COS 70-3 - Determining the effect of agricultural chemicals on native plants of the Dakotas

Abstract: Agricultural chemicals (agrochemicals) are nearly ubiquitous on the Dakota landscape. Over 22 million pounds of herbicide were applied to corn fields alone in North and South Dakota in 2021. These agrochemicals can drift from the target field of application to non-target lands, such as grasslands. Historically, the Dakotas contained nearly contiguous grasslands; however, due to conversion to agriculture, few of these lands remain untouched. Compared to historic coverage, an estimated 71.9-99.9% of North and South Dakota grassland has been lost due to land use change. The remaining grassland is fragmented into small patches embedded in an agricultural matrix. Agrochemicals have been observed to have negative impacts on non-target plant communities, even at small doses such as those observed in drift. Drift of agrochemicals may affect the success of establishment when using seed-based restoration on land in an agricultural matrix.

Our objective was to evaluate if native seedling emergence and growth are affected by agricultural chemical presence at different concentrations. We studied the effect of three common agricultural herbicides (atrazine, trifluralin, and 2,4-D) on the emergence and growth of fourteen native plant species of the Dakotas. For each chemical, we used 5 concentrations with 10 replicates of 1 seedling. The different concentrations of herbicide were intended to simulate the range of herbicide that a native seed adjacent to agricultural lands may be exposed to. We hypothesized that seedling emergence, leaf count, height, and dry biomass would decrease as chemical concentration increases. Our results show that these agrochemicals can negatively affect certain native plant species' emergence and growth at a wide range of concentrations. For example, dry biomass for thirteen out of the fourteen study species was negatively affected with exposure to a range of atrazine concentrations. Elucidating species-specific response to agrochemicals will improve restoration outcomes where drift is likely. This information will be used to inform land managers and restoration practitioners of recommended species to use in restoration adjacent to crop fields to increase the success of seed-based restoration efforts.