L.R. Ferreira

Distribuição volumétrica e espectro de gotas de pontas de pulverização de baixa deriva

Objetivou-se neste trabalho avaliar a distribuicao volumetrica e o espectro de gotas das pontas de pulverizacao de baixa deriva TTI110015, AI110015 e AVI11001 sob diferentes condicoes operacionais. A distribuicao volumetrica foi determinada em bancada de ensaios padronizada analisando o coeficiente de variacao (CV%) de uma barra simulada em computador, utilizando pressoes de 200, 300 e 400 kPa, altura de 30, 40 e 50 cm em relacao a bancada e espacamento entre pontas de 40 a 100 cm. O espectro de gotas foi produzido utilizando-se apenas agua como calda em um analisador de particulas em meio aquoso, nas pressoes de 200, 300 e 400 kPa. Foram avaliados o DMV, a porcentagem de gotas com diâmetro inferior a 100 µm (%100 µm) e a amplitude relativa (AR). As pontas proporcionaram perfil descontinuo nas pressoes de 300 e 400 kPa e uniforme a 200 kPa. Na pressao de 200 kPa, as pontas foram adequadas apenas para aplicacao em faixa, e a 300 e 400 kPa, apenas para area total. Ocorreu menor CV (abaixo de 7%) com a maior pressao de trabalho e menor espacamento entre pontas. A medida que se aumentou a pressao de trabalho, reduziu-se o DMV. As pontas TTI110015 e AI110015 em todas as pressoes e a ponta AVI11001 na pressao de 200 kPa produziram gotas extremamente grossas e gotas grossas nas pressoes de 300 e 400 kPa apenas para a ponta AVI11001. As pontas proporcionaram baixos valores de amplitude relativa (AR) e gotas de tamanho uniforme, bem como produziram baixa porcentagem de gotas menores que 100 µm, principalmente TTI110015 e AI110015, com menor risco de deriva.

Comportamento de cultivares de milho no consórcio com Brachiaria brizantha na presença e ausência de foramsulfuron + iodosulfuron-methyl para o manejo da forrageira

O objetivo deste trabalho foi avaliar o comportamento de cultivares de milho no cultivo consorciado com Brachiaria brizantha cv. MG5 Vitoria e o efeito da aplicacao de subdose da mistura dos herbicidas foramsulfuron + iodosulfuron-methyl no manejo de B. brizantha, numa area sem interferencia de plantas daninhas, em sistema de plantio direto. Cinco cultivares de milho foram avaliados: um hibrido simples (AGN 30A00), um hibrido simples modificado (30K75), dois hibridos duplos (RG2A e AGN 25A23) e uma variedade (UFV M100), conduzidos em dois sistemas de manejo de B. brizantha: com e sem aplicacao de 30 g ha-1 da mistura comercial de foramsulfuron + iodosulfuron-methyl (300 + 20 g kg-1). O delineamento experimental foi de blocos ao acaso, em parcelas subdivididas, com quatro repeticoes, sendo os cultivares de milho colocados nas parcelas principais e os sistemas de manejo de B. brizantha nas subparcelas. A aplicacao do herbicida foi realizada aos 30 dias apos a emergencia do milho (DAE). Aos 30, 60, 90 e 120 DAE foram efetuadas avaliacoes da massa seca da parte aerea de B. brizantha. Para cultura do milho, na ocasiao da colheita, que ocorreu aos 120 DAE, avaliaram-se a altura de plantas, o estande final e o rendimento de graos. Verificaram-se maiores valores do rendimento de graos de milho para os cultivares 30K75, AGN 30A00 e RG2A. Os hibridos simples (AGN 30A00) e simples modificado (30K75) foram mais competitivos com a forrageira, reduzindo o acumulo de massa seca, em relacao aos hibridos duplos e a variedade. A aplicacao do foramsulfuron + iodosulfuron-methyl reduziu a taxa de crescimento de B. brizantha, sem, no entanto, afetar o rendimento de graos de milho. Com isso, fica demonstrado que a forrageira nao influenciou o rendimento da cultura, com o consorcio implantado em semeadura simultânea.

Interferência de plantas daninhas na cultura de algodão em sistema de plantio direto

An experiment was conducted in clay soil texture, in Vicosa-MG, Brazil, during the growing season 1989/1999, to evaluate the periods of weed coexistence in a cotton crop under no-tillage. The treatments were: 0, 15, 30, 45, 60 and 75 days after crop seeding under weed coexistence, and maintained weed free until crop harvest. The plots consisted of six rows 4 m long, and 0.9 m spaced, with six plants per meter. At the end of each coexistence period, the weeds were evaluated, by determining the number of species and shoot dry matter weight. The average crop plant height was also evaluated; 125 days after emergence (DAE), boll numbers per plant, and node numbers until insertion of the first fruitful branch were also evaluated, while cotton productivity was evaluated at harvesting. The average accumulation of the total dry matter of weeds was 4.7 g m-2 day-1. When comparing the treatments with and without weed interference, it was observed that weed interference throughout the cycle increased the average node numbers until insertion of the first fruitful branch, but reduced the average boll numbers and height of the plants. Weed interference throughout the cotton plant cycle caused a reduction of 81.2% in cotton productivity. Considering the 5% loss in productivity as acceptable, the period previous to weed interference was14 DAE.

Consórcio entre feijão e Brachiaria brizantha sob doses reduzidas de graminicida

The objective of this work was to evaluate Brachiaria brizantha intercropped with BRS Valente and Diamante Negro bean cultivars under reduced rates of fluazifop-p-butyl. The experiment was conducted in a randomized complete block arrangement, with four replications, in a split-plot design. The bean cultivars intercropped with B. brizantha constituted the plot (Diamante Negro and BRS Valente) and the doses of fluazifop-p-butyl the split-plots. B. brizantha and the bean cultivars were evaluated in monocrop kept clean by hand hoeing. Final stand, grain yield, 100-seed weight, number of pods per plant and number of seeds per pod of bean cultivars were evaluated. B. brizantha was collected 25 days after BRS Valente cultivar harvest, evaluating aerial dry biomass of the aerial part and canopy height. BRS Valente and Diamante Negro, were not affected by B. brizantha intercrop; it was observed that BRS Valente cultivar (1.80 t ha-1) was more adequate for this planting timing, in relation to Diamante Negro cultivar (1.31 t ha-1). Bean plants were very competitive with B. brizantha reducing forage dry biomass of 50% relative to B. brizantha monocrop. Intercrop without herbicide compared to 15 g ha-1 of fluazifop-p-butyl showed that the treatment with herbicide reduced in 12 and 13% the dry biomass and canopy height, respectively. Above 21 g ha-1 of fluazifop-p-butyl, the forage showed highly susceptible to the herbicide, presenting an extremely reduced biomass accumulation.

Misturas de herbicidas no manejo de plantas daninhas na cultura do feijão

Avaliou-se a eficacia da combinacao dos herbicidas fomesafen, fluazifop-p-butil e bentazon no manejo integrado de plantas daninhas do feijoeiro (plantio direto e convencional), cultivados em areas anteriormente com milho para grao e silagem. Foi avaliado tambem o residuo do fomesafen no solo aos 125 dias apos a aplicacao (DAA). No plantio convencional, Cyperus rotundus foi a especie dominante, enquanto no plantio direto a infestacao dessa especie foi muito baixa. Nenhuma das combinacoes de herbicidas foi eficiente no controle de C. rotundus. Com excecao de fluazifop-p-butil + bentazon (125 + 480 g ha-1), todas as combinacoes foram eficientes no controle das especies daninhas dicotiledoneas. Nao houve efeito dos tratamentos de herbicidas na produtividade do feijoeiro. O fomesafen, aplicado no plantio direto, causou toxicidade no feijao a partir da dose de 100 g ha-1, sobretudo no milho para silagem. No plantio convencional, sintomas mais leves somente foram observados na dose de 200 g ha-1. Houve residuo de fomesafen no solo apenas na area de plantio direto onde nao havia palhada sobre a superficie do solo, ou seja, na area anteriormente cultivada com milho para silagem. E possivel reduzir doses do fomesafen quando misturado ao bentazon sem afetar a produtividade do feijoeiro. Em areas de feijao cultivado apos colheita do milho para silagem e importante o uso de doses pequenas do fomesafen, para evitar toxicidade a culturas sensiveis subsequentes.

Efeitos do trinexapac-ethyl sobre o crescimento e florescimento da grama-batatais

The objective of this work was to evaluate the efficiency of doses and application intervals of trinexapac-ethyl on the vegetative growth and flowering of bahiagrass, to reduce clips and improve lawn quality. The experiment was conducted on the campus of the Federal University of Vicosa, in Vicosa-MG - Brazil, from December 1998 to March 1999, in an established lawn. The experiment was arranged in a randomized complete block design, with 13 treatments and four repetitions, distributed in a factorial scheme (6 x 2 + 1), with six doses of trinexapac-ethyl (0.00; 0.25; 0.50; 0.75; 1.00 and 1.25 kg ha-1), applied two and five days after lawn clipping and a control with clipings every three weeks. Evaluations were made at three, six, nine and twelve weeks after clipping for total dry biomass production, and height and number of seedheads. For all the characteristics studied, a direct relationship was verified between the growth regulator trinexapax-ethyl dose increase and the timing of clipping of vegetative and flowering lawn growth. Thus, lawn clipings were avoided for up to 12 weeks by applying 0.75 kg ha-1 of the growth regulator. No application time or trinexapac-ethyl dose effects were observed on the coloration of the lawn.

Anatomical characterization of the leaf, stem and rhizome of Digitaria insularis

RESUMO - A anatomia da folha, de colmo e do rizoma de Digitaria insularis foi investigada,visando identificar caracteristicas que possam estar relacionadas a sua tolerância aoglyphosate. Sementes e rizomas de plantas adultas foram coletadas em campo, em area deplantio direto, onde o herbicida glyphosate vem sendo utilizado repetidamente ha variosanos. As plantas provenientes dessas sementes e desses rizomas foram cultivadas emvasos com capacidade de 3 L, contendo solo de textura media, em casa de vegetacao. Quan-do as plantas atingiram o estadio fenologico de pre-florescimento, foram coletadas tresfolhas totalmente expandidas por planta, entre o terceiro e o quinto no. Simultaneamente,coletaram-se fragmentos dos rizomas e os entrenos recobertos pelas bainhas das folhasamostradas. As amostras foram fixadas em FAA

Misturas de herbicidas para o controle de plantas daninhas do gênero Commelina

This research was conducted to evaluate the efficiency of herbicide mixtures in the control of two dayflower species, Commelina diffusa and Commelina benghalensis. These species were grown from stem segments in 12 L pots during 120 days. Subsequently, a randomized complete block design with four replicates was performed for each species. The treatments were carfentrazone-ethyl combined to either glyphosate or glyphosate-potassium salt (30 + 720 g ha-1); glyphosate (720 g ha-1) combined to flumioxazin (60 g ha-1), or 2.4-D (670 g ha-1) or metsulfuron methyl (4 g ha-1); oxyfluorfen combined to sulfentrazone (480 + 375 g ha-1); sequential 21 day-spaced applications of (paraquat + diuron) / (carfentrazone-ethyl + glyphosate) (200+400) /(30+720) and (paraquat + diuron) / (paraquat + diuron) (200+400) / (200+400); and no herbicide application as check control. The percentage of weed control and shoot fresh weight were evaluated. The best treatments to control both species were the sequential applications of (paraquat + diuron) / (carfentrazone-ethyl + glyphosate) and of (paraquat + diuron) / (paraquat + diuron), followed by 2.4-D + glyphosate and carfentrazone-ethyl + glyphosate or glyphosate-potassium salt mixtures.

Efeito da irrigação inicial na profundidade de lixiviação do herbicida s-metolachlor em diferentes tipos de solos

The leaching depth of the herbicides applied on the soil often affects their selectivity to crops. This work aimed to study soil mobility of s-metolachlor in five types of soils (Red-yellow Podzolic, Purple Latosol, Red-yellow Latosol, Quartz Sand-organic and Quartz Sand), as well as to analyze the effect of the initial irrigation management on that process, through bioassays, relating the results found with possible phytotoxicity effects to irrigated crops. The experiments were carried out under, greenhouse conditions using mobility columns, consisting of eight treatments combining two types of initial irrigation (25 mm water lamina irrigated before and after s-metolachlor application), with four soil layers (0-5, 5-10, 10-15 and 15-20 cm), and five types of soils. S-metolachlor rate sprayed was 1.92 kg a.i. ha-1 for all the treatments and the test plant seeded in the plots was the Sorghum bicolor, hybrid BR 304. A tendency for greater s-metolachlor mobility and availability was observed in all soils, when irrigation was accomplished after herbicide application. The largest mobility and availability of s-metolachlor was observed in the Quartz Sand soil. In all types of soils, s-metolachlor concentrated in the superficial layer (0-5 cm). It was concluded that soils with low levels of organic matter and smaller effective CEC increase the predisposition for occurrence of s-metolachlor phytotoxicity effects to the crops, as well as the probability of underground water contamination.

Deriva simulada do glyphosate em cultivares de café Acaiá e Catucaí

This study aimed to evaluate the effects of simulated glyphosate drift on the growth of two cultivars with distinct growing patterns. The experiment was arranged in a randomized block design, with four repetitions, and the treatments were distributed in a factorial scheme 2x5, with two cultivars in the first factor and the glyphosate subdoses (0, 57.6; 115.2; 230.4 and 460.8 g ha‑1) in the second factor. On the day glyphosate was applied and at 45 and 120 days after application (DAA), height, leaf area, stem diameter, and number of plagiotropic branches and leaves were evaluated; at 10, 45 and 120 DAA, plant intoxication symptoms were visually evaluated and at 120 DAA, dry mass accumulation of the stem, leaves, and roots was evaluated. The intoxication symptoms of the coffee plants caused by glyphosate were characterized by chlorosis and leaf narrowing in the two cultivars studied. However, more severe symptoms were verified in the Acaia cultivars from 10 DAA on, such as necrosis of younger leaves in the median part of the plant. It was concluded that Acaia cultivar is less tolerant to glyphosate than Catucai cultivar, since it showed lower growth when submitted to herbicide treatment, i.e., tolerance can vary between cultivars with distinct growing patterns.