Thiamethoxam and clothianidin are two neonicotinoids used in seed coatings for crops such as corn and soybeans. Both neonicotinoids have high solubility in water, so they are prone to transport via leaching and runoff. This thesis is comprised of two studies that evaluated potential solutions to mitigate neonicotinoid transport from fields. The first study examined the relationship between soil organic carbon content and neonicotinoid transport in a field planted in soybeans. Soils with increased organic carbon leached less thiamethoxam and clothianidin during early growing season leaching peaks; however, at the end of the season, higher organic carbon content only decreased leached mass of clothianidin. The second study was to determine neonicotinoid uptake of different ground covers used as cover crops or edge-of-field buffer strips, as well as the partitioning of thiamethoxam and clothianidin throughout the plants. Ground covers, such as crimson clover, had the highest recovery of applied thiamethoxam, meaning that it may be a good candidate to retain this pesticide in fields. Thiamethoxam and clothianidin concentrations were higher in leaf tissues than in stems or roots, indicating that above-ground biomass removal may be an effective way to reduce neonicotinoid loading in the environment. From these studies, I concluded 1) practices that raise the amount of organic carbon in the soil may help decrease early-season neonicotinoid transport, resulting in lower concentrations in surrounding waterways, and 2) careful selection of plant species, such as crimson clover, may help reduce neonicotinoid transport in the environment, while potentially reducing exposure to beneficial insects. / Master of Science / Pesticides called neonicotinoids are commonly applied to seeds in row crops, such as corn and soybeans, before they are planted. These pesticides are highly soluble in water, which can lead to them exiting fields through runoff or leaching. This thesis is comprised of two studies that examined several potential solutions for decreasing the amount of neonicotinoids available for transport. The first study examined the relationship between organic carbon in the soil and neonicotinoids, and whether this relationship helps to retain neonicotinoids in a soybean field. Soils with high organic carbon content decreased the amount of neonicotinoids exiting the field during early growing season storms; however, at the end of the season, high organic carbon content only decreased losses for one of the pesticides studied. The second study was to determine which of six plant species and two mixes used as cover crops or buffers were the most effective at removing neonicotinoids from soil, as well as where in the plant these neonicotinoids go after uptake. Ground covers, such as crimson clover, had the highest recovery of applied neonicotinoids, meaning they would be good candidates for planting around fields. Ultimately, neonicotinoid accumulation was higher in leaves than in stems or roots, meaning that removing and disposing of leaves in an environmentally safe way could be an effective way to decrease neonicotinoid pollution. From these two studies, I found that 1) increasing organic matter in the soil can stop neonicotinoids from exiting the area it was applied in, and 2) careful consideration of plant species in or around the field may help intercept neonicotinoids before they exit the field.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/101049 |
| Date | 08 December 2020 |
| Creators | Morrison, Benjamin Anthony |
| Contributors | Crop and Soil Environmental Sciences, Stewart, Ryan D., Xia, Kang, Thompson, Thomas L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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