Impacto do glyphosate associado ao endossulfan e tebuconazole sobre microbiota do solo na cultura da soja

• Autor(a) principal: Reis, Marcelo Rodrigues dos
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1110
• topic: Soja transgênica; Nodulação; Microrrização; Transgenic soybean; Nodulation; Mycorrhizal colonization; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

The adoption of transgenic plants can lead to an increased use of glyphosate. This product associated with other pesticides can negatively affect the environment. Thus, the objective of this work was to evaluate the impact of glyphosate, endosulphan, tebuconazole, and fomesafen + fluazifop-ρ-butyl applications on the soil microbiota and on the endosymbiotic microorganisms and mineral nutrition of Roundup Ready. The physiological quality of seeds under the same conditions was also evaluated. An experiment was conducted in the field at the experimental station of Universidade Federal de Viçosa, Coimbra, Minas Gerais State (S 20° 45 20 and W 42° 52 40 ; altitude: 700 m), from December to April, 2007/2008 crop year, in a Yellow-Red Argisol. For microbial biomass, phosphate solubilization potential, CO2 evolution, and soil metabolic quotient determinations, soil samples were collected in the inter- row at 0- 10 cm depth. Mycorrhizal colonization and nodulation were determined in root samples collected from the soybean plants. The third trefoils from the shoot apices were also collected for micronutrient determinations. All samplings were done when soybean plants reached the R2 reproductive stage. The physiological quality of soybean seeds after harvesting was evaluated by the germination percentage, the first germination count, the soilless cold test, the accelerated aging test, the electrical conductivity, and the 100-seed weight. The pesticides did not affect the soil respiratory rates. The microbial biomass carbon was not affected by glyphosate or fomesafen + fluazifop-ρ- butyl application. However, decreases in the microbial biomass carbon and increases in the metabolic quotient were observed after the application of fomesafen + fluazifop-ρ- butyl associated with endosulphan + tebuconazole. Glyphosate, in single or sequential applications, did not affect the mycorrhizal colonization of the soybean plants, either treated or not with endosulphan + tebuconazole. Glyphosate and the mixture fomesafen + fluazifop-ρ-butyl did not affect nodule dry matter in the treatments without endosulphan + tebuconazole application. Leaf nitrogen concentrations were negatively affected by fomesafen + fluazifop-ρ-butyl and glyphosate in sequential application in the treatments without endosulphan + tebuconazole. These treatments did not affect nodule numbers and dry matter. Zinc and iron concentrations were not influenced by the pesticides. Copper and manganese concentrations were decreased after the sequential application of glyphosate associated with endosulphan + tebuconazole. The total germination percentages were not influenced by the herbicides, either associated or not with endosulphan + tebuconazole. The electrical conductivity and the germination percentages obtained by the soilless cold test were not affected by the weed plant control methods in the absence of endosulphan + tebuconazole. However, in the presence of endosulphan + tebuconazole, decreases in these variables were observed for seeds of plants treated with fomesafen + fluazifop-ρ-butyl. The mixture endosulphan + tebuconazole promoted a positive effect on seed vigor measured by the accelerated aging test. Among the methods for the control of weed plants, without endosulphan + tebuconazole application, the highest 100-seed weight was observed for the treatment corresponding to glyphosate in sequential application. In the presence of endosulphan + tebuconazole, no differences among the herbicides tested were observed for this variable. It is concluded that, under the conditions of the reported experiment, the use of glyphosate, associated with endosulphan + tebuconazole application, reduced leaf concentrations of copper and manganese in soybean. Also, no negative effects of this product on the soil microbial biomass, CO2 evolution, metabolic quotient, phosphate solubilization potential, mycorrhizal colonization, nodule numbers, nodule dry matter, seed germination, and seed vigor were observed.