Renato Adriane Alves Ruas

Controle de Brachiaria decumbens Stapf com adição de ureia à calda do glifosato

The addition of nitrogen sources to herbicide spray solution s has been related to improvements in phytosanitary treatments. This study aimed at evaluating the control of Brachiaria decumbens with urea added to the glyphosate spray solution. Treatments consisted of a combination of glyphosate (0.0 g ha -1 , 360.0 g ha -1 , 720.0 g ha -1 and 1,080.0 g ha -1 of the a.i.) and urea doses (0.0 g L -1 , 7.5 g L -1 , 15.0 g L -1 and 25.0 g L -1 of the spray solution), and a control with no application, in a randomized blocks design, in a 4x4 factorial scheme, with three replications. Applications were carried out with the aid of a CO 2 constant pressure sprayer, equipped with a bar for two flat jet nozzles, operating at the pressure of 300.0 kPa. Densities and coverage percentages of plants leaves, provided by the jet nozzles drops, were evaluated, as well as the instantaneous gas exchanges, at 12 a.m., at 2, 4, 6 and 11 days after application (DAA), by using a portable infrared gas analyzer. Visual evaluations of control percentage were carried out at 7, 14, 21 and 28 DAA. No difference was observed in the density and coverage of leaves, for the different urea concentrations. The addition of urea to the glyphosate spray solution improved the B. decumbens control, regardless the herbicide dose, up to the 25.0 g L -1 spray solution concentration. The gas exchange of B. decumbens was lower after 6 DAA, in treatments with higher concentrations of urea in the herbicide spray solution, resulting in a higher control level for these treatments.

Aplicação do fomesafen via água de irrigação por aspersão no controle de Euphorbia heterophylla

Herbicide application via irrigation water (herbigation) has been increasingly used in Brazil, mainly through center pivot. The aim of this study was to investigate the efficacy of fomesafen rates applied via overhead sprinkler irrigation for the control of Euphorbia heterophylla. A (4 x 3 x 2) + 3 factorial experiment was used consisting of: fomesafen rates (60, 120, 180, and 240 g ha-1), weed development stages (1, 7, and 14 days after emergence - DAE), application methods (spray and herbigation) and checks that did not receive the herbicide (one for each weed development stage). A completely randomized design with four replications was used. The experimental unit was a pot with four liters of soil, where 50 seeds of the weed were sown. The spray consisted of 200 liters ha-1; for herbigation, a volume of 4.72 mm of water was applied with an irrigation simulator. The most susceptible stage of E. heterophylla was at 1 DAE, when herbigation was more efficient than spraying at the rates of 180 and 240 g ha-1. At 7 DAE, spraying was generally more efficient than herbigation, but the level of weed control was inadequate. Fomesafen was not efficient when applied at 14 DAE, regardless of the rate and the application method.

Estimativa de parâmetros técnicos da tecnologia de aplicação do glyphosate no controle de Brachiaria decumbens

Estimate of technical parameters of glyphosate application technology in the control of Brachiaria decumbens The interaction between the volumetric median diameter (VMD), density (DEN) and coverage (COV) provided by spray droplets is scarcely studied and may influence the application of herbicides in general. This study aimed to estimate the technical parameters of the glyphosate application technology in the control of Brachiaria decumbens Stapf. The treatments consisted of the combination of five rotational speeds of a centrifugal sprayer (105, 157, 210, 262, 315 rad s -1 ) with six travel speeds (0.5; 1.0; 1.5; 3.0; 4.5 and 6.0 km h -1 ).The tests were performed in the laboratory, and the sprayer was adapted into a bar equipped with an electric engine and a control unit to control the travel speed. Visual analyses were carried out and percentage of reduction in plant dry biomass was compared with the control without

Aplicações seqüenciais de fomesafen via água de irrigação por aspersão no controle de Bidens pilosa

Foi conduzido um ensaio em casa de vegetacao com o objetivo de avaliar a eficacia da aplicacao sequencial de pequenas doses do fomesafen por via da agua de irrigacao (herbigacao) por aspersao no controle de Bidens pilosa. Os tratamentos foram dispostos no esquema fatorial 4 x 3 x 2 + 3: doses de fomesafen (50, 100, 150 e 200 g ha-1), sequencias de dias apos a emergencia (DAE) de B. pilosa em que foram realizadas as aplicacoes do herbicida (7-14-21, 14-21-28 e 21-28-35 DAE), metodos de aplicacao (pulverizacao e herbigacao), mais tres testemunhas sem herbicida (uma para cada idade da planta daninha). As tres idades de B. pilosa foram conseguidas com a semeadura a intervalos de sete dias. Foi empregado o delineamento inteiramente casualizado, com tres repeticoes. Cada unidade experimental constou de um vaso com 12 L de solo, onde 50 sementes de B. pilosa foram distribuidas. A primeira aplicacao, em cada sequencia de dias, foi feita com um quarto da dose; a segunda, com um quarto; e a terceira, com metade da dose. Foi empregado um pulverizador costal de CO2 com volume de calda equivalente a 200 L ha-1. A herbigacao foi feita com um simulador de irrigacao (4,52 mm ou 45.200 L ha-1). Na pulverizacao, houve excelente controle da planta daninha com as doses de 100, 150 e 200 g ha-1, independentemente da sequencia de dias da aplicacao. Na herbigacao, as aplicacoes sequenciais foram ineficazes.

Seletividade e controle de plantas daninhas com oxyfluorfen e sulfentrazone na implantação de lavoura de café

This study aimed to evaluate oxyfluorfen and sulfentrazone selectivity and weed control in young coffee plantations (Coffea arabica cv. Red Catuai). Three trials were conducted in a randomized complete block design, with 10 treatments and four replicates. In the first and second trials, at 30 and 90 days after transplanting (DAT), respectively, two doses of oxyfluorfen (0.36 and 0.72 kg a.i. ha-1) and sulfentrazone (0.4 and 0.6 kg a.i. ha-1) were tested by spraying the herbicides directly into soil (with seedling protection) or onto the total area. The same herbicides and doses were used in the third trial, but at 300 DAT and only directed to the soil, using two sprayer nozzles with different drift potentials being tested. Two additional control plots were added: hand-weeding control and weedy treatments. Weeds present in the inter-row spaces were eliminated by mowing operations. Weeds and their densities were identified. The toxicity of the herbicides to the coffee plants and its effectiveness in controlling the weeds were assessed. The main weed occurring in the experimental area was Brachiaria decumbens. Visual symptoms of herbicide toxicity were observed only when the herbicides were applied in the entire area (trials 1 and 2), regardless of their doses and application times. At the third herbicide application trial, no visual symptoms of herbicide toxicity and no reductions in plant growth were observed, regardless of the herbicide, the dose and the sprayer nozzles tested. At all times, a very good weed control percentage was obtained, but selectivity occurred only when the herbicides were not applied onto the total area.

Energetic Analysis of a Low Cost Solar Heater

The objective of this study was to analyze the utilization of recyclable and low cost materials for solar water heating. A tubular solar water heater prototype whose dimensions were 0.05 x 0.03 x 6 m with a wall thickness of 3 mm was constructed and evaluated. The prototype was painted flat black and surrounded by transparent PET bottles. Evaluation of the collector considered of reading water temperature between 10:00 AM and 4:00 PM with 6 daily measurements on July 2, 3 and 4 of 2004. During evaluating the water flow rate remained constant at 20 L h-1. The results showed that the developed collector presented an energetic absorption of 2.33 kWh day-1 which represents 7.77 kWh day-1m-2 of collector. It was concluded that the developed collector possesses a strong social character, as well as being a rational alternative for Brazilian energetic problems, contributing to the reduction of electricity transmission and distribution.