Efeito de diferentes doses de fomesafen no crescimento e desenvolvimento de trigo

Abstract

The persistence potential of a herbicide in the soil is determined by its physical and chemical characteristics, the dose used, the soil characteristics, environmental conditions, and other key factors to predict problems in succession crop development. The aim of this experiment was to evaluate the behavior of wheat cultivated in soil contaminated with the herbicide fomesafen. The experiment consisted of a bioassay conducted in a controlled environment at the Federal University of Fronteira Sul (UFFS), Campus Laranjeiras do Sul-PR, where the substrate free of herbicide contamination was allocated in 8 dm³ polyethylene pots, and the herbicide applied directly to the substrate just before wheat sowing. The experiment was conducted in a completely randomized design with four replications, where fomesafen doses of 0.0; 0.25; 0.5; 0.75; 1.0 (recommended dose) and 2.0 Lha-1were tested. The following variables were evaluated: phytotoxicity (%), stand over time, plant height, mortality, shoot and root green mass and shoot and root dry mass. The data were submitted to normality and variance analysis by the F test, all tests were performed at 5% probability and the relationship between the product doses and the evaluated variables were subjected to regression analysis. It was observed that fomesafen subdoses in the soil promoted interference in plant height, dry matter accumulation in the shoots and roots, as well as promoted high phytotoxicity indexes causing even the death of plants and consequently loss of stand in all tested doses. It can be seen that fomesafen had negative effects on wheat development, even at low doses of the product, which of course will also impair the grain yield of this crop. As the symptoms of phytotoxicity and mortality were increasing as the doses were increased, care should be taken in prescribing the fomesafen dose when one wishes to cultivate wheat in succession as there is great potential for crop damage.