Doctor of Philosophy (PhD)


Environmental Science

Document Type



Synthetic herbicides, with their varying modes of action, are well known for their efficiency in the suppression and control of weed species in U.S. agriculture. However, the consequences of using synthetic herbicides without attention to the surrounding environment can produce chemical run-off, changes in soil health and soil health conditions, and create herbicide-resistant weeds. These consequences have encouraged growers to find alternatives in their weed management programs. In this study, organic and synthetic herbicides were assessed on how well they performed in weed suppression surveys, and their potential effects on soil health indicators. Commonly used indicators include soil pH, β-glucosidase activity, electrical conductivity, total nitrogen and carbon, total FAMES, and soil respiration. These measurements were taken at two different locations and two different soil types. Experimental research plots were placed on a midland silty clay loam in 2021 and an additional acadiana silt loam experimental research plot was added in 2022. Results showed organic herbicides did not significantly affect soil health parameters, but were not comparable to synthetic herbicides in weed suppression. Even when ideal conditions and treatment parameters were met, this did not improve weed suppression and control with these natural herbicides. When evaluating microbial communities and soil respiration, the type of treatment (synthetic or organic) applied was not significant to a microbial population as a whole, but that their concentrations and specific groups could be affected in the short-term. Overall, it is inferred that synthetic herbicides do not negatively affect soil conditions in the long-term, as is commonly assumed. In weed management programs, using recommended herbicide application rates outlined on the herbicide label, and conducting applications with environmental stewardship in mind, could decrease possible herbicide effects on non-target organisms within the environment.



Committee Chair

Hou, Aixin

Available for download on Tuesday, August 27, 2024