Manejo antecipado de Conyza spp. através de atrazina + mesotrione: Dessecação pré-semeadura, controle de novos fluxos germinativos e Carryover em soja

Abstract

Pre-sowing desiccation of Conyza spp. is influenced by climatic conditions, affecting its foliar structure, residual effects of pre-emergent herbicides, and soybean phytotoxicity. Therefore, this study aimed to evaluate the efficacy of Conyza spp. control using (atrazine + mesotrione) + triclopyr at different intervals between application and soybean sowing, the phytotoxic effects on this crop, and the residual atrazine. To this end, a field experiment was conducted with the following geographic coordinates: 22° 13´ 52,4495'' south latitude and 54° 59´ 10,5372'' west longitude with Conyza spp. infestation, in a randomized block design. The application of (atrazine + mesotrione) + triclopyr (500+50+1020 g a.i. ha-1) was performed at 60, 45, 30, 15, and 0 days before soybean sowing (DBS) and sequential glufosinate ammonium (500 g a.i. ha 1) after 15 days. Climatic conditions and soil matric potential were monitored. Visual assessments of Conyza spp., germination flow, and scanning electron microscopy (SEM) were performed. Atrazine residual was evaluated by high-performance liquid chromatography (HPLC) at 0, 3, 5, 7, 14, 21, 28, 35, and 42 days after initial application (DAI) and at the time of soybean sowing and phytotoxicity. Statistical analyses were of the GAMLSS type. Conyza spp. control varied depending on application periods and height; the lower the soil matric potential at the time of application, the longer it took to establish percentages above 80%. In SEM, the greatest intensity of damage to foliar structures was observed in the application at 15 DBS. The concentration of atrazine in the soil gradually decreased over time; for the 60 DBS period, 389 and 19.58 g a.i. ha-1 of atrazine were obtained at 0 and 42 DAI, respectively. At the time of soybean sowing, 415.75; 372; 322.33; 284.58; and 121.25 g a.i. ha-1 of atrazine were obtained. It is concluded that climatic conditions influence the residual effects of herbicides and their control efficacy.