Utilização de vapor associado a ácido pelargônico para a dessecação de plantas daninhas

Abstract

The desiccation of weeds present in no-till farming systems is becoming increasingly essential, and when the production system is agroecological, there are few effective alternatives for physical and bioherbicide management. Given this, the objective of this study was to evaluate the control efficiency of steam application at three different speeds, associated with different doses of pelargonic acid, in fallow areas. The experiment was implemented in a randomized block design with a subdivided plot scheme, with three speeds of steam machine movement (0.8 km h-¹, 1.3 km h-1, and 1.8 km h-1) in the plots. The subplots consisted of treatments without steam desiccation and with steam desiccation. Finally, the sub-subplots consisted of five doses of pelargonic acid (0%, 5%, 10%, 20%, and 40%) in a 100 L ha⁻¹ spray. The treatments were applied with a prototype steam generator and applicator machine on the soil surface over spontaneous vegetation composed of various weed species in the reproductive stage. As dependent variables, visual control assessments were performed 1, 3, 7, and 15 days after application, following a percentage control scale. Fifteen days after desiccation, samples of dry mass of green plants and dry mass of dry plants were collected using 0.25 m² samplers. The dry mass of these plants was quantified in terms of dry mass of green monocotyledonous plants, eudicotyledonous plants, total dry mass of green plants, and dry mass of dry plants in kilograms per hectare. The combination of steam applied at 0.8 km h⁻¹ with pelargonic acid showed the most promising results in weed desiccation compared to the other speeds, evidencing a synergistic effect between the physical and bioherbicide methods. Of all the doses of pelargonic acid with the use of steam, the 40% dose proved to be the most effective, showing that only the maximum dose of pelargonic acid used in this experiment obtained the best results. It should be noted, however, that heavy rain (50 mm in 30 minutes) about two hours after desiccation impaired the effects of the treatments, especially the bioherbicide, as even the most effective treatments showed insufficient weed control, below 50%. Therefore, further studies are needed to optimize the technology, improve operational performance, and reduce costs in order to enable its use as a sustainable alternative.