Technical the application of glyphosate to agricultural product certifications / Tecnologia de aplicação do glyphosate para certificação de produtos agrícolas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This study was carried out to define parameters for glyphosate application in controlling the Brachiaria decumbens grass, by using a centrifugal pulverization system to establish possible technical criteria that can be screened. The pulverization system was developed on such a way to provide uniform pulverization conditions, therefore turning possible the obtainment of repeatability in applications. The technical characteristics concerning to the profile and volumetric distribution uniformity, besides the spectrum and population of the drops provided by different operational conditions. Then, those doses of the glyphosate CS 360 more appropriate to controlling B. decumbens were selected under greenhouse conditions and were used to establishing the technical parameters of the herbicide application technology. To establishing those parameters, the treatments consisted of thirty combinations provided by five rotations of the rotary device of the centrifugal sprayer (105, 157, 210, 262 and 315 rad s-1) and six displacement speeds (0,5; 1,0; 1,5; 3,0; 4,5; 6,0 Km h-1). The volumetric medium diameter (DMV), the population density of the spraying drops (DEN) and the percent target covering (COB) were evaluated, then related to the effectiveness in controlling B. decumbens. The treatments were analyzed at 20, 40 and 60 days after emergency of the plants. The entirely randomized experimental design was used with 30 treatments, three controls and five replicates. A total of 465 experimental units were constituted by polyethylene pots. The multiple regression analysis was used to analyze the data, and the choice of the models was based on either significance of the regression coefficients and the determination coefficient (R2). To validate the treatments, a field assay was accomplished, by using three treatments that provided satisfactory controls under greenhouse conditions. The experiment was set up under a factorial scheme 3 x 3, that is three spraying speeds (3.5; 5.5 and 6.5 km h-1) and three glyphosate doses (300, 720 and 1,080 g ha-1), according to the randomized block design. The experimental units consisted of 15m2 areas, composed by B. decumbens pasture. Four hydraulic nozzles that would provide spectra and populations drops similar to those with satisfactory control obtained under greenhouse conditions were selected. The results for effectiveness in the assay under field and greenhouse conditions were analyzed as a function of visual analyses and dry biomass. The centrifugal spraying provided higher liquid distribution at extremities, relative to the center of the spraying jet center, for all rotations under analysis. This resulted into high variation coefficients in the volumetric distribution uniformity, when profiles were separately analyzed. Higher rotations provided higher volumetric distribution uniformities and higher useful spraying ranges. The drop diameters decreased as the rotations and sprayer speeds were increased. Those changes were progressively lower, so indicating there was a minimal limit of the drop diameters. The drop densities and the covering percentage showed positive linear response with the rotations, but linear negative response with the displacement speeds. At 30 DAA, the dose of 100 g ha-1 glyphosate caused 89 % reduction in the dry biomass content of the plants, when applied at 20 DAE. At 40 and 60 DAE, the dose of 400 g ha-1 caused 100 % reduction in the dry biomass. DMV and COB present negative sign, therefore showing that as the diameter of the produced drops and the percent target covering are increased, the reduction in the control effectiveness occurs. However, the positive sign found for DEN averages rather points out the increased effectiveness of the treatments, when densities of the drops deposited on the target are increased. Optimum controls (>91%) can be obtained, by operating the sprayer on such a way to provide DMV of 327, 441 and 487 m, covering of 2.51, 4.59 and 5.58 % for the growth stages 20, 40 and 60 DAE of the plants, respectively, since DEN is 30 drops cm-2.

ASSUNTO(S)

herbicidas rastreabilidade application techniques herbicide certification tecnologia de aplicação engenharia agricola

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