(PT) Controle químico de gramíneas exóticas e impacto ambiental de herbicidas na Floresta Nacional de Carajás.

Author(s): CASTILHO, Alexandre Franco
Summary: The occurrence of exotic flora and fauna in certain environments are potentially harmful to the species and relations trophic chains, may cause environmental impacts of great magnitude. In Carajás National Forest there occurrence of several species of exotic grasses, especially the genus Urochloa, which has adapted very well in the conditions of the region. This fact worries environmental agencies due to the threat of these species to biodiversity. The control of Urochloa plants genre has great efficiency through the use of herbicide to glyphosate molecule. Given this context, aimed at evaluating the chemical control of exotic grasses present in the Carajás National Forest. Two experiments were conducted in order to assess: i) The effect of different formulations and increasing doses of glyphosate in control of Urochloa humidicola and Urochloa brizantha and ii) Soil microbial activity as bio-indicator of the environmental impact of glyphosate. The first experiment was conducted in two experimental areas within the National Forest of Carajás, one with occurrence of Urochloa humidicola and one with U. brizantha. Experimental blocks were used in a 4 m x 7 m (28 m²) where we proceeded to treatment application. Three commercial formulations of glyphosate were used (Roundup Original®, Roundup Ultra® and Roundup WG®) at doses of: 0; 240; 480; 720 and 1440 g of active ingredient in equivalent acid ha-1 . The experimental design was randomized blocks with four replications. To control efficiency, was used visual toxicity evaluation of symptoms, assigning notes according to the symptoms of toxicity in the aerial part, in base ranging from 0 to 100%, with 0% representing no injury and 100% plant death. The best dose was established as that which provided 90% control. Regression equations were adjusted to account for the biological phenomenon in the evaluated variables. In the second experiment it was done soil collection 0-10 cm in the experimental area inside the FLONA Carajás, with subsequent screening and air-drying. Plastic pots with a volume of 800 ml were coated with polypropylene plastic bags, filled with 500 g of soil, the same treatments of the first experiment, being evaluated its effect on microbial activity in two moments which were subsequently applied: immediately after application and 28 days after application. They analyzed the microbial biomass carbon (MBC), microbial respiration and metabolic quotient. It was made analysis of variance at 5% probability by F test and comparison of means by Tukey test at 5% probability. Distinct medium of the testimony (dose 0.00) were considered to impact of the herbicide on the microbial activity. In the first trial was observed in all cases, an increase in the percentage of control plants U. humidicola and U. Brizantha with increasing doses of herbicides with subsequent stabilization. To U. humidicola the lowest dose which gave 90% control was 318 g a.i. in equivalent acid ha-1 of Roundup Ultra® formulation. For Urochloa Brizantha the lowest dose which gave 90% control was 873 g a.i. in equivalent acid ha-1 of Roundup WG® formulation. In the second experiment it was not observed negative impact of the use of any dose and formulation studied the soil microbial activity.
Year: 2015
Pages: 65 f.
Year of publication: 2015
Supervision: Nei de Melo Rivello
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Course: Master's Degree in Sustainable Use of Natural Resources in Tropical Regions