Significance:

Nanosized agrochemicals are a new approach in an effort to improve efficiency, enhance stability, prolong treatment duration, and reduce environmental implications in agricultural ecosystems for common pests. Nanopesticides, specifically nano-copper (Cu) fungicides have recently been introduced in place of traditional copper(II) sulfate (CuSO4). Nano-Cu fungicides has been found to effectively increase leaf foilage, particularly in highly fertilized fields. Over 4 million pounds of  copper based fungicides are applied annually to agricultural soils in the United States, some of which are present in nano-formulations. Copper based fungicides are used for growing vegetables, fruit, orchards, and grapes to treat fungal diseases (e.g., blight, black spot, dowy mildew). Implications of nano-Cu fungicides on human and soil health along with nutrient removal processes is only starting to be considered. Recent discoveries of negative influences of nano-Cu fungicides, specifically Cu(OH)2, on bacterial denitrification (one the most important nitrogen removal pathways in agroecosystems)11, the carbon cycle1, and biodegradation of neonicotinoid insecticides10features the urgency for an improved understanding of these nanomaterials in realistic field settings. Further, the persistence, transport, degradation, and physiological responses of microbes to these engineered nanomaterials is currently only being explored exclusively, to our knowledge, at the laboratory setting.

Objectives:

RO1: Complete coupled microcosm/mesocosm scale experiments to assess microbial alterations and neonicotinoid insecticide degradation based on varying nanopesticide application and recurrance rates;

RO2: Conduct a 2 year field study to assess nanopesticide pesistance, fate, and transport;

RO3: Create kinetic models from bench, mesocosm, and field scale experiments and incorporate findings into HYDRUS modeling software to predict fate and transport of nanopesticides into the vadose zone;

Hypothesis:

Nano-Cu fungicides will alter the microbial community and functionality in agricultural soils and limit degradation of neonicotinoid insecticides and transport and/or persistence of nano-Cu fungicides will result in limited denitrification in downstream best management practices (e.g., riparian wetlands).

Conclusions:

RO1: Microcosm

1.Following potential nitrification incubations (aerobic conversion of NH4 to NO2) differences were not observed between soil sources (wetland vs. field plot) or pesticide treatment.

2.In contrast, the following observations were made for the potential denitrification incubations(anaerobic conversion of NO3 to NO2  to N2)

•Wetland sediment had a higher denitrification rates compared to the field plot soil.

•Lower denitrification rates were observed during week 5 indicating a potential microbial shift.

•Highest copper hydroxide and pesticide mixes that included copper hydroxide and imidacloprid reduced denitrification activity.

RO1: Mesocosm

1.Imidacloprid decreased through time in the water column.

2.Copper was removed through plant uptake and sedimentation.

3.Pesticide application did not affect the growth and survival of wetlands.

4.Pesticide applications inhibited N uptake in below ground biomass.

5.Pesticide applications decreased phosphate-P loss from wetland soils.

RO2: Field Plots

1.Imidacloprid loss at the field plots was primarily observed in runoff from the storm immediately following application.

2.Phosphate-P and Total Nitrogen in runoff were significantly higher in copper treatments during the 2022 growing season.

3.Copper concentrations were significantly higher in soils at the end of the growing season in copper hydroxide plots.

RO3: Modeling

Application of pesticides increased nitrate-N removal rates in wetland systems.

Funded: USDA-NIFA

Publications: In-Prep

Graduate Student:

Jacob Richardson (MS)
William Rud (MS)
Caleb Stickney (MS)
Kiley Powers (MS)