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.

The use of agrochemicals, like neonicotinoid insecticides can threaten human and environmental health when they are transported from agricultural fields. To minimize environmental impact of neonicotinoid pesticides to non-target organisms, it is important to quantify the movement of neonicotinoids from agricultural fields and examine how conventional agricultural practices can be altered using best management practices to minimize neonicotinoid transport. We developed a proportional runoff sampler that is inexpensive, rugged, and adaptable to existing runoff quantification systems. The sampler accurately collected flow-weighted samples under a broad range of steady-state and variable flow conditions. We then incorporated the sampler, along with leachate and soil sampling techniques, in a two-year field study testing the effects of winter cover crops and different edge-of-field buffer strip plant types on movement of the neonicotinoid thiamethoxam (TMX) and its metabolite clothianidin (CLO) in treated agricultural fields. Due to dry weather and other complications, runoff and leachate data could not be statistically analyzed. Soil samples indicated that cover crops had no effect on insecticide retention, so cover crops may not be a viable strategy to prevent neonicotinoid transport. Soil TMX was higher in grass buffers than native forb buffers in 2020; however, this result was not repeated in 2021 when vegetative cover was more consistent across treatments. CLO concentration did not vary by buffer in either year. Therefore, buffer strip plant type may have less impact on TMX and CLO retention than other factors like plant density. / Master of Science / Since the 1950's high yield crops and the use of pesticides and fertilizers have helped farmers increase yields from agricultural land. Increased yields have helped food production keep pace with population growth, but the use of pesticides and fertilizers can pose a threat to human and environmental health. Neonicotinoid insecticides can kill not only agricultural pests but beneficial invertebrates like bees and butterflies when the pesticides leave agricultural fields. To lessen environmental impact of neonicotinoid pesticides to the environment, it is important to understand 1) how these insecticides move from agricultural fields, and 2) how conventional agricultural practices can be altered to minimize neonicotinoid transport. We first developed a runoff sampler that was inexpensive, low maintenance, and adaptable to existing systems used to measure runoff. The sampler collects water at a rate proportional to the runoff rate under constant and changing flow rates. We then used the sampler along with leachate and soil sampling techniques in a field study testing the effect of winter cover crops and the species planted in edge-of-field vegetated buffer strips on the amount of the neonicotinoid thiamethoxam (TMX) and its degradation product clothianidin (CLO) remaining in the soil of treated fields during two growing seasons. Due to dry weather and other complications, runoff and leachate data could not be statistically analyzed. Cover crops did not change soil pesticide concentration either year, so cover crops may not be a viable strategy for preventing neonicotinoid transport. Soil TMX was higher in grass buffers than native forb buffers in 2020; however, this result was not detected in 2021 when plant growth in buffers was more uniform across treatments. CLO concentration did not vary by buffer type in either year. Therefore, the species planted in buffer strips may not be as important to holding TMX and CLO in soils as other factors like plant density.

Le colture energetiche su larga scala, cosi come l’utilizzo di biomassa forestale non residuale, impattano notevolvente i cicli di nutrienti, la biodiversità e l’occupazione di suolo (i tre limiti del pianeta già oltrepassati, oltre al cambiamento climatico) risultando non riconciliabili con uno spazio di operazione sicuro per l’umanità. Occorre piuttosto perseguire fonti di energia rinnovabile che consentano di disaccoppiare il sistema energetico dall’emissione di gas climalteranti ed al contempo richiedano un uso minimo del suolo e limitati impatti sui cicli dei nutrienti e sulla biodiversità.La biomassa forestale residua, la biomassa coltivata in terreni marginali / abbandonati con un basso apporto di nutrienti e la biomass residual proveniente da altri settori dell'economia possono fornire una fonte temporanea di energia per quei settori più difficili da dissociare dai combustibili fossili, in un percorso che porti verso una società in meno dipendente dalle tecnologie di combustione. / Large scale dedicated cultivation of bioenergy on fertile arable land or the large scale deployment of biomass from standing forest, with their impact on nutrient cycles, biodiversity and land occupation (the three planet boundaries which are already overtaken beside climate change) is difficult to reconcile with a safe operating space for humanity. Renewable energy sources allowing the decoupling of energy systems from GHG emission requiring a minimal land use, and therefore limited impacts on nutrient cycles and biodiversity, are to be pursued. Residual biomass such as forest harvest residues, biomass cultivated in marginal/abandoned land with low nutrients input, and biowaste from other sectors of the economy may provide a temporary source of energy for those sectors more difficult to decouple from fossil fuels, towards a society less dependent on combustion technologies.