Effects and management of foliar fungicide application on physiological and agronomical traits of soybean

Abstract

Among the main factors limiting the yield of soybean, diseases stand out as the most important and difficult to control, causing up to 100% loss in the crop. The occurrence of diseases in soybean in Brazil is directly related to the tropical climate. Thus, the need to maintain high yield led to an increase in the number of foliar applications with fungicides. The aim of the study was to evaluate the response to the increase number of foliar fungicide applications on physiological and agronomic aspects and the economic viability of this management, contributing to the research of fungicide management in soybean. The experiment was performed in Minas Gerais state, in two environments (Ijaci and Lavras), during 2014/15 crop year, with the cultivar BRSMG 850GRR. The experiment was performed in a randomized block design, in split-plot, with three replications. The plots were composed of the number of applications (0, 1, 2, 3, 4 and 5). The applications started at the R1 stage (beginning of bloom), with a 15-day interval to the next application (R1; R1+15d; R1+30d; R1+45d; R1+60d). The sub plots were composed of different chemical fungicides (Elatus, Fox, Opera, Orkestra, and BAS - 702 - a not registered product). Chlorophyll content, dry mass, crop cycle, plant height, number of pods, number of grains, thousand-seed weight, grain yield, harvest index, daily increment and economic viability were evaluated. Individual and joint variance analyses were performed. The means were grouped by the Scott-Knott test and the regression analysis was applied to study the sources of quantitative variation. The phenotypic correlation between the number of applications and the physiological and agronomic traits were also estimated. The increase in the number of foliar fungicide applications provides an increase in grain yield, thousand-seed weight, daily increment, dry mass and harvest index, and also provides changes in crop cycle, chlorophyll content and a higher net margin, generating a greater gain revenue.