Sorption and Desorption of Diuron, Hexazinone and Mix (Diuron + Hexazinone) in Soils With Different Attributes

Abstract

In Brazil, sugarcane is grown in large areas. Weed control in sugarcane fields is done by chemical method, since it is more efficient and less expensive. In this method, herbicides that persist in the environment for long periods are used, among which there are hexazinone and diuron, which are applied in mixtures marketed by the industry. This research evaluated the sorption and desorption of hexazinone and diuron applied alone and in mixture, in two samples of Red-Yellow Latosols (LVAG and LVAV) and a Organosol (OR), with and without manure. Sorption isotherms were built using the batch equilibrium method and the identification and quantification of herbicides was obtained through a high-performance liquid chromatography (HPLC) with UV-Vis detector. There were high diuron sorption coefficients (Kf) in the soils. The hexazinone Kf values found were low in LVAG and LVAV soils, and they were high ground only in OR. In all soils, diuron and hexazinone showed higher Kf values when mixed. There was a direct relation between the addition of manure to the substrate and the Kf values . Higher desorption values (Kfd) in relation to those of sorption in LVAG and LVAV soils indicate gradual release of these herbicides in the soil solution when using organic fertilizer, showing increased sorption and desorption of these molecules; this is accentuated when they are mixed. In the Organosol, desorption was very low, and cannot be quantitated by the used method. It is possible to conclude that the incubation of LVAG and LVAV soil with manure helps both the process of sorption and desorption of herbicides. However, sorption and desorption in the Organosol is high indicating very low agrochemicals such strong bonds with soil colloids.

Influence of Soil Depth on Sorption and Desorption Processes of Hexazinone

“…Mendes et al (2019) reported that the addition of bovine bone coal to the soil increased the OC content and, consequently, the sorption of hexazinone. Therefore, the results of this study reinforce the importance of soil OC in the sorption of hexazinone, as already evidenced by Oliveira Jr. et al (2001), Pang et al (2005), and Sousa et al (2018).…”

Sorption-desorption isotherms of diuron alone and in a mixture in soils with different physico-chemical properties

“…The same authors state that the sorption variations of these herbicides when mixed may be related to soil OC quality, so that being that material of origin, decomposition and structure of the organic matter of the soil can exert different influences on the sorption of herbicides. The addition of organic compounds to the soil in the research of Sousa et al (2018) may increase the retention capacity of these herbicides when mixed, differing from the present study.…”

“…Like in the present study, soils presented a variation in the CO content between 1.0 and 2.0%, indicating that in this range the CO content of the soils had little effect on the sorption of the diuron alone and in the mixture. However, for diuron alone, Giori et al (2014) found a correlation between herbicide sorption and soil OC (0.76-2.6%), as well as Sousa et al (2018), who verified a correlation of diuron sorption both alone and in mixture with hexazinone, considering a greater range of OC (1.46-27.77%). This indicates that the type of organic material present in the soil can alter the retention dynamics of the herbicides in the soil, whether isolated or mixed.…”

“…On the other hand, Sousa et al (2018), studying the sorption of the diuron alone and in combination with the hexazinone, found that the mixture had on average twice the sorption with respect to the diuron alone. The same authors state that the sorption variations of these herbicides when mixed may be related to soil OC quality, so that being that material of origin, decomposition and structure of the organic matter of the soil can exert different influences on the sorption of herbicides.…”

“…Inoue et al (2008) found low mobility for the isolated diuron (precipitation up to 40 mm), which was associated with the highest clay content (56%) and low OC (1.6%). However, the application of diuron in a mixture may exhibit distinct behavior in the soil when compared with the isolated molecule (Sousa et al, 2018).…”