Soil pH Interference in the Behavior of Weak Acid Herbicides

Herbicides derived from weak acids, when suffering interactions with soil pH, can be affected in their sorptive capacity. In this way, when they suffer increased pH, they can reduce their sorption in the soil and increase their leaching. This allows the herbicide to have a higher bioavailability in the soil, generating a greater control effect on weeds and injuries in crops. Nevertheless, if there was rainfall, the herbicide may be transported by leaching in the soil profile to the deeper layers of the active seed bank, consequently, negatively impacts weed control. In view of the above, it is important to study the interactions with soil pH in the procedures of risk assessment and agronomic efficacy to obtain an analysis of the behavior that the herbicide can present in the soil, and the correct positioning of the product in chemical management. This chapter shows how the pH of the soil can interfere with the behavior of weak acidic herbicides in a chemically understandable way for professionals in the agrarian sciences. The difference between the electric charges of ionized herbicides and colloids was fundamental to understand how these interactions occur, influenced by the type and pH of the soil. Finally, it is expected that professionals who work with herbicides can better understand some of the interactions of the chemical molecules of the herbicides with the soil and make an appropriate recommendation of the products to increase the effectiveness of weed control.