Abstract
Biodegradation studies of herbicides applied to the soil alone and in a mixture are required since herbicides are often used in combinations to control weeds. When herbicides are applied in mixtures, interactions may affect their environmental fate. Thus, the objective of this study was to evaluate the distribution of extractable residue, bound residue, biodegradation, and mineralization of diuron, hexazinone, and sulfometuron-methyl when applied alone and in a mixture in two agricultural soils. Biometric flasks filled with two types of soil (clay and sandy) collected from an area cultivated with sugarcane and treated with (14)C-radiolabeled solutions of the herbicides were incubated for 70 d. More (14)C-CO(2) was released when sulfometuron-methyl and hexazinone were applied in a mixture compared to when applied alone. Being used in a combination did not affect the mineralization of diuron. The soil texture directly influenced the mineralization, bound residue, and extractable residue of the three herbicides. The percentage of extractable residue decreased over time for all herbicides. Hexazinone and sulfometuron-methyl had the highest residue extracted on sandy soil when applied alone. Diuron showed the highest percentage of bound residue. The degradation of the three herbicides was higher in the clay soil regardless of the mode of application, which is related to the higher potential of the bacterial community in the clay soil to mineralize the herbicides.