Characterizing atrazine, mesosulfuron-methyl, and topramezone bioavailability in North Carolina soils using greenhouse bioassays

Authors: Ramanathan, Shwetha; GANNON, TRAVIS - North Carolina State University; Locke, Anna; EVERMAN, WESLEY - North Carolina State University

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2023
Publication Date: 5/9/2023
Citation: Ramanathan, S., Gannon, T., Locke, A.M., Everman, W. 2023. Characterizing atrazine, mesosulfuron-methyl, and topramezone bioavailability in North Carolina soils using greenhouse bioassays. Agrosystems, Geosciences & Environment. https://doi.org/10.1002/agg2.20371.
DOI: https://doi.org/10.1002/agg2.20371

Interpretive Summary: The ease with which herbicide molecules in the soil can be absorbed by plants is called bioavailability. Soil properties can affect how tightly herbicide molecules bind to soil particles, thus affecting the bioavailability of the herbicide to plants. Along with other properties such as herbicide degradation time, the bioavailability of herbicide determines the potential for herbicide to damage a crop long after it was applied. To assess bioavailability, we measured plant injury from a range of herbicide concentrations in three different soil types. These measurements were made for soybean, an important crop, along with other plant species that are known to be very sensitive to herbicide. Herbicide bioavailability varied among the different soil types. Thus, soil type should be taken into consideration when planning herbicide applications.

Technical Abstract: Herbicide carryover injury to rotational crops can vary in severity depending on the influence of soil properties on herbicide bioavailability. Greenhouse bioassays were conducted with soybean, radish, and canola to evaluate differences in the bioavailability of three herbicides with carryover-risk, viz., atrazine, mesosulfuron-methyl, and topramezone, in three regional soil types representing different textures and properties. Plant visual injury was evaluated weekly, and weights of aboveground dry plant biomass were recorded after harvest of soybean 28 d after emergence (DAE) and radish and canola 21 DAE. Nonlinear regression and log-logistic dose-response models were used to quantify herbicide effective concentrations for 30% (EC30), 50% (EC50), and 80% (EC80) visual injury and aboveground dry biomass reduction in each soil type. Relative herbicide-soil bioavailability was determined through comparisons of herbicide effective concentrations across soil types. Pearson’s correlation revealed that atrazine, mesosulfuron-methyl, and topramezone EC30 estimates for responses in soybean and radish or canola were positively correlated to soil organic matter (OM) content (r = 0.56, 0.48, and 0.40, respectively) and cation exchange capacity (CEC) (r = 0.43, 0.41, and 0.45). Topramezone EC80 for responses in soybean and radish was positively correlated to soil clay content (r = 0.51) and silt content (r = 0.51) and negatively correlated to sand content (r = -0.51) and pH (r = -0.52). The potential for rotational crop injury from carryover of atrazine, mesosulfuron-methyl, and topramezone in regional soil types can be identified based on the influence of their specific properties on herbicide bioavailability.