Uso de herbicidas associados a adjuvante e fertilizante nitrogenado no controle de Digitaria horizontalis, Eleusine indica e Conyza bonariensis

Abstract

Weed control is one of the main challenges for the sustainability and productivity of agricultural systems. Species such as Digitaria horizontalis, Eleusine indica, and Conyza bonariensis present a high infestation capacity and resistance to conventional chemical control, demanding integrated and efficient strategies. Among the available alternatives, the combined use of herbicides, adjuvants, and nitrogen fertilizers stands out, as their interaction may enhance herbicidal action and improve foliar absorption. In this context, the present study aimed to evaluate the efficiency of the association between herbicides, adjuvants, and nitrogen fertilizers in the control of the three mentioned species, seeking to identify the most effective combinations and to understand the effects of these mixtures on chemical management performance. The experimental design was completely randomized, with four replications, using eight treatments for the grasses and five for the dicot species. Treatments were applied exclusively when the plants reached the four-leaf phenological stage. They involved different combinations of glyphosate, clethodim, 2,4-D, saflufenacil, an adjuvant, and a nitrogen-based fertilizer. Evaluations were performed at 7, 14, and 21 days after application (DAA), based on visual control ratings (%) and analysis of shoot dry mass. Results showed that treatment efficacy varied according to the evaluated species and the product combinations. For D. horizontalis, the treatment composed of glyphosate + clethodim + adjuvant + fertilizer achieved the highest control, reaching 83.75% at 21 DAA. In C. bonariensis, only the treatment including glyphosate + 2,4-D + saflufenacil provided control above 90%, being significantly more effective than the others. In E. indica, the best performance was observed with clethodim + adjuvant + fertilizer, although control levels remained below 50%. It can be concluded that the association of herbicides, adjuvants, and nitrogen fertilizers may significantly increase the effectiveness of weed control, especially for hard-to-control species. However, the results also indicate that the efficiency of these mixtures depends on the careful choice of components, the target species, and application conditions. The study highlights the need for complementary field trials focusing on agronomic validation, cost–benefit analysis, and assessment of the environmental impact of these combinations within integrated weed management.