Efficiency and toxicity of oxyfluorfen in irrigation water in field implantation of the Eucalyptus genus

Abstract

This research aimed to evaluate the toxicity of oxyfluorfen doses applied in pre-emergence via irrigation water in the implantation of eucalyptus crop, clone VCC865 (hybrid Eucalyptus urophylla x Eucalyptus grandis), in addition to its effectiveness in weed control. The experiment was conducted under field conditions, in experimental design in randomized block, with four replications, in a 5 x 2 x 2 factorial scheme: five doses of oxyfluorfen herbicide (0, 360, 720, 1080 and 1440 g a.i. ha^-1), two forms of application (on the plant and on the soil) and two volumes of irrigation water (5 and 10 L). The treatments were applied manually 15 days after planting the seedlings using a watering can. Eucalyptus intoxication percentage, plant height, collar diameter, leaf number, leaf area, shoot dry mass, relative chlorophyll content, stomatal conductance, internal CO₂ concentration, photosynthetic rate and respiration rate were evaluated. Weeds present in the useful area of the planting holes were identified and quantified to determine plant density in the sampled area by treatment. In the area of implantation of the eucalyptus, 27 species of weeds were identified, belonging to 23 genera and 11 botanical families, with greater occurrence of Chenopodium carinatum, Blainvillea biaristata and Urochloa decumbens. The oxyfluorfen in the irrigation water, regardless of the application form and the volume of irrigation water volume, was selective for the crop at the doses evaluated. The highest doses (1080 and 1440 g a.i. ha^-1) effectively controlled pre-emergence of weed growth, which increased initial growth of the eucalyptus plants, mainly in the leaf number, leaf area and accumulation of shoot dry mass.

Keywords:
Herbicide; Tolerance; Phytointoxication