Location: Soil and Water Management Research
2024 Annual Report
Objectives
Objective 1: Quantify the transport and fate of nutrients, agrochemicals, and contaminants in managed landscapes and investigate controlling mechanisms.
Sub-objective 1A: Determine the persistence and degradation of agricultural inputs and environmental contaminants and factors that control availability to biotic or abiotic (i.e., soil mineral interaction, soil temperature, moisture, and oxidation) processes.
Sub-objective 1B: Measure and model the occurrence, export, and transport of agricultural inputs and environmental contaminants to and within surface water and ground water resources.
Objective 2: Develop management approaches to reduce adverse impacts of agronomic practices on water quality and quantity.
Sub-objective 2A: Examine conventional (BAU) and aspirational (ASP) management practices and investigate new technologies and approaches that will enhance food production while protecting water resources.
Sub-objective 2B: Investigate the ecosystem services of turf.
Approach
The challenge we face with a growing world population is to increase agricultural production to meet demands while maintaining environmental quality. Critical to this challenge is protecting the integrity of water resources, which is the foundation of our project’s objectives that quantify the transport and fate of agricultural inputs and contaminants in managed landscapes (objective 1) and develop management approaches to reduce adverse impacts of agronomic practices on water quality and quantity (objective 2). Laboratory, plot level, and watershed-scale investigations will encompass one or more of three over-arching approaches that include: (1) measurements to identify occurrence of contaminants and their sources; (2) management to mitigate contaminants; and (3) modeling to evaluate broader impacts of contaminants and effectiveness of conservation practices or mitigation strategies. Research addressing the first objective will measure the persistence and degradation of agricultural inputs and environmental contaminants and factors that control their availability (subobjective 1a). This includes improving our understanding of biochar aging mechanisms that impact agrochemical sorption and degradation (goal 1a.1), and characterizing contaminants in urban agricultural systems and reducing contaminant availability with management practices (goal 1a.2). In addition, we will measure and model the occurrence, export, and transport of agricultural inputs and environmental contaminants to and within surface water and ground water resources (subobjective 1B). This includes mapping sources and sinks of contaminants in agricultural watersheds to evaluate the mitigation efficacy of management practices (goal 1b.1), and characterizing pesticide sorption to agricultural microplastics (goal 1b.2). Research addressing the second objective will examine conventional and aspirational management practices and investigate new technologies and approaches that will enhance food production while protecting water resources (subobjective 2a). This includes the evaluation of perennial and annual cover crop management practices to reduce negative impacts of row crop production on water quality (goal 2a.1), community-scale denitrifying bioreactor for mitigating nutrient and sediment losses from subsurface tile drained landscapes (goal 2a.2), and synergistic benefits of additives with optimized nitrogen management to reduce loss of soluble nitrogen from cropping systems to ground and surface waters (hypothesis 2a.3). We will also investigate the ecosystem services of turfgrass (subobjective 2b), one of the largest crops grown in the United States, to measure its effectiveness to mitigate transport of roadside contaminants to surface waters (goal 2b.1) and to evaluate the effect of soil moisture and grass species on N-cycling (goal 2b.2). Results of this research will formulate guidelines to enhance the sustainability of agriculture and protect water quality, thus improving water resource security and safeguarding the environment and human and animal health. Data from this project plan will also contribute to Long-Term Agroecosystem Research.
Progress Report
In support of Objective 1A.1, an additional two volunteers have been included in the research effort to improve understanding of biochar aging mechanisms and its impact on binding and degradation of agricultural chemicals, as well as continuing to foster connections with the Sustainable Farmers Association (SFA) in Minnesota to identify additional farmers willing to participate. Attempts were made at securing funding for larger scale field efforts through two state grant programs, but these were unsuccessful. Surface area instrumentation has been installed and calibrated to reference standards. A new collaboration with the Univ. of California-Davis has been established to explore additional facets of biochar weathering with biochar collected from their ongoing fieldplots. Additional cross-location efforts are underway within the CHARnet network (ARS) for characterization assessments and incorporation of this project’s data into the biochar selection tool being developed at the Corvallis, OR location.
In support of Objective 1A.2, scientists from St. Paul, Minnesota, collected soils in the Twin Cities metropolitan area, investigating locations of urban food production. Discussions were initiated with new collaborators aimed at soil sampling from three additional metropolitan areas in the United States and an international location. Microplastics were added to the targeted urban contaminants and extraction and analysis methodologies were confirmed with quantifying microplastics in agricultural soils where polymer coated fertilizer had been applied. Soils receiving biosolids from municipal wastewater treatment have been collected for extraction and analysis of microplastics in food production soils following contamination with known urban sources. Data processing and analysis is near completion for assessment of raised bed urban food production.
In support of Objective 1B.1, scientists from St. Paul, Minnesota, continued watershed sampling of High Island Creek through fixed-point monitoring as well as periodic paddling campaigns with a Packraft. Packraft campaigns have been limited by drought conditions during summer of 2023 as well as fewer personnel available for paddling in 2024. Monitoring data have been used to quantify preliminary nutrient loads for watershed-scale nitrate export. Spatial datasets of water quality are being used to develop new ways of thinking about watershed function. A watershed-scale model of High Island Creek has been built in the SWAT+ modeling environment and model calibration is ongoing.
Samples of agricultural plastics were collected in support of Objective 1B.2. Method evaluation and optimization continued for specialized equipment enabling pyrolysis of microplastics for identification of their plastic polymers. Photoaging of plastic for laboratory investigations was initiated. In related research supporting Objective 1B, scientists from St. Paul, Minnesota, collected stream water and atmospheric deposition for the final year of a study evaluating microplastic contamination in an undrained agricultural watershed. Extraction and analysis of samples were completed. Additionally, in collaboration with USDA-ARS Long-Term Agroecosystem Research (LTAR) network, first year sampling of ditch and tile water in drained agricultural watersheds in Minnesota, Iowa, Illinois, and Ohio was completed, sample analysis is underway, and initial data was shared in a LTAR Drainage Working Group workshop presentation.
In support of Objective 2A.1, newly established Kura clover research plots in Lamberton, Minnesota, are now in their first year of experimental treatments. Continuous flow is being monitored from tile drainage in these plots and a combination of grab samples and continuous nitrate monitoring is ongoing - with the purpose of quantifying the impact of Kura clover on water quality and quantity. Kura clover biomass data from experiments at Rosemount and Lamberton, Minnesota, have been aggregated into a data table which is being used for characterizing clover growth following a plant heat unit approach.
In support of Objective 2A.1, scientists from St. Paul, Minnesota, collected a second year of water flow and chemistry data on two paired watersheds. These data, with the previous year’s data, were graphed to show excellent pairing of tile drainage outflow and nitrogen losses from the two watersheds. The relationships (R2) were 0.96 for flow and 0.85 for nitrogen loss (1.0 being a perfect relationship). The pairings support planned nutrient management efforts of one of the watersheds.
In support of Objective 2A.2, data from the completed laboratory bioreactor experiment was finalized, and field bioreactor data were collected/vetted, and hydraulic tracer tests were conducted on the bioreactor beds.
In support of Objective 2A.3, a new multi-location field project with university collaborators was started to evaluate the impact of planting date, tillage regime, and inclusion of cover crops on soil nitrate availability, nitrous oxide emissions, and crop yields during the soybean phase of corn-soybean rotations in replicated plot experiments in Minnesota, Illinois, Kentucky and Iowa. ARS researcher in St. Paul, Minnesota, completed the first year of experiments in southeastern Minnesota. Laboratory experiments were continued using a soil microcosm incubation system to evaluate the temporal dynamics of multiple reactive nitrogen gas species (ammonia, ammonium, nitrite, nitrate, nitrous oxide, and nitric oxide). We observed unexpected production of reactive nitrogen during the incubation of plant residues from a perennial legume cover crop in the absence of soil.
Accomplishments
1. Biochar weathering is dependent on its particle size. Biochar use for removing agrochemicals from the soil has been increasing. However, the long-term impacts of biochar presence in soil are not fully known. ARS researchers in St. Paul, Minnesota conducted a study observing that the aging of the biochar in soil had differing impacts on the binding capacity of the biochar as a function of particle sizes. The smaller size fractions possessed the largest changes (decreases) in chemical binding compared to the larger particle sizes. This is an important consideration given the fact that biochar undergoes particle size reduction with tillage and soil management operations. Therefore, the effectiveness of biochar as a remediation agent for agrochemicals in soil may be greatly reduced with time, dependent on the initial particle size. These results are significant to assist farmers, scientists, and engineers as well as supplying guidance for biochar use as an agrochemical remediation tool.
2. Microplastics measured in an agricultural stream suggests watershed sources. Clean water is a valuable natural resource and basic requirement to sustain life. Microplastics (< 5 mm) are environmental contaminants of global concern with potential for adverse effects to terrestrial and aquatic ecosystems. Research has focused on marine ecosystems and urban environments, while little is known about microplastic occurrence and impact in agricultural watersheds. ARS scientists from St. Paul, Minnesota, measured quantities of microplastics in atmospheric deposition and stream outflow in an agricultural watershed. Ten times more microplastics were measured in stream water leaving the agricultural watershed than what entered in atmospheric deposition, suggesting there are sources of microplastics within the watershed. Identifying sources and routes of microplastic contamination will allow development of management strategies to reduce microplastics in water and protect water quality while maintaining agricultural productivity.
Review Publications
Felton, R., Dalzell, B.J., Baker, J.M., Flynn, K., Porter, S.A. 2023. Novel, ultralight platform for mapping water quality parameters in low-order streams. ACS Environmental Science & Technology Water. 3(10):3189-3446. https://doi.org/10.1021/acsestwater.3c00280.
Goebel, K.M., Anderson, D.E., Rice, P.J., Davros, N.M. 2024. Effects of insecticide spray drift on arthropod prey resources of birds in grasslands in Minnesota. Journal of Wildlife Management. 88(4). Article e22572. https://doi.org/10.1002/jwmg.22572.
Ippolito, J.A., Ducey, T.F., Spokas, K.A., Trippe, K.M., Johnson, M.G. 2024. A biochar selection method for remediating heavy metal contaminated mine tailings. International Journal of Environmental Science and Technology [online]. https://doi.org/10.1007/s13762-024-05621-9.
Niaz, A., Spokas, K.A., Gamiz, B., Mulla, D., Arshad, K.R., Hussain, S. 2023. 2-Methly-4-chlorophenoxyacetic acid (MPCA) sorption and desorption as a function of biochar properties and pyrolysis temperature. PLOS ONE. 18(9). Article e0291398. https://doi.org/10.1371/journal.pone.0291398.
Chou, M., Pavlou, D., Rice, P.J., Spokas, K.A., Soldat, D.J., Koch, P.L. 2024. Microbial diversity and soil health parameters associated with turfgrass landscapes. Applied Soil Ecology. 196(4). Article 105311. https://doi.org/10.1016/j.apsoil.2024.105311.