Produtividade e qualidade da fibra de algodoeiro submetido a aplicação de subdoses de 2,4-d sal colina

Abstract

Cotton is considered one of the most sensitive crops to 2,4-D herbicide. However, it is known that subdoses of herbicides may not compromise or provoke stimulating effects in qualitative and productive aspects of crops of interest. Thus, the objective of this work was to evaluate the effect of subdoses of 2,4-D choline salt on the productive aspects and fiber quality of herbaceous cotton at different phenological stages. The experimental design was in randomized blocks, with four replications and treatments distributed in factorial design 9 x 3 (nine fractions of the 2,4-D herbicide choline salt formulation: 0; 0.4275; 0.855; 1.71; 3 .42; 8.55; 17.1; 34.2 and 68.4 g ea ha-1 , associated with three phenological stages of cotton: V4, B4 and C4). The plants were evaluated for the main production parameters and fiber quality of the cotton. The results were subjected to analysis of variance and, when significant, the hormesis model was tested in order to describe the dose-response curves for low dose stimuli. When applied at stage V4, fractions of the 2,4-D choline salt herbicide negatively affect the cotton crop. Fractions of the 2,4-D choline salt herbicide applied at the B4 stage of cotton can increase all the production variables of the crop. No underdose of the 2,4- D choline salt herbicide affected fiber quality variables. Contaminations of 2,4-D choline salt in cotton stages V4 and B4 affect some quality characteristics of cotton fiber. The productive and quality aspects of cotton fiber at stage C4 were not influenced by the application of subdoses of 2,4-D choline salt.