Sorption of diuron and sulfentrazone on different substrates

The efficiency in pre-emergence weed control is linked to the understanding of sorption, whose process makes the herbicide molecule unavailable for absorption by plants, and only returns to the soil solution after desorption processes. Understanding herbicide sorption is crucial, especially when separating the use of substrates as a fixation base for plants, which can absorb greater or lesser amount of applied herbicides. Therefore, this study aimed to quantify the sorption of diuron and sulfentrazone herbicides on different substrates. Two experiments were carried out, the first was the control experiment, using washed sand substrate as control for the application of seven doses of the two proposed herbicides. In the second experiment, six doses of both herbicides were tested on six different substrates. The treatments were conducted in a greenhouse using polyethylene pots and cucumber with indicator plant. The characteristics evaluated were the determination of the I50 value of the test plant for each substrate as a function of the doses of each herbicide and the estimation of the amount of diuron and sulfentrazone sorbed in each substrate. Indian Black Earth showed the highest sorption capacity for diuron and sulfentrazone, followed by coconut fiber. The diuron doses for Indian Black Earth and Sand + Indian Black Earth were not effective in controlling the plant population. The substrates mixed with sand showed lower sorption capacity than the others, requiring greater care when using herbicides. The organic matter, pH and soil texture are factors that contributed to the sorption of herbicides.