos e fisiológicos das plantas, podendo afetar ocrescimento e o desenvolvimento das culturas, refletindo na produtividade.Diante disso, objetivou-se avaliar as características fisiológicas de genótiposde amendoim submetidos à deficiência hídrica. Realizou-se um experimentoem blocos inteiramente casualizados, com os tratamentos dispostos emesquema fatorial 12 × 2, tendo como tratamentos 12 genótipos e duascondições hídricas, em cinco repetições. Para avaliar o efeito do estresse, aos25 dias após a emergência (DAE), as plantas de amendoim permaneceramsob deficiência hídrica por quatro dias, enquanto as testemunhas forammantidas a 70% da capacidade de campo. Aos 29 DAE, foram realizadas asavaliações de fotossíntese, transpiração, teor relativo de água, teor de ceraepicuticular e massa seca das plantas. A taxa fotossintética foi menor paratodos os genótipos sob deficiência hídrica, exceto para a linhagem 870, quedemonstrou maior tolerância à seca. Para a transpiração, as cultivares RunnerIAC 886, IAC OL3, IAC OL4 e as linhagens 573, 599, 870 não foram afetadospela deficiência hídrica. Entre os genótipos, há variação na quantidade deceras epicuticulares sob condições hídricas. Com relação ao comportamentoanatomofisiológico dos genótipos, concluiu-se que as linhagens 573 e 870são altamente tolerantes à deficiência hídrica, as cultivares IAC OL3, IAC OL4,Runner IAC 886 e as linhagens 599 e 967 são moderadamente tolerantes eIAC 503, IAC 505 e IAC Tatu-ST e as linhagens 322 e 506 são mais sensíveisao estresse hídrico durante a fase de florescimento.

Plantas de eucalipto são sensíveis à interferência imposta pela comunidade infestante, principalmente durante o crescimento inicial, período que compreende o primeiro ano após a instalação da cultura. Sendo assim, o presente estudo objetivou avaliar o efeito de densidades crescentes de Commelina benghalensis L. (trapoeraba) sobre o crescimento inicial de plantas de Eucalyptus grandis Hill (ex Maiden) em duas estações do ano (inverno e verão). Foram realizados dois experimentos, um no inverno (durante 90 dias) e outro no verão (durante 120 dias), em área aberta, semicontrolada, em caixas de 70 L. Para ambos os experimentos utilizou-se delineamento em blocos casualizados, com quatro repetições e os tratamentos consistiram de densidades crescentes de trapoeraba: 0 (testemunha), 4, 8, 16, 20, 28, 36, 40, 60 e 80 plantas m-2. Quinze dias após o plantio das mudas de trapoeraba, foi plantada uma muda de eucalipto no centro de cada caixa. Ao final dos períodos experimentais, foram avaliados a altura, o diâmetro, a área foliar e a massa seca da parte aérea do eucalipto. Observou-se que a partir de 4 plantas m-2 já houve interferência negativa no crescimento do eucalipto, com reduções de 38,4% na área foliar e 35% na massa seca, no inverno; e reduções de 52,9% na área foliar e 64,7% na massa seca, no período de verão. Conclui-se que a partir da densidade de 4 plantas m-2 há interferência no crescimento do eucalipto e que, no período de verão, a planta daninha apresenta comportamento competitivo mais agressivo, causando maior interferência nas plantas de eucalipto.