ABSTRACT Ryegrass and turnip are weeds that cause high yield losses when infesting barley, thus requiring adequate management. In this context, the aim of this study was to evaluate the selectivity of different herbicide treatments and weed control in the barley crop, cultivar BRS Cauê. Two field experiments were conducted in randomized blocks, with four replications. The treatments used were: pendimethalin (800 g·ha-1), sulfentrazone + diuron (175 + 350 g·ha-1), and imazaquim (150 g·ha-1 of a. e.) applied pre-emergence; and iodosulfuron (3.5 g·ha-1), pyroxsulam (18 g·ha-1), metsulfuron-methyl (3.96 g·ha-1), 2,4-D (670 g·ha-1 of a. e.), clodinafop-propargyl (48 g·ha-1), bentazon + imazamox (600 + 28 g·ha-1), saflufenacil (49 g·ha-1), bentazon (720 g·ha-1), carfentrazone-ethyl (120 g·ha-1), and imazamox (42 g·ha-1) applied post-emergence, with two controls (one weeded and the other infested). The use of the herbicide imazaquim caused high levels of phytotoxicity in barley. Gas exchange was less responsive to herbicide applications in relation to barley phytotoxicity and productivity. Clodinafop-propargil showed the best control of ryegrass, while the herbicides iodosulfuron, pyroxsulam, metsulfurom-methyl, 2,4-D, bentazon + imazamox, saflufenacil, bentazon, carfentrazone-ethyl, and imazaquim showed high efficiency in the control of turnip species. Imazaquim caused reduction of up to 74.7% in barley grain yield. On the other hand, iodosulufuron and piroxsulam allowed the highest grain yields of the barley cultivar, BRS Cauê, by promoting partial control of ryegrass and total control of turnip species, followed by clodinafop-propargyl and metsulfuron-methyl, which controlled ryegrass and turnip, respectively, allowing an increase in yield grain in relation to the infested control.

Resumen El objetivo de este estudio fue evaluar la interferencia y determinar el nivel de daño económico (NDE) de escoba dura infestando diferentes cultivares de soja. Los tratamientos fueron cultivares de soja (NS 6909, NA 5909, DM 5958, Brasmax ELITE, Brasmax LANÇA y SYN 13561) y las densidades de escoba dura (0, 2, 3, 4, 9, 15, 16, 23, 22 y 58; 0, 2, 3, 3, 6, 6, 10, 11, 18 y 47; 0, 3, 4, 7, 8, 10, 11, 13, 15 y 24; 0, 1, 4, 6, 12, 18, 19, 31, 44 y 50; 0, 4, 5, 6, 9, 13, 17, 20, 20 y 47; e 0, 2, 3, 5, 9, 11, 15, 18, 29 y 30 plantas m-2), respectivamente, para cada cultivar. Los cultivares NS 6909, NA 5909 y Brasmax Lança son más competitivos que DM 5958, Brasmax Elite y SYN 13561. Los valores de NDE varían de 0,55 a 0,95 plantas m-2 para los cultivares NS 6909, NA 5909 y Brasmax Lança, que mostraron mejor competitividad. Los valores más bajos de NDE varían de 0,26 a 0,61 plantas m-2 para los cultivares DM 5958, Brasmax Elite y SYN 13561, los cuales mostraron menor competitividad con la maleza.

Abstract This study aimed to assess the interference and threshold level (TL) of Sida rhombifolia, the arrowleaf sida, competing with different soybean cultivars. The treatments comprised different soybean cultivars (NS 6909, NA 5909, DM 5958, Brasmax ELITE, Brasmax LANÇA, and SYN 13561) and densities of arrowleaf sida plants per square meter (m-2) (0, 2, 3, 4, 9, 15, 16, 23, 22, and 58; 0, 2, 3, 3, 6, 6, 10, 11, 18, and 47; 0, 3, 4, 7, 8, 10, 11, 13, 15, and 24; 0, 1, 4, 6, 12, 18, 19, 31, 44, and 50; 0, 4, 5, 6, 9, 13, 17, 20, 20, and 47; 0, 2, 3, 5, 9, 11, 15, 18, 29, and 30, respectively) for each cultivar. Cultivars NS 6909, NA 5909, and Brasmax Lança were more competitive than DM 5958, Brasmax Elite, and SYN 13561. The TL values varied from 0.55 to 0.95 plants m-2 for cultivars NS 6909, NA 5909, and Brasmax Lança, which exhibited greater competitiveness with arrowleaf sida. The lowest values of TL varied from 0.26 to 0.61 plants m-2 for cultivars DM 5958, Brasmax Elite, and SYN 13561, which had less competitiveness with weed.

RESUMEN Entre las malezas que interfieren en el crecimiento y desarrollo del sorgo dulce se destaca el amor seco, especialmente por presentar alta capacidad competitiva por los recursos disponibles en el medio. El objetivo de este estudio es comparar la capacidad competitiva del sorgo dulce (Sorghum bicolor) frente al papunga (Bidens pilosa), en función de la proporción de cultivo y planta. Los experimentos se realizaron en un invernadero en un diseño completamente al azar, con cuatro repeticiones. Los tratamientos se organizaron en series de reemplazo en las proporciones de 100: 0, 75:25, 50:50, 25:75 y 0: 100% (sorgo: maleza) que correspondieron a 20:0, 15:5, 10:10, 5:15 y 0:20 plantas por maceta con volumen de 8 dm3 de sorgo dulce (cultivares BRS 506, BRS 509 o BRS 511) contra B. pilosa. Cincuenta días después de la emergencia, se evaluaron el área foliar de la planta (LA), la masa seca de los brotes (MS), la fotosíntesis (A) y la transpiración (E). La capacidad competitiva se analizó utilizando el método de análisis gráfico, construyendo diagramas basados en la productividad total y relativa. También se determinaron la competitividad, el coeficiente de agrupamiento y la agresividad. Los cultivares de sorgo, en general, fueron menos competitivos en todas las proporciones de B. pilosa. Hubo pequeñas diferencias en la capacidad competitiva entre los cultivares de sorgo; BRS 509 demostró ser ligeramente más competitivo que BRS 506 y BRS 511 frente al B. pilosa a. Sin embargo, es poco probable que esto proporcione una ventaja competitiva para BRS 509 en los campos de producción, por lo que B. pilosa a debe controlarse de manera eficiente al principio del ciclo de cultivo para evitar pérdidas de productividad, independientemente del cultivar de sorgo.

ABSTRACT Among the weeds that interfere with the growth and development of sweet sorghum, beggar ticks stands out, because it has a high competitive capacity for the available resources. This study aims to compare the competitive ability of sweet sorghum (Sorghum bicolor (L.) Moench) against hairy beggarticks (Bidens pilosa L.), as a function of cultivar and plant proportion. Experiments were conducted in a greenhouse in a completely randomized design with four replications and six treatments. Treatments were arranged in replacement series in the proportions of 100:0, 75:25, 50:50, 25:75, and 0:100% (sorghum:weed) equivalent to 20:0, 15:5, 10:10, 5:15 and 0:20 plants per pot with 8 dm3 capacity of sweet sorghum (cultivars ‘BRS 506’, ‘BRS 509’ or ‘BRS 511’) against hairy beggarticks. Fifty days after emergence, plant leaf area (LA), aboveground dry mass (DM), photosynthesis (A), and transpiration rates (E) were measured. Competitive ability was analyzed by using the graphical analysis method and building diagrams based on total and relative productivity. Competitiveness, clustering coefficient, and aggressiveness were also determined. Sorghum cultivars, in general, showed losses independently of the proportion of hairy beggarticks. Statistical analysis showed small differences in competitive ability among sorghum cultivars; ‘BRS 509’ was also demonstrated to be slightly more competitive than ‘BRS 506’ and ‘BRS 511’ against hairy beggarticks. This, however, is unlikely to provide a competitive advantage for ‘BRS 509’ in production fields, and hairy beggarticks should be efficiently controlled early in the crop cycle to avoid productivity losses, independently of the sorghum cultivar.

RESUMO: Este trabalho teve como objetivo determinar o tempo de aquecimento do motor e o número de ensaios que deve ser realizado para aquisição dos parâmetros de desempenho de um motor de ciclo Diesel. Foi utilizado um trator agrícola acoplado via tomada de potência a um dinamômetro de correntes parasitas. Como combustível, foi utilizado biodiesel puro (B100) e determinado o consumo horário por meio da utilização de um fluxômetro. Foram coletados e analisados os dados de torque, potência, consumo horário e específico de combustível, em três tempos de aquecimento do motor (20, 60 e 100 minutos). Para a determinação do número de ensaios, foram realizados 18 ensaios dinamométricos e verificado em quantos ocorre o menor erro experimental, por meio do menor coeficiente de variação. Pode-se observar que, não houve diferença com relação ao tempo de aquecimento para as variáveis analisadas, sendo que o tempo de 20 minutos foi suficiente para iniciar as avaliações de desempenho do motor; e o número de quatro ensaios representando serem suficientes para avaliar o desempenho do motor e reduzir o erro experimental.

ABSTRACT: This research determined the engine warm-up time and the number of tests that must be carried out to obtain the performance parameters of a Diesel cycle engine. To this end, an agricultural tractor coupled to an eddy current dynamometer via a power take-off was used. Pure biodiesel (B100) was used as the fuel, and the hourly consumption was determined by means of a flowmeter. Data regarding torque, power, and hourly and specific fuel consumption was collected and analyzed at three engine warm-up times (20, 60, and 100 min). To determine the number of tests, 18 dynamometric tests were carried out to verify which of those presented the smallest experimental error, through the smallest coefficient of variation. No difference was observed in relation to the warm-up time for the analyzed variables, with a time of 20 min being enough to start the engine performance evaluations. In total, four trials were sufficient to assess engine performance and reduce experimental error.

ABSTRACT The identification of the application stage and correct dose of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide is important so that wheat is not harmed. In view of this, the objective of this study was to evaluate the effect of 2,4-D doses applied at different development stages of wheat crop. The experiment was conducted in a randomized block design, arranged in a 4 × 5 factorial scheme, with four replications. In factor A, the application stages (before tillering, tillering, first node and booting) were allocated and the doses of 2,4-D (0, 349, 698, 1047 and 1396 g.ha–1) were allocated in factor B. The variables evaluated were phytotoxicity at 7, 14, 21, 28 and 35 days after application of the treatments (DAT), photosynthetic activity, CO2 internal concentration, stomatal conductance, efficient water use and carboxylation efficiency. The number of spikes·m–2, spike length and number of full and sterile grains were determined in the preharvest. Thousand grain mass, grain yield and hectoliter weight were determined after harvest. The results demonstrate that the herbicide caused phytotoxicity to wheat, being greater in increasing doses and mainly before tillering, causing grain sterility and decreased productivity. The other yield components did not present difference when increasing the dose and application in different stages as well as the physiological variables. The increase of the 2,4-D doses applied before tillering and in the booting stage caused linear decrease in wheat grain yield.

Resumo O objetivo deste trabalho foi avaliar os efeitos de doses de metsulfurom-metílico, aplicadas em diferentes épocas, sobre as características fisiológicas e produtivas da soja (Glycine max), em dois anos agrícolas, em condições de campo, tendo-se utilizado o pepino (Cucumis sativus) como planta bioindicadora, em casa de vegetação. Os experimentos foram conduzidos em blocos ao acaso, em arranjo fatorial 4x5, com quatro repetições. O fator A foi o tempo de aplicação do herbicida (45, 30, 15 e 0 dias antes da semeadura da soja, DAS), e o fator B foi a dose de metsulfurom-metílico (0, 3,6, 5,4, 7,2 e 9,0 g ha-1 i.a.). Foram avaliadas as seguintes variáveis: fitotoxicidade, trocas gasosas, fluorescência da clorofila a e componentes de rendimento. A maior fitotoxicidade em plantas de soja é observada após o uso da maior dose de metsulfurom-metílico e com semeadura em 0 DAS. A taxa de transporte de elétrons reduz drasticamente com o aumento da dose de metsulfurom-metílico e da proximidade da semeadura, enquanto a extinção não fotoquímica, como mecanismo de defesa, aumenta em plantas de soja expostas ao transporte de herbicida de até 5,4 g ha-1. Os resíduos de metsulfurom-metílico reduzem o peso de mil grãos e a produtividade de soja em função da dose de aplicação e do período de semeadura. Para as plantas de pepino, também foram verificados efeitos negativos nas características fisiológicas. Um intervalo de mais de 45 dias é recomendado para a semeadura da soja após a aplicação de metsulfurom-metílico para dessecação.

Abstract The objective of this work was to evaluate the effects of metsulfuron-methyl rates, applied at different times, on the physiological and productive traits of soybean (Glycine max) in two crop years, in field conditions, using cucumber (Cucumis sativus) as a bioindicator plant, in greenhouse conditions. The experiments were conducted in a randomized complete block, in a 4x5 factorial arrangement, with four replicates. Factor A was the herbicide application time (45, 30, 15, and 0 days before soybean sowing, DBS), and factor B was the metsulfuron-methyl rate (0, 3.6, 5.4, 7.2, and 9.0 g ha-1 a.i.). The following variables were evaluated: phytotoxicity, gas exchange, chlorophyll a fluorescence, and yield components. The highest phytotoxicity in soybean plants is observed after the use of the highest rate of metsulfuron-methyl and with sowing at 0 DBS. The electron transport rate drastically reduces with an increasing metsulfuron-methyl rate and sowing proximity, whereas non-photochemical quenching, acting as a defense mechanism, increases in soybean plants exposed to a herbicide carryover of up to 5.4 g ha-1. Metsulfuron-methyl carryover reduces soybean 1,000-grain weight and productivity as a function of application rate and sowing period. For the cucumber plants, negative effects on physiological traits were also verified. An interval of more than 45 days is recommended for sowing soybean after metsulfuron-methyl application for desiccation.

ABSTRACT The study of weed interference periods and the economic threshold level (ETL) of weeds on crops allows the adoption of management methods and the rationalized use of herbicides. The objective of this study was to determine the periods of interference and to test mathematical models to determine the economic threshold level of ryegrass in the wheat crop. Two experiments were carried out in a randomized block design with four replications. The first experiment was conducted in the 2014/2015 agricultural season. The periods of interference and control of ryegrass were studied in wheat. The periods of interference and/or control were: 0, 10, 20, 30, 40, 50 and 120 days after emergence (DAE). The second experiment was conducted in the 2016/2017 agricultural season. The ETLs were studied, being the treatments composed of wheat cultivars and 12 populations of ryegrass, in competition with the respective cultivars. The results allowed concluding that the management methods of weed ryegrass must be adopted in the period between 11 and 21 days after crop emergence, which is described as a critical period of control of this weed. The wheat grain yield loss competing with ryegrass reached 59% when grown with ryegrass. For ETL, the linear regression model of the rectangular hyperbola adequately estimates grain yield losses in the presence of ryegrass. The cultivar presenting the lowest values of ETL, that is, less capacity to live with the weed, was TBIO Alvorada. The other cultivars presented similar ETL values.

RESUMO As plantas daninhas podem interferir no crescimento e desenvolvimento do feijoeiro, quando não manejadas de forma correta, com destaque para o leiteiro (Euphorbia heterophylla L.). Objetivou-se avaliar a habilidade competitiva de cultivares de feijão preto em convivência com leiteiro. O experimento foi conduzido em casa-de-vegetação, em delineamento inteiramente casualizado, com quatro repetições. Cada tratamento consistiu de uma planta de feijão das cultivares BRS Campeiro, IPR Uirapuru ou SCS Predileto, convivendo com 0, 1, 2, 3, 4 ou 5 plantas de leiteiro, correspondendo a populações de 0 plantas m-2, 22 plantas m-2, 44 plantas m-2, 66 plantas m-2, 88 plantas m-2 e 110 plantas m-2. Avaliaram-se o diâmetro de caule, área foliar, teor de clorofila, altura de planta e massa seca da parte aérea, nas plantas de feijão e leiteiro. As cultivares de feijão apresentaram comportamento diferenciado ao conviverem com populações distintas de leiteiro. A cultivar SCS Predileto apresentou maior habilidade competitiva ao leiteiro, em relação à BRS Campeiro e IPR Uirapuru, o que pode ser verificado pela redução na área foliar e massa seca da planta daninha. Em média, em uma densidade de 110 plantas m-2, o leiteiro reduz, aproximadamente, em 32 % a área foliar e em 50 % a massa seca do feijoeiro.

ABSTRACT Weeds can interfere in the growth and development of bean plants if not properly managed, especially the wild poinsettia (Euphorbia heterophylla L.). This study aimed to evaluate the competitive ability of black bean cultivars coexisting with wild poinsettia. The experiment was conducted in a greenhouse, in a completely randomized design, with four replications. Each treatment consisted of one bean plant of the BRS Campeiro, IPR Uirapuru or SCS Predileto cultivars, living with 0, 1, 2, 3, 4 or 5 wild poinsettia plants, corresponding to populations of 0 plants m-2, 22 plants m-2, 44 plants m-2, 66 plants m-2, 88 plants m-2 and 110 plants m-2. Bean and wild poinsettia plants were assessed for stem diameter, leaf area, chlorophyll content, plant height and shoot dry mass. The bean cultivars behaved differently when cultivated with distinct wild poinsettia populations. The SCS Predileto cultivar showed a higher competitive ability against the wild poinsettia than the BRS Campeiro and IPR Uirapuru, what can be verified by the reduction of leaf area and dry mass of the weed. On average, at a density of 110 plants m-2, the wild poinsettia reduces in approximately 32 % the leaf area and 50 % the dry mass of the bean plants.

Resumo: O objetivo deste trabalho foi avaliar a densidade e a composição do banco de sementes de plantas daninhas do solo ao se cultivar feijão, milho e soja no sistema plantio direto (SPD), em rotação com espécies de cobertura de inverno, e no sistema plantio convencional (SPC). O experimento foi instalado em campo, em delineamento de blocos ao acaso, com três repetições. A contagem do banco de sementes foi realizada em amostras de solo (0-10 e 10-20 cm) em quatro pontos de cada unidade experimental, aos 15, 30, 60 e 90 dias de cultivo. As culturas de feijão, milho e soja foram semeadas no SPD com diferentes coberturas vegetais do solo em rotação, bem como no SPC. O SPD proporcionou banco de sementes do solo com maior densidade e abundância das espécies Gnaphalium spicatum e Oxalis corniculata com o cultivo de milho, soja e feijão. A espécie Lolium multiflorum teve menor densidade e menos sementes no banco do solo ao se adotar o SPD. O uso das coberturas de inverno aveia-preta e ervilhaca, em cultivo isolado ou em consórcio, proporcionou menor densidade de espécies de plantas daninhas, em especial de L. multiflorum. O SPD proporciona menor densidade de espécies de plantas daninhas no banco de sementes do solo que o SPC.

Abstract: The objective of this work was to evaluate the density and composition of the soil weed seed bank when bean, corn, and soybean are cultivated in the no-tillage system (NTS) in rotation with winter cover crop species and in the conventional tillage system (CTS). The experiment was installed in a complete randomized block design with three replicates. The evaluation of the seed bank was performed on soil samples (0-10 and 10-20 cm) in four points of each experimental unit, at 15, 30, 60, and 90 days of cultivation. Bean, corn, and soybean crops were sown in the NTS with different soil cover crops in rotation, as well as in the CTS. The NTS provided a more dense and abundant soil seed bank of the species Gnaphalium spicatum and Oxalis corniculata when corn, soybean, and bean were cultivated. The species Lolium multiflorum showed lower density and less seeds in the soil seed bank when the NTS was adopted. The use of the winter cover crops black oat and cow vetch, cultivated individually or in consortium, resulted in a lower density of weed species, especially of L. multiflorum. The NTS provides a lower density of weed species in the soil seed bank than the CTS.

Resumo: O objetivo deste trabalho foi quantificar o efeito do tipo de diesel e da concentração de biodiesel na mistura combustível sobre as emissões de gases por motor agrícola submetido a diferentes cargas. Foram testados dois tipos de diesel: S10, com baixo teor de enxofre; e S500, com alto teor de enxofre; bem como suas misturas com 5, 10, 15, 20, 50 e 100% de biodiesel. O motor, de quatro cilindros, turboalimentado e com 105 cv de potência máxima, foi submetido a oito modos de operação, sob diferentes rotações e torques. O ensaio seguiu a metodologia prevista na norma NBR ISSO 8174-4:2012, tendo-se analisado as emissões de O2, CO2, NO2, NO, CO e de hidrocarbonetos (HC). Somente as emissões de HC foram influenciadas pelo tipo de diesel utilizado. As emissões de NO2 e O2 aumentaram com o aumento da concentração de biodiesel na mistura, enquanto as emissões de CO2, NO, CO e HC diminuíram. A carga aplicada ao motor esteve diretamente relacionada às emissões, exceto para O2. O combustível S10, com 20% de biodiesel, reduz as emissões, em comparação ao diesel comercial (S500), sem perda no desempenho do motor.

Abstract: The objective of this work was to quantify the effect of diesel type and of biodiesel concentrations in the fuel mixture on gas emissions from an agricultural engine subjected to different loads. Two diesel types were tested: S10, with low sulfur content; and S500, with high sulfur content; as well as their mixtures with 5, 10, 15, 20, 50, and 100% biodiesel. The engine, with four cylinders, turbocharged, and with 105-hp maximum power, was subjected to eight operation modes, under different rotations and torques. The assay followed the methodology set out in standard NBR ISO 8174-4:2012, and the emissions of O2, CO2, NO2, NO, CO, and hydrocarbons (HC) were analyzed. Only the HC emissions were affected by the type of diesel used. The NO2 and O2 emissions increased with greater concentration of biodiesel in the mixture, whereas the CO2, NO, CO, and HC emissions reduced. The load applied to the engine was directly related to the emissions, except for O2. The S10 fuel, with 20% biodiesel, reduces emissions, when compared to the commercial diesel (S500), without losing engine performance.

Objetivou-se com o trabalho avaliar a habilidade competitiva relativa de cultivares de arroz na presença de um biótipo de angiquinho (Aeschynomene denticulata) em diferentes proporções substitutivas de plantas na associação. Os experimentos foram instalados no delineamento de blocos casualizados, com quatro repetições. Primeiramente, tanto para o arroz quanto para o angiquinho, determinou-se a população de plantas em que a produção final de massa seca se torna constante (24 plantas vaso–1). Posteriormente instalaram-se dois experimentos para avaliar a competitividade das cultivares de arroz BRS Querência e BRS Sinuelo CL com plantas de angiquinho, ambos conduzidos em série de substituição, nas diferentes combinações da cultura e da planta daninha, variando-se as proporções relativas de plantas vaso–1 (24:0, 18:6, 12:12, 6:18 e 0:24). A análise da competitividade das espécies foi efetuada por meio de diagramas aplicados a experimentos substitutivos e também pelos índices de competitividade relativa. Aos 50 dias após a emergência das espécies efetuou-se a aferição do perfilhamento ou do número de folhas, da estatura, da área foliar e da massa seca da parte aérea das plantas. Ocorreu competição entre as cultivares de arroz e o angiquinho, sendo ambos afetados negativamente, independentemente da proporção de plantas, provocando, em todos os casos, redução das variáveis avaliadas. Foi observado diferenciação da habilidade competitiva entre as cultivares de arroz quando na presença do angiquinho. A cultivar BRS Querência foi mais competitiva que a BRS Sinuelo CL na presença do angiquinho em todas as proporções de plantas e variáveis testadas.

This study evaluated the relative competitive ability of rice cultivars in the presence of a joint-vetch (Aeschynomene denticulata) biotype, at different replacement levels of plants in the association. The experiments were conducted in a randomized complete block design with four replications. First, it was determined the population of plants in which the final dry mass remains constant, both for the rice and for the joint-vetch (24 plants per pot). Later, two experiments were carried out to evaluate the competitiveness of the rice cultivars BRS Querência and BRS Sinuelo CL with joint-vetch plants, both conducted in replacement series, in different crop and weed combinations, varying the relative proportions of plants per pot (24:0, 18:6, 12:12, 6:18 and 0:24). Competitiveness of each species was analyzed by diagrams applied to replacement experiments and by the relative competitiveness indices. Fifty days after the emergence, tillering or number of leaves, height, leaf area and shoot dry mass were determined. Competition occurred between the rice cultivars and the joint-vetch, both were adversely affected, irrespective of the plant proportion. This resulted in reductions in all evaluated variables. Different competitive abilities were observed between rice cultivars in the presence of joint-vetch. The 'BRS Querência' was more competitive than the 'BRS Sinuelo CL' for all plant proportions and variables tested.