Soil Mobility and Residual Effects of Herbicides Applied on Corn Straw

The efficacy of herbicides is directly related to its availability in biological targets. The presence of straw cover on the soil, coupled with dry period conditions following pre-emergence herbicide application, has raised concerns regarding pre-emergence herbicide efficacy, mainly because of the increased potential for herbicide retention and degradation. This research aimed to elucidate how different levels of corn straw and dry periods impact the mobility and residual activity of key pre-emergence herbicides used in cultivation systems with soil coverage. The results showed that diclosulam and sulfentrazone maintained their mobility and efficacy in controlling <i>Commelina benghalensis</i> L., regardless of straw cover or dry periods. However, the residual activity of diclosulam was slightly reduced by straw, while sulfentrazone remained effective 42 days after herbicide application. In contrast, the presence of straw negatively affected the mobility and efficacy of flumioxazin and S-metolachlor, reducing their effectiveness in controlling <i>C. benghalensis</i> L, regardless of dry periods. The residual activity was also negatively affected by straw on the soil, particularly in the case of flumioxazin. Herbicides with greater stability under straw and dry conditions, such as diclosulam and sulfentrazone, exhibit more consistent performance, while flumioxazin and S-metolachlor molecules require complementary management strategies to maintain efficacy. Thus, farmers should consider the amount of straw on the soil and the possibility of dry periods when selecting pre-emergence herbicides. From an environmental perspective, the distinct physicochemical properties of the evaluated herbicides determine their mobility, persistence, and potential risk of contamination through leaching and surface runoff. Understanding these interations supports the development of integrated weed management and environmental protection strategies in agricultural systems conservation.