E.A. Santos

Efeitos de diferentes formulações comerciais de glyphosate sobre estirpes de Bradyrhizobium

O objetivo deste trabalho foi avaliar efeitos de formulacoes comerciais de glyphosate sobre estirpes de Bradyrhizobium, em condicoes de laboratorio. As formulacoes foram aplicadas na concentracao de 43,2 µg L-1 do equivalente acido. As bacterias foram inoculadas em meio de cultura a base de manitol e extrato de levedura (YM). O efeito do herbicida no crescimento das estirpes de Bradyrhizobium foi avaliado mediante leitura da densidade otica em espectrofotometro. Avaliou-se o crescimento das estirpes de B. japonicum SEMIA 5079 e de B. elkanii SEMIA 5019 e SEMIA 587 sob efeito de nove formulacoes de glyphosate: Zapp Qiâ, Roundupâ, Roundup Multiacaoâ, Roundup Transorbâ, Roundup WGâ, Tropâ, Agrisatoâ, glyphosate tecnico [padrao de N-(phosphonomethyl) glycina] e controle sem adicao de herbicida (testemunha para as estirpes). Foram utilizadas seis repeticoes. Confeccionaram-se curvas de crescimento para cada estirpe. Pelos resultados, pode-se observar que todas as formulacoes de glyphosate causaram efeitos diferenciados sobre as estirpes de Bradyrhizobium SEMIA 5019, SEMIA 5079 e SEMIA 587. Constatou-se que a formulacao Zapp Qi foi a menos toxica as estirpes de Bradyrhizobium avaliadas. A maior toxicidade foi observada para Roundup Transorb, que provocou reducoes no crescimento acima de 94% para todas as estirpes de Bradyrhizobium estudadas. Nao se observou correlacao entre o tipo de sal - isopropilamina, amonio ou potassico, presentes na formulacao herbicida - e o grau de inibicao no crescimento das estirpes. SEMIA 587 foi a estirpe menos tolerante a maioria das formulacoes testadas, porem SEMIA 5019 foi a mais sensivel ao glyphosate padrao, sem adicao de sais ou de outros aditivos.

Fitorremediação do herbicida trifloxysulfuron sodium

This work aimed to evaluate the efficiency of plant species in the phytoremediation of the herbicide trifloxysulfuron sodium in soils, by using corn crop as a bioindicator. The treatments were composed by the combination of the species (Calopogonium muconoides, Crotalaria juncea, Crotalaria spectabilis, Vicia sativa, Cajanus cajan, Canavalia ensiformis, Helianthus annus, Dolichus lablab, Pennisetum glaucum, Stylosantes guianensis, Mucuna deeringiana, Mucuna cinereum, Mucuna aterrima, Raphanus sativus and Lupinus albus) sowed before the corn, without previous cultivation (control), and three rates of trifloxysulfuron sodium (0.00,3.75 and 15.00 g ha-1). The experiment was arranged in a randomized block design, in a factorial scheme, with three replicates. Eighty days after sowing, the plants were cut and the shoots discarded. After that, corn (cultivar AG-122) was sowed. Forty five days after emergence, corn height and shoot dry biomass were recorded. M. aterrima and C. ensiformis were considered efficient regarding decontamination of the herbicide residues in soil.

Seleção de plantas com potencial para fitorremediação de tebuthiuron

This study aimed to select tebuthiuron- tolerant plants to use them in phytoremediation programs in contaminated soils. The evaluated species were: Amaranthus hybridus, Crotalaria juncea, C. hyssopifolia, Chamaesyce hirta, Canavalia ensiformes, Helianthus annus, Pennisetum typhoides, Estizolobium aterrimum, Raphanus raphanistrum and Crotalaria incana. The experiment was carried out in a greenhouse, with a sandy-clay soil with 2.18 dag kg-1 of organic matter, in pots of 3 dm3 capacity. The experiment was arranged in a 10 x 4 x 4 factorial scheme in a randomized block design with three replications. The treatments consisted of: 10 species, four tebuthiuron doses (0.0; 0.5; 1.0 e 2.0 kg ha-1) applied in pre-emergence, and four evaluation times (15, 30, 45, and 60 days after sowing). Phytotoxicity, plant height and, above-ground, root and total biomass dry matter were evaluated. Canavalia ensiformes and Pennisetum typhoides were tolerant to tebuthiuron at the dose of 0.5 kg ha-1, and Estizolobium aterrimum up to the dose of 1.0 kg ha-1, with the latter showing less phytotoxicity symptoms and a smaller reduction of plant height, above-ground, root, and total biomass dry matter, as compared to the control treatment.

Época de dessecação anterior à semeadura sobre o desenvolvimento da aoja resistente ao glyphosate

The objective of this paper was to evaluate the best timing for Brachiaria brizantha desiccation with glyphosate, aiming at transgenic soybean sowing. Different desiccation times were established (2.880 g ha-1 of glyphosate) ranging from 21 to zero days before soybean sowing, with one (1.080 g ha-1) or two (1.080 + 1.080 g ha-1 ) glyphosate applications in postemergence, respectively at 15 and 40 days. At five days after the first application and during flowering, foliate number and dry matter, dry matter of the remaining aerial part, roots, and radicular nodules were evaluated. During the same time, soil samples were collected to determine basal respiration rate and microbial biomass. At the end of the cycle, soybean grain yield was determined according to the different treatments. Soybean growth was affected by postemergence application of glyphosate, decreasing plant dry matter. Soybean development improved when glyphosate was used for desiccation between 7 and 21 days before sowing. Higher negative impact against microbial biomass occurred when desiccation and sowing were performed at the same day. Without glyphosate application, control grain yield decreased in more than 40%, and, on average, 23% on the plants that received the herbicide in postemergence.

Fitoestimulação por Stizolobium aterrimum como processo de remediação de solo contaminado com trifloxysulfuron-sodium

This study aimed to evaluate the effect of microbiota associated to Stizolobium aterrimum rhizosphere on remediation of soil contaminated with trifloxysulfuron-sodium. The treatments were arranged in a factorial scheme 2x4 and consisted of samples of Stizolobium aterrimum rhizosphere soils cultivated for 60 days and non-rhizosphere or non-cultivated soil, all submitted to four contamination levels (0.0, 7.5, 37.5 and 375 g ha-1).. Samples were incubated for 30 days in appropriate recipients to evaluate unfastening of CO2 by microbial respiration) and biomass carbon quantification. Bioremediation efficiency was verified by using the bioassay technique, using sorghum to indicate the presence of herbicide residue. The S. aterrimum rhizosphere soil treated with trifloxysulfuron-sodium showed higher biological activity, evidenced by higher unfastening of CO2,. Rhizosphere soil samples showed higher microbial biomass, regardless of herbicide presence. It was concluded that microbiota contributed to soil decontamination, since sorghum growth on the rhizosphere soil was similar with or without trifloxysulfuron-sodium, while it was inversely proportional to the herbicide dose in the non-rhizosphere soil.

Ação de herbicidas sobre o crescimento de estirpes de Rhizobium tropici

This work aimed to evaluate the growth of Rhizobium tropici BR322 and BR 520 strains, used as inoculant on common bean in Brazil, in yeast extract manitol (YM) medium supplemented with different herbicides (bentazon, metolachlor, imazamox, fluazifop-p-butyl, fomesafen and paraquat). Fluazifop-p-butyl and fomesafen were evaluated pure and in a commercial mixture with concentration varying from 0.0 to 49.23 mg L-1. Cell growth was assessed by optic density readings in a spectrophotometer at 560 nm, being later converted to colony forming units per mL. Paraquat caused higher inhibition of cell growth, followed by the commercial mixture fomesafen and fluazifop-p-butyl. For the other herbicides, growth reduction was not significant. In general, BR 520 strain was more tolerant to the tested herbicides, except to paraquat. The herbicide concentration I50, (which decreased Rhizobium growth in 50%) could not be determined in the fomesafen concentrations tested, isolated or mixed to fluazifop-p-butyl. The highest reduction of 31.1% was observed in BR322 at the maximum tested concentration of the commercial mixture.

Fitorremediação de solo contaminado com trifloxysulfuron-sodium por diferentes densidades populacionais de feijão-de-porco (Canavalia ensiformis (L). DC.)

Objetivou-se neste trabalho avaliar a fitorremediacao do solo contaminado pelo herbicida trifloxysulfuron-sodium a campo, pela especie de adubo verde Canavalia ensiformis (feijao-de-porco) cultivada em diferentes densidades populacionais. O delineamento experimental utilizado foi o de blocos casualizados, em esquema fatorial 4 x 2, com quatro repeticoes. Os tratamentos foram compostos pela combinacao entre quatro densidades de plantio da especie vegetal feijao-de-porco (0; 8; 20; e 32 plantas m-2) e duas doses do trifloxysulfuron-sodium (0,00 e 15,00 g ha1). Cinco dias apos o preparo do solo, o trifloxysulfuron-sodium foi aplicado antes da semeadura da especie fitorremediadora, a qual foi mantida na area por 65 dias. Apos esse periodo a area experimental foi novamente sulcada e fertilizada sendo cultivado feijao (Phaseolus vulgaris L. cv. Vermelho Coimbra), especie sensivel ao trifloxysulfuron-sodium. Aos 45 dias apos a semeadura do feijao avaliou-se a altura e a biomassa seca da parte aerea das plantas e ao final do ciclo da cultura, foram determinados o rendimento de graos, o numero de vagens por planta e o peso de 100 sementes. O cultivo previo de C. ensiformis nas densidades populacionais de 8, 20 ou 32 plantas m-2 promoveu a remediacao do herbicida. A densidade populacional minima de C. ensiformis que proporciona maior rendimento de graos a cultura do feijao e de 20 plantas m-2.

Fitorremediação de solo adubado com composto orgânico e contaminado com trifloxysulfuron- sodium

Objetivou- se neste trabalho avaliar a capacidade remediadora das especies vegetais feijao- de- porco (Canavalia ensiformis) e mucuna- preta (Stizolobium aterrimum), em solo adubado com composto orgânico e contaminado com o herbicida trifloxysulfuron- sodium. Na primeira etapa, avaliou- se o crescimento de C. ensiformis e S. aterrimum nos diferentes substratos, contaminados ou nao com herbicida. Os tratamentos foram compostos pela combinacao entre duas doses do herbicida trifloxysulfuron- sodium (0,0 e 7,5 g ha- 1) e cinco teores de composto orgânico: 0, 25, 50, 100 e 200 m3 ha- 1 (equivalentes a 0, 1,25, 2,5, 5 e 10% do volume de solo em cada vaso, respectivamente), dispostos em esquema fatorial 2 x 5, sob delineamento inteiramente casualizado, com tres repeticoes, para cada especie remediadora. Um dia apos a aplicacao do herbicida a superficie do solo, procedeu- se a semeadura das especies remediadoras, deixando- se como testemunha vasos sem planta. Na colheita, aos 60 dias apos a emergencia, avaliou- se a altura e a massa seca da parte aerea (MSPA) dessas especies. Todo o material colhido foi triturado e incorporado ao solo dos seus respectivos vasos. Na segunda etapa, avaliou- se a capacidade remediadora de C. ensiformis e S. aterrimum. Os tratamentos foram compostos pela combinacao entre cinco teores de composto orgânico e cinco tipos de cultivo previo: cultivo de C. ensiformis e S. aterrimum na presenca e ausencia do herbicida trifloxysulfuron- sodium e um tratamento sem cultivo previo e com aplicacao de trifloxysulfuron- sodium, dispostos em esquema fatorial 5 x 5, sob delineamento inteiramente casualizado, com tres repeticoes. Amostras de 100 g de solo foram retiradas dos vasos (6 L) usados na primeira etapa e colocadas em vasos de 100 cm3. Em seguida, cultivou- se sorgo (Sorghum bicolor) para indicacao de residuo do herbicida no solo. Essas plantas foram colhidas 20 dias depois, epoca em que se avaliaram a altura, a MSPA e o grau de intoxicacao delas pelo herbicida. No solo com trifloxysulfuron- sodium e sem cultivo previo das especies remediadoras, as plantas de sorgo tiveram seu crescimento reduzido, mesmo com a adicao de composto orgânico. O cultivo previo de C. ensiformis e S. aterrimum proporcionou crescimento normal as plantas de sorgo, confirmando a capacidade remediadora dessas especies. A adicao de composto orgânico nao influenciou a capacidade remediadora das especies.

Efeito da umidade do solo sobre a capacidade de Canavalia ensiformis e Stizolobium aterrimum em remediar solos contaminados com herbicidas

This paper aimed to evaluate the effect of soil humidity on Canavalia ensiformis and Stizolobium aterrimum capacity of remediating soil contaminated with tebuthiuron and trifloxysulfuron-sodium. The experiment was divided into two stages. In the first stage, soil at different levels of humidity were used, contaminated or not with herbicide, to evaluate C. ensiformis and S. aterrimum growth. Treatments consisted of a combination of tebuthiuron, trifloxysulfuron-sodium and herbicide absence, associated to four levels of soil water content (0.287, 0.358, 0.431 and 0.575 kg kg-1), arranged in a 3 x 4 factorial scheme, in a completely randomized design, with three replicates for each species. Trifloxysulfuron-sodium or tebuthiuron were applied on soil surface after preparing the substrate and filling the pots, and the species were sowed one day after that. At this stage, pots with same humidity level and under the same conditions, but without remediating plants, were used as control. After 60 days, plants were harvested to evaluate height and dry matter of ground tissue. All material was ground and incorporated into soil of their respective pots. At the second stage, the remediating capacity of C. ensiformis and S. aterrimum was evaluated. Treatments consisted of five humidity levels and five types of prior cultivation, arranged in a 4 x 5 factorial scheme, in a completely randomized design, with three replicates.Samples of 0.5 kg of soil were taken out from the pots previously used and placed in 0.5 L pots, where sorghum (Sorghum bicolor) was cultivated to trifloxysulfuron-sodium and soybean (Glycine max) to tebuthiuron. After 20 sowing days, plants were harvested to evaluate height, ground tissue dry matter and their intoxication level. C. ensiformis did not survive up to 60 days after sowing in tebuthiuron-contaminated soil, at any humidity level, and S. aterrimum survived when cultivated in soil between 0.287 and 0.358 kg kg-1 humidity. S. aterrimum was more efficient than C. ensiformis in soil decontamination with tebuthiuron. Sorghum and soybean grew better in soil contaminated with trifloxysulfuron-sodium or tebuthiuron, with prior cultivation, than in soil without prior cultivation. In general, remediation was not affected by humidity variation, with the effects on the development of remediating species being observed. C. ensiformis and S. aterrimum developed best in soil with humidity around 0.431 kg kg-1; however, at this level, tebuthiuron is more easily available for the soil solution.

Impacto do glyphosate associado com endossulfan e tebuconazole sobre microrganismos endossimbiontes da soja

The objective of this work was to evaluate the effects of glyphosate, in sequential applications, and its interaction with endosulphan + tebuconazole on mycorrhizal colonization, nodulation, and leaf concentrations of P and N of soybean plants. The experiment was conducted in the field in a Yellow-Red Argisol in the 2007/2008 crop year. Ten treatments were installed in split plots following a randomized block design with four replications. Endosulphan + tebuconazole application was done in the main plots, while the different methods of weed control in the sub-plots (unhoed control, hoed control, single application of glyphosate, sequential application of glyphosate, single application of fomesafen + fluazifop-p-butyl). Shoot and nodule dry matter, nodule number, mycorrhizal colonization, and N and P concentrations were evaluated when the soybean plants reached the R2 stage. Glyphosate and fomesafen + fluazifop-p-butyl did not cause reductions in nodule dry matter, except in the presence of endosulphan + tebuconazole. Glyphosate in sequential applications, in the absence of endosulphan + tebuconazole, promoted decreases in nodule number. Fomesafen + fluazifop-p-butyl and glyphosate in sequential applications negatively affected N concentrations in the leaves compared to the hoed control, in the absence of endosulphan + tebuconazole. Glyphosate did not affect the mycorrhizal colonization regardless of the application of endosulphan + tebuconazole. However, fomesafen + fluazifop-p-butyl led to increases in the mycorrhizal colonization in the absence of endosulphan + tebuconazole. Glyphosate applied sequentially on soybean plants, under the conditions studied, did not affect the mycorrhizal colonization and nodulation.