ABSTRACT In the intercropping of maize with Megathyrsus maximus, the application of herbicides is a technique that can be used to reduce competition between intercrops. This study aimed to evaluate the effect of different glyphosate doses on suppressing the growth of Megathyrsus maximus cv. BRS Quênia intercropped with maize, as well as in weed control. The randomized block experimental design was used and conducted in the field. The treatments consisted of the application of six glyphosate doses, 0; 48; 96; 240; 480; 960 g acid equivalent [a.e.] ha-1, and a maize treatment without the forage with 960 g acid equivalent [a.e.] ha-1. The dose of 260.87 g a.e. ha-1 provides a 50% response to the forage production variable; therefore, it has the potential to suppress M. maximus cv. BRS Quênia. The presence of forage reduces the density and dry mass of weeds, with the species in the weed community: Ricinus communis, Eleusine indica, Alternanthera tenella, Commelina benghalensis, Conyza sp., and Digitaria horizontalis.

RESUMO No consórcio de milho comMegathyrsus maximus, para reduzir a competição entre as culturas consortes, a aplicação de herbicidas é uma técnica que pode ser utilizada. O objetivo deste estudo foi avaliar o efeito de diferentes doses de glifosato para supressão do crescimento deMegathyrsus maximuscv. BRS Quênia em consórcio com milho, bem como no controle de plantas daninhas. O trabalho foi conduzido a campo, em delineamento experimental de blocos casualizados. Os tratamentos consistiram na aplicação de seis doses de glifosato, 0; 48; 96; 240; 480; 960 g equivalente ácido [e.a.] ha-1 e um tratamento de milho sem a forragem com 960 g equivalente ácido [e.a.] ha-1. A dose de 260,87 g e.a. ha-1 fornece 50% de resposta à variável produção de forragem; portanto, tem potencial para supressão de M. maximuscv. BRS Quênia. A presença da forrageira reduz a densidade e massa seca das plantas daninhas, sendo as principais espécies na comunidade infestante: Ricinus communis, Eleusine indica, Alternanthera tenella, Commelina benghalensis, Conyza sp. e Digitaria horizontalis.

ABSTRACT The intercropping between maize and forage species is an alternative commonly used within farming systems. Competition among crops may be a limiting factor in intercropping, compromising maize and forage yield. Although necessary, the literature does not provide satisfactory answers on the interaction of forage crops launched in the market recently, such as BRS Zuri, intercropped with maize. Therefore, techniques such as the use of herbicide subdoses come in as an option to suppress forage growth, making simultaneous cultivation feasible. Thus, the present study aimed to evaluate the effects of glyphosate herbicide subdoses on the development of Panicum maximum cv. BRS Zuri intercropped with Roundup Ready® (RR) maize and how this interaction reflects on the weed population, forage yield, and biometric and yield variables of maize. The experimental design was randomized blocks with treatments consisting of six subdoses of glyphosate herbicide (0, 48, 96, 240, 480, and 960 g acid equivalent [a.e.] ha-1) and maize in monoculture with four replications. For the conditions of this study, the dose of 480 g a.e. ha-1 of glyphosate may be an alternative since there was weed suppression and adequate forage development. Maize yield was not affected by the presence of forage.

RESUMO O consórcio entre milho e espécies forrageiras é uma alternativa comumente utilizada dentro dos sistemas agropecuários. A competição entre as culturas pode ser um fator limitante no consórcio, comprometendo a produção do milho e forragem. Embora necessário, a interação de forrageiras lançadas no mercado nos últimos anos, como a BRS Zuri consorciada com a cultura do milho, não fornece respostas satisfatórias na literatura. Por isso, técnicas como a utilização de subdoses de herbicida entra com uma opção a fim de suprimir o crescimento da forrageira, viabilizando o cultivo simultâneo. Assim, objetivou-se no presente estudo avaliar os efeitos de subdoses do herbicida glyphosate sobre o desenvolvimento de Panicum maximum cv. BRS Zuri consorciado com milho RR (Roundup Ready®) e como essa interação reflete na população de plantas daninhas, no rendimento da forrageira e nas variáveis biométricas e produtivas do milho. O delineamento foi em blocos casualizados, cujos tratamentos consistiram em seis subdoses do herbicida glyphosate (0, 48, 96, 240, 480 e 960 g equivalente ácido [e.a.] ha-1), além do milho em monocultivo com quatro repetições. Para as condições do presente estudo, a dose de 480 g e.a. ha-1 de glyphosate pode ser uma alternativa, visto que houve a supressão de plantas daninhas e um adequado desenvolvimento da forragem. Já o rendimento do milho não foi afetado pela presença da forrageira.

Abstract Brazil is among the countries that most use pesticides in the world. These chemicals cause undesirable changes in ecosystems, particularly the contamination of non-target native forest species through drift. The nuisances caused by pesticides go beyond environmental damage and include public health problems. The objective of this work was to evaluate the effects of glyphosate on leaf gas exchange, photosynthetic pigments and morphoanatomy of seedlings of Eugenia dysenterica. The visual toxicity, physiological and morphoanatomical characteristics of E. dysenterica, when exposed to concentrations of 0, 550, 1110 and 2220 g a.e. ha-1 of glyphosate, were analyzed. The results indicate that the herbicide caused toxicity in the leaves in all treatments. Reductions in photosynthesis (A), stomatal conductance (gs), and transpiration (E) at 47 DAA, were also identified. Glyphosate caused damage to the anatomical structures of E. dysenterica leaves. From the data analyzed it is possible to affirm that plants of E. dysenterica are sensitive to the action of glyphosate. Visible symptoms such as chlorosis and necrosis in the leaf edge are indicators that can be used by rural communities as a warning of the risk of contamination.

Resumo O Brasil está entre os países que mais utiliza agrotóxicos no mundo. Essas substâncias químicas provocam modificações indesejáveis nos ecossistemas, destacando a contaminação de espécies florestais nativas não alvo, através da deriva. Os transtornos causados pelos agrotóxicos extrapolam os danos ambientais, sendo considerados problema de saúde pública. O objetivo deste trabalho foi avaliar os efeitos do glifosato nas trocas gasosas foliares, pigmentos fotossintéticos e morfoanatomia de plântulas de Eugenia dysenterica. Foram analisadas a toxicidade visual, as características fisiológicas e morfoanatômicas de E. dysenterica, expostas a concentrações de 0, 550, 1110 e 2220 g a.e. ha-1 do glifosato. Os resultados apontam que o herbicida causou toxicidade nas folhas em todos os tratamentos. Redução da fotossíntese (A), condutância estomática (gs) e da transpiração (E) aos 47 DAA, também foram identificados. O glifosato causou danos às estruturas anatômicas das folhas de E. dysenterica. Diante dos dados analisados é possível afirmar que plantas de E. dysenterica são sensíveis a ação do glifosato. Sintomas visíveis como clorose e necrose na borda foliar são indicadores que podem ser utilizados pelas comunidades rurais como alerta do risco de contaminação.

The “timed inspiratory effort” (TIE) index, a new predictor of weaning outcome, normalizes the maximal inspiratory pressure with the time required to reach this value up to 60 s, incorporating the time domain into the assessment of inspiratory muscle function. The objective of this study was to determine whether the TIE predicts successful extubation at a similar rate as the T-piece trial with less time required. A non-inferiority randomized controlled trial was performed with ICU subjects eligible for weaning. The participants were allocated to the TIE or the T-piece groups. The primary outcome was successful weaning, and the main secondary outcome was ICU mortality. Eighty participants of each group were included in the final analysis. Time from the start of a successful test to effective extubation was significantly lower in the TIE group than in the T-piece group, 15 (10 to 24) vs 55 (40 to 75) min, P<0.001. In the Kaplan-Meier analysis, no significant differences were found in successful weaning (79.5 vs 82.5%, P=0.268) or survival rate (62.9 vs 53.8%, P=0.210) between the TIE and T-piece groups at the 30th day. In this preliminary study, the TIE index was not inferior to the T-piece trial as a decision-making tool for extubation and allowed a reduction in the decision time.

We examined whether endurance performance and neuromuscular fatigue would be affected by caffeine ingestion during closed- and open-loop exercises. Nine cyclists performed a closed-loop (4,000-m cycling time trial) and an open-loop exercise (work rate fixed at mean power of the closed-loop trial) 60 min after ingesting caffeine (CAF, 5 mg/kg) or placebo (PLA, cellulose). Central and peripheral fatigue was quantified via pre- to post-exercise decrease in quadriceps voluntary activation and potentiated twitch force, respectively. Test sensitivity for detecting caffeine-induced improvements in exercise performance was calculated as the mean change in time divided by the error of measurement. Caffeine ingestion reduced the time of the closed-loop trial (PLA: 375.1±14.5 s vs CAF: 368.2±14.9 s, P=0.024) and increased exercise tolerance during the open-loop trial (PLA: 418.2±99.5 s vs CAF: 552.5±106.5 s, P=0.001), with similar calculated sensitivity indices (1.5, 90%CI: 0.7-2.9 vs 2.8, 90%CI: 1.9-5.1). The reduction in voluntary activation was more pronounced (P=0.019) in open- (-6.8±8.3%) than in closed-loop exercises (-1.9±4.4%), but there was no difference between open- and closed-loop exercises for the potentiated twitch force reduction (-25.6±12.8 vs -26.6±12.0%, P>0.05). Caffeine had no effect on central and peripheral fatigue development in either mode of exercise. In conclusion, caffeine improved endurance performance in both modes of exercise without influence on post-exercise central and peripheral fatigue, with the open-loop exercise imposing a greater challenge to central fatigue tolerance.

Abstract: Background: Ryegrass is considered an important weed in crops in the state of Rio Grande do Sul, Brazil, for being resistant to the herbicide glyphosate. Objective: This study evaluates ryegrass control by applying different spray volumes and doses of clethodim alone or in combination with glyphosate and/or 2,4-D. Methods: Two field experiments were conducted in a 5 x 3 factorial design. In experiment I, factor A consisted of clethodim (96 g a.i. ha-1); clethodim (96 g a.i. ha-1) + glyphosate (1,080 g a.e. ha-1); clethodim (96 g a.i. ha-1) + 2,4-D (1,047 g a.e. ha-1); clethodim (96 g a.i. ha-1) + glyphosate (1,080 g a.e. ha-1) + 2,4-D (1,047 g a.e. ha-1); and control without treatment. Factor B consisted of three spray volumes (40, 80, and 120 L ha-1). In the second experiment, factor A consisted of the same herbicides and their associations aforementioned and factor B consisted of three increasing doses of the herbicide clethodim (96, 192 and 288 g a.i. ha-1). The herbicides were applied at the milky stage of ryegrass grains. Ryegrass control at 10, 20, and 30 days after application (DAA) of herbicides and dry matter were evaluated. Results: Spray volume reduction did not interfere with ryegrass control by clethodim and glyphosate or clethodim, glyphosate, and 2,4-D at 30 DAA, but it did interfere with the application of clethodim alone or associated only with 2,4-D. Doses above 192 g a.i. ha-1 of clethodim alone or in mixture were efficient for ryegrass control. Conclusions: Greater clethodim doses and spray volume increased control of ryegrass at the milky grain stage and decreased the antagonism in the associations with 2,4-D.

The aim of this study was to describe the muscle function, architecture, and composition of long-distance master runners, and verify the association between age and these variables. Additionally, different clusters of runners were compared based on age and training variables. Forty male runners (≥50 years) reported their training routine and had their muscle function evaluated through maximum knee extensor isometric peak torque (PT) assessed with an isokinetic dynamometer. The cross-sectional area (CSA), pennation angle (PA), fascicle length (FL), muscle thickness (MT), and echo intensity (EI) were evaluated through ultrasound (muscle architecture and composition). The participants were 58.7±6.2 years old and had been training for 18.4±10.3 years, 4 sessions/week with 298.8±164.7 min/week of training. The absolute torque was 226.92±63.44 N·m, and the specific torque (PT/CSA) was 7.29±3.78 N·m/cm2. Regarding muscle architecture, the phase angle was 17.34±4°, the fascicle angle 6.78±1.04 cm, muscle thickness 2.93±0.56 cm, and the cross-sectional area 21.24±5.88 cm2. Concerning muscle composition, the master runners showed echo intensity values of 62.05±11.68 AU. The analysis demonstrated a weak and negative association between age and some muscle architecture variables (CSA and MT) and muscle function (PT). No association was verified between age and muscle composition (EI). Age partially explained CSA, MT, and muscle function changes (13, 11, and 14%, respectively). Participants' high level of physical training might have contributed to the low association between these variables and the lack of association with muscle composition.

In cycling, there is a body of evidence that supports that an all-out start strategy is superior to an even-pacing strategy, but it is unknown whether an all-out start strategy is superior to a self-paced strategy. In the present study, we investigated the effects of three different pacing strategies on 4-km cycling time trial performance. After preliminary trials (familiarization trials and a baseline 4-km cycling time trial), in a randomized and counterbalanced order, twelve male cyclists (32.3±7.2 years old, maximum rate of O2 uptake (V̇O2peak) 4.3±0.4 L/min) completed: 1) a self-paced 4-km cycling time trial; 2) an all-out start (∼10 s), followed by maintenance of the average baseline trial power for the first km and self-paced cycling for the remaining trial (all-out+mean); and 3) an all-out start (∼10 s), followed by a power 5% above the average baseline trial power for the first km and self-paced cycling for the remaining trial (all-out+5%mean). Although there was a significant interaction between power and distance (P=0.001) with different power distribution profiles throughout the trial, there was no significant difference (P=0.99) between the three strategies for overall exercise performance (self-paced 379.8±13.9 s, all-out+mean 380.0±16.0 s, and all-out+5%mean 380.2±11.5 s). Oxygen uptake, rating of perceived effort, and heart rate were also similar across the pacing strategies. Different all-out start strategies did not confer additional benefits to performance compared to a self-paced strategy.

The main movements of artistic swimming demand various physical capacities such as flexibility, strength, power, and muscular endurance. The use of ergogenic resources to potentialize performance in this sport, however, is underexplored and deserves investigation. In the present study, we tested whether caffeine ingestion would improve the execution of movements that are essential in a typical figure competition or routines in artistic swimming (i.e., amplitude in the Ariana, height in the Boost and Barracuda, and time maintained in the Stationary Scull techniques). Sixteen experienced female athlete artistic swimmers (17.4±3.2 years of age, 5.6±2.8 years of artistic swimming practice) performed several movements of artistic swimming after having ingested a capsule containing caffeine (5 mg/kg body mass) or cellulose (placebo). Compared to the placebo, caffeine improved latero-lateral amplitude during the Ariana (P=0.035), the height of the Boost and Barracuda (P=0.028 and 0.009), and maintained duration in Stationary Sculling (P=0.012). Bayes factor analysis, however, indicated substantial evidence of a positive effect of caffeine only on the Barracuda and Stationary Scull techniques. These findings indicated that caffeine improved performance during specific artistic swimming movements. Coaches and athletes should consider caffeine ingestion in their supplementation plans.

The present study compared the effects of a footwear designed to enhance energy return (thermoplastic polyurethane, TPU) vs minimalist shoes on running economy (RE) and endurance performance. In this counterbalanced and crossover design study, 11 recreational male runners performed two submaximal constant-speed running tests and two 3-km time-trials with the two shoe models. Oxygen uptake was measured during submaximal constant-speed running tests in order to determine the RE at 12 km/h and oxygen cost of running (CTO2) at individual average speed sustained during the 3-km running time-trials wearing either of the two shoes. Our results revealed that RE was improved (2.4%) with TPU shoes compared with minimalist shoes (P=0.01). However, there was no significant difference for CTO2 (P=0.61) and running performance (P=0.52) comparing the TPU (710±60 s) and the minimalist (718±63 s) shoe models. These novel findings demonstrate that shoes with enhanced mechanical energy return (i.e. TPU) produced a lower energy cost of running at low (i.e., 12 km/h) but not at high speeds (i.e., average speed sustained during the 3-km running time-trial, ∼15 km/h), ultimately resulting in similar running performance compared to the minimalist shoe.

Sedentary time is associated with increased obesity in police officers. Caffeine intake may reduce sedentary time but it has not been extensively investigated. In the present study, the effect of caffeine ingestion on sedentary time was investigated in obese police officers. Fourteen obese police officers ingested either 5 mg/kg of caffeine or cellulose (placebo) for six days. Information on inactivity time, time spent with physical activities, self-reported perception of tiredness, and physical activity disposition was obtained daily during the intervention period. Sedentary and physical activity times were divided into two intraday periods (T1: 08:00 am-02:00 pm and T2: 02:00 pm-08:00 pm). Caffeine intake decreased the sedentary time in both T1 (79.2±2.2%) and T2 (79.1±2.5%), when compared with T2 of the placebo condition (81.1±3.6%, P<0.05). Caffeine intake also increased the time spent on light physical activities in T1 and T2 (17±2 and 18±2%), when compared with T2 of the placebo condition (16±3%, P<0.05). In addition, sedentary time increased and light physical activity time decreased from T1 to T2 in the placebo (P<0.001) but not in the caffeine condition (P=0.81). Caffeine intake had no effect on tiredness (P>0.05), but it increased the self-reported physical activity disposition compared to the placebo condition (4.5±2.7 vs 3.2±2.3 units, P<0.05). Caffeine intake reduced the sedentary time and increased the time spent on light physical activities of obese police officers, which seems to be related to a higher disposition for the practice of physical activity.

RESUMO Objetivou-se: (i) propor um modelo de regressão para a associação entre a injúria em plantas de algodoeiro Roundup Ready (RR) e a deriva dos auxínicos, isolados ou associados ao glyphosate; (ii) avaliar o efeito da adição de glyphosate aos herbicidas auxínicos dicamba e 2,4-D sobre as propriedades físico-químicas das caldas de pulverização e (iii) validar o túnel de vento como ferramenta para realizar a predição de injúria de herbicidas. Foram conduzidos três experimentos, utilizando-se as caldas: glyphosate (0,225 kg e.a. ha-1); dicamba (0,120 kg e.a. ha-1); 2,4-D (0,168 kg e.a. ha-1); glyphosate + dicamba (0,225 + 0,120 kg e.a. ha-1) e glyphosate + 2,4-D (0,225 + 0,168 kg e.a. ha-1). No experimento I foi avaliada a deriva, em túnel de vento às distâncias de 5, 10 e 15 m em relação à ponta de pulverização. No experimento II foi avaliada a injúria em plantas de algodoeiro dispostas nas mesmas distâncias do experimento I. No experimento III estudaram-se as características físico-químicas das caldas utilizadas no experimento I, com avaliações de tensão superficial, pH e densidade. A deriva coletada e a injúria são diretamente proporcionais, seguindo o modelo de regressão linear simples, com aumento do potencial de deriva e injúria aos 5 m de distância da barra de pulverização. A adição de glyphosate aos herbicidas 2,4-D e dicamba reduzem a tensão superficial e o pH das caldas. O túnel de vento além de avaliar o potencial de deriva, apresenta-se como uma alternativa na predição de injúria em plantas de algodoeiro RR.

ABSTRACT The aim was: (i) to propose a regression model for the association between injury in Roundup Ready (RR) cotton plants and drift of auxins, isolated or associated with glyphosate; (ii) to evaluate the effect of adding glyphosate to dicamba and 2,4-D auxinic herbicides on the physicochemical properties of the spray solutions; and (iii) to validate the wind tunnel as a tool to perform herbicide injury prediction. Three experiments were conducted using the following spray solutions: glyphosate (0.225 kg a.e. ha-1); dicamba (0.120 kg a.e. ha-1); 2,4-D (0.168 kg a.e. ha-1); glyphosate + dicamba (0.225 + 0.120 kg a.e. ha -1) and glyphosate + 2,4-D (0.225 + 0.168 kg a.e. ha-1). Experiment I assessed drift in wind tunnel at distances of 5, 10 and 15 m from the nozzle spray drift. Experiment II assessed injury on cotton plants arranged at the same distances as in experiment I. Experiment III studied the physicochemical characteristics of the spray solutions used in experiment I, assessing surface tension, pH and density. The collected drift and injury are directly proportional, following a simple linear regression model, with increased drift and injury potential at 5 m from the sprayer. The addition of glyphosate to 2,4-D and dicamba herbicides reduced surface tension and pH of the spray solutions. The wind tunnel, besides evaluating drift potential, was found to be an alternative for the prediction of injury in RR cotton plants.

Abstract Background: The effect of low rates of glyphosate has been widely studied in several crops. Low nitrogen stress reduces carbohydrate synthesis and we hypothesize that hormesis from glyphosate occurs at low nitrogen availability. Objective: To evaluate the effects of glyphosate hormesis at different levels of nitrogen on the growth and yield of white oat. Methods: A two-factor factorial (2x7) was conducted in field testing at nitrogen levels (50 and 90 kg ha-1) and low rates of glyphosate rates (0 - 180 g a.e. ha-1). The glyphosate was applied at the second node already formed. The growth and yield were evaluated. Results: Plant height was not affected by the nitrogen levels. A low rate of glyphosate induced a plant height increase up of around 10%, but the stimulus was no maintained over in the time. Glyphosate hormesis had a greater effect on dry weight under low nitrogen than under high nitrogen conditions. The glyphosate provided a 43% increase in dry weight at a low nitrogen level when applied at rates consistent with a 4.1% field rate. Glyphosate hormesis increased the yield by approximately 30%, and the yield was higher yield under low nitrogen conditions. Conclusions: The plant height stimulus from low doses of glyphosate was not sustained over time. Glyphosate hormesis stimulus persisted and culminated in an increase in dry weight and grain yield. The hormesis effect on dry weight and yield is more pronounced under lower nitrogen availability.

RESUMO Resíduos no solo, após a aplicação de 2,4-D e dicamba para o controle de plantas daninhas, podem atrasar o estabelecimento e desenvolvimento inicial da soja, mas as chuvas podem reduzir o intervalo necessário entre a aplicação e a semeadura. Volumes de chuva (0; 10; 30; 60; e 90 mm) foram simulados após a aplicação de 2,4-D (300 e 600 g e.a. ha-1) e dicamba (120 e 240 g e.a. ha-1), e os efeitos sobre a soja foram avaliados. A aplicação de 2,4-D não afetou o estabelecimento ou desenvolvimento inicial da soja, independentemente do volume de chuva simulado. No entanto, o residual de dicamba reduziu o estabelecimento da soja para os menores volumes de chuva. A fitotoxicidade foi mais severa para a maior dose de dicamba (75-100 %) e 50-100 % na menor dose. Os maiores volumes de chuva simulados reduziram a fitotoxicidade de dicamba na soja, mas não foram suficientes para reduzir os efeitos deletérios no desenvolvimento inicial da cultura.

ABSTRACT Soil residues following the application of 2,4-D and dicamba for weed control may delay the establishment and initial development of soybean, but rainfall can reduce the interval required between application and sowing. Rainfall volumes (0; 10; 30; 60; and 90 mm) were simulated following the application of 2,4-D (300 and 600 g a.e. ha-1) and dicamba (120 and 240 g a.e. ha-1), and the effects on soybean were evaluated. The application of 2,4-D did not affect the soybean establishment or initial development, regardless of the simulated rainfall volume. However, the dicamba residual reduced the soybean establishment for the lower rainfall volumes. Phytotoxicity was more severe for the highest dicamba rate (75-100 %), being 50-100 % for the lowest rate. The higher volumes of simulated rainfall reduced the phytotoxicity of dicamba in soybean, but were not sufficient to reduce the deleterious effects on the initial development of the crop.

RESUMO O consórcio de espécies de Urochloa com milho é uma alternativa para viabilizar o Sistema Plantio Direto, além de influenciar na comunidade de plantas daninhas. Assim torna-se importante pesquisar subdoses do herbicida glyphosate para o manejo da gramínea no consórcio, para evitar perdas de produção de grãos e viabilizar o consórcio em áreas agrícolas. Objetivou-se avaliar subdoses de glyphosate na supressão de Urochloa brizantha cv. Marandu e Urochloa ruziziensis e o controle de plantas daninhas. Dois ensaios foram conduzidos em campo em delineamento experimental de blocos casualizados, com quatro repetições e oito tratamentos, formados por doses crescentes do herbicida glyphosate (0; 54; 108; 270; 378; 540; 756 e 1.080 g de e.a. ha-1). Em todos os tratamentos foram adicionados 1.200 g de i.a. ha-1 de atrazine. Foram realizadas avaliações de fitointoxicação de plantas de braquiária aos 7, 14, 21 e 28 dias após a aplicação. E aos 80 e 125 dias após a semeadura foram realizadas avaliações de produção de massa seca total, massa seca de folha, massa seca de colmos, relação folha:colmo e altura do dossel, além da densidade e produção de massa seca da comunidade de plantas daninhas. Subdoses de glyphosate abaixo de 238 e de 105 g de e.a. ha-1 possui potencial para serem pesquisadas visando o manejo de U. brizantha cv. Marandu e U. ruziziensis, respectivamente.

ABSTRACT Intercropping of Urochloa species with corn is an alternative to enable the no-tillage system, besides influencing weed community. Therefore, the investigation of underdoses of the herbicide glyphosate to manage grasses in intercropping systems, avoid grain yield losses, and make feasible intercropping in agricultural areas is important. This study aimed to evaluate glyphosate underdoses in the suppression of Urochloa brizantha cv. Marandu and Urochloa ruziziensis and weed control. Two tests were conducted under field conditions in a randomized block design with four replications and eight treatments consisting of increasing glyphosate doses (0, 54, 108, 270, 378, 540, 756, and 1.080 g a.e. ha−1). All treatments received a dose of 1.200 g a.i. ha−1 of atrazine. Evaluations of phytointoxication of brachiaria plants were carried out at 7, 14, 21, and 28 days after application. Moreover, total dry matter, leaf dry matter, stem dry matter, leaf to stem ratio, and canopy height of brachiaria plants and density and dry matter production of weed community were evaluated at 80 and 125 days after sowing. Glyphosate underdoses lower than 238 and 105 g a.e. ha−1 have potential to be investigated aiming at the management of U. brizantha cv. Marandu and U. ruziziensis, respectively.