Location: Agroecosystems Management Research
2024 Annual Report
Objectives
Objective 1: Evaluate trends in hydrology and water quality in agricultural watersheds managed with current production practices. The research utilizes georeferenced data relating to landuse, terrain, cropping and animal production, observable use of conservation practices, and climate and meteorological data.
1.A: Document changes in land use, conservation practices, and climate as drivers of water quality trends in three Iowa watersheds.
1.B: Utilize new stream monitoring technology and terrain analyses to document stream bank movement and water quality changes along the SFIR, as related to adjacent land use and extreme weather events.
Objective 2: In collaboration with other Long-Term Agroecosystem Research (LTAR) network sites, identify practices and factors that influence the effectiveness of conservation practices.
2.A: Compare the effects of ASP cropping system as part of the LTAR Common Experiment with other C-S cropping systems on targets such as N loss to drainage.
2.B: Determine crop water use using UAV imagery.
Objective 3: Assess and improve models and remote sensing to characterize fields and watersheds.
3.A: Assess and improve modeling of Midwest conservation practices for sustainable intensification of agriculture.
3.B: Assess and improve mapping and analysis of subsurface drainage (e.g., patterns and intensity) using techniques from UAS and satellite imagery from several Midwest locations including four LTAR-drainage workgroup sites (Ames, St. Paul, W. Lafayette, Columbus).
Approach
This project will investigate the effects of agricultural management practices at field and watershed scales, investigate the dynamics of watershed hydrology, and assess and improve tools to characterize agricultural systems.
Under the first objective, watershed studies will evaluate practices that can reduce loss of nitrate-nitrogen and phosphorous from cropped fields. These practices include saturated buffers, bioreactors, and blind surface inlets to subsurface drainage. Trend analysis will be conducted on long term records in the watershed studies to gain insight on water quality and streamflow variability over time. Streambank movement in these watersheds will be monitored with remote sensing.
Under the second objective, field studies will be conducted as part of the Long-Term Agroecosystem Research network that will support research to sustain or enhance agricultural production and environmental quality in the Upper Mississippi River Basin (UMRB) region.
The third objective will employ a mix of modeling and remote sensing studies to evaluate conservation practices and subsurface drainage systems.
A breadth of watershed monitoring, remote sensing, controlled experiments in field and laboratory, and modeling techniques will be employed in the research. Publications, tools for conservation planning, and databases available to other scientists will be produced. Results are intended to enable agriculture to better manage water resources for multiple needs; particularly, in the UMRB.
Progress Report
In support of Objective 1, ongoing collection of hydrologic and water quality data was obtained from the experimental watersheds, with laboratory measurements completed for the 2023 sampling season. Sampling and analysis for the 2024 year are underway. The data from these watersheds were added to the “Sustaining the
Earth's Watersheds, Agricultural Research Data System” database, which supports both the Conservation Effects Assessment Project (CEAP) and the Long-Term Agroecosystem Research (LTAR) network. Also related to Objective 1, there were delays in hiring a Southfork Watershed Alliance (SFWA) coordinator, which affected plans for the installation of six new saturated buffers as part of Batch and Build effort in the South Fork Watershed. The Batch and Build model, initially implemented by the Conservation Infrastructure initiative in 2021, aimed to significantly scale up the number of saturated buffers and bioreactors in Iowa. Despite these delays, progress related to the installation of these new saturated sites was significant during the current year. For example, land surveillance for all six proposed sites was completed and environmental engineering firms are currently designing blueprints. Additionally, deep soil cores from the proposed sites were taken and analyzed as part of the suitability evaluation. To take full advantage of the SFWA Batch and Build approach, which covers the cost of land survey, design, and installation of about 20 new edge-of-field practices (including six of ARS sites), the completion of work depends on the overall progress led by SFWA. Furthermore, ongoing work on existing saturated buffers continues, with water samples collected on a biweekly basis and analyzed for nitrates. To enhance our understanding of the buffer effect on nitrate reduction, we submitted a manuscript titled “Calibration of V-notch and compound weirs for drainage water level control structures” to the journal Applied Engineering in Agriculture. This research focuses on calibrating subsurface drainage flow and nitrate measurements. Additionally, we conducted four Unmanned Aerial System (UAS) Light Detection and Ranging (LiDAR) mapping surveys along sites in the South Fork Iowa River reach areas, adjacent to existing stream flow monitoring stations. These missions took place from Fall 2022 to Spring 2024 and aimed to document stream bank migration and retreat due to erosion. Our preliminary analysis highlights several locations along the area of interest that have experienced bank migration, indicating the presence of secondary flow currents common in flashy drainage systems during high flows. Furthermore, we established partnerships with ARS locations in Missouri, Oklahoma, and Mississippi to analyze climate and discharge data collected from four LTAR/CEAP watersheds within the Mississippi River Basin. The primary objective of this research was to determine whether long-term climate and river/stream discharge trends align with predictions from Global Climate Models (GCMs). Our initial findings from these collaborative efforts were presented at the 2023 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America International Annual Meeting, under the title “Climate and Discharge Trends in Mississippi River Basin LTAR Watersheds." Currently, we are working on a peer-reviewed manuscript that will present analysis of multi-location trends in long-term records (over 50 years) of precipitation, temperature, and discharge. Preliminary results indicate consistency with predictions from the GCMs.
In support of Objective 2, drainage water samples from the Kelley field site near Ames, Iowa, are being collected and analyzed as part of LTAR efforts to quantify the effect of cropping systems, conservation practices and nitrogen (N) management on water quality and nitrous oxide emissions. All 24 plots are now equipped with nitrate sensors which allow us to monitor rapid changes in tile drainage nitrate concentrations on an hourly basis. Nitrous oxide emissions are being monitored weekly. Nitrate, phosphorus (P), sulfur, and potassium (K) losses in tile drainage are being measured weekly during flow events. Conservation practices, such as implementation of annual rye cover crop and in-situ woodchip denitrification bioreactors, were shown to significantly reduce nitrate loss due to leaching relative to conventional practices over the study period. Specifically, corn and soybean managed under no-till with rye cover crop and no-till with in-situ woodchip denitrification wall reduced N loss 59 and 58% compared with conventional practices. Cropping system had no significant effect on concentration of orthophosphate, total P, or sulfur in the drainage. In-situ woodchip bioreactors leached more K than similarly managed no-till plots, presumably due to decomposing wood serving as an additional source of K. Biological degradation promotes K movement and leaching over prolonged periods of time, especially for woody biomass, such as oak woodchips used in our study. Therefore, increased K leaching from bioreactors was most likely a result of K loss from decomposing woodchips and in-situ bioreactors did not impact K availability to plants. Moreover, no specific environmental issues arise from K leaching.
In support of Objective 3, data is continuing to be gathered from the Kelley field site near Ames, Iowa, to parameterize and test the SWAT model to simulate the effect of winter cover crops on N loss to drainage. Model simulations match reasonably well with field observations of N loss to drainage and crop growth. For example, with the cover crop treatment the average annual 2002-2010 observed and simulated drainage amount was 35.9 and 31.8 cm and annual drainage N loss was 20.8 and 23.4 kg N/ha. In comparison, the no cover crop treatment observed and simulated N loss in drainage were 49.3 and 49.8 kg N/ha. We provided this calibrated SWAT model to the LTAR-modeling working group that is testing aspirational/alternative practices across several LTAR sites. Alternative practices for Ames in this context include winter rye cover crop harvested as a bioenergy feedstock. Additional progress in modeling of Midwest conservation practices for sustainable intensification of agriculture includes a draft journal article in review by coauthors titled “Modeling integrated crop- livestock system (ICLS) in the monoculture production system of the U.S. Midwest: a system-of-systems approach." A main finding of this research is that the environmental and economically optimal production system is the combination of ICLS and cover crops. In addition, UAS flights have continued at the Kelley field site to help identify subsurface drainpipe configurations. Several flights have been completed. While techniques have been modified to increase the quality of the products, field drainpipes have not been detected. To increase the chances of detecting drainpipes, we have partnered with other locations to investigate this drainpipe detection method (e.g., ARS researchers at Saint Paul, Minnesota, and Purdue University faculty). With continued monitoring, drainpipes are expected to be detected when conditions are more favorable (e.g., soil type, soil water content, drainage rate, and surface crop residue and growth stage). However, the most favorable conditions are not yet fully understood. A methodological framework is being developed to determine optimal conditions for drainpipe detection in the U.S. Midwest.
Accomplishments
1. Long-term conservation practices reduce nitrate leaching while maintaining yields in tile-drained Midwestern soils. Nitrate losses from drained Midwestern corn-soybean systems to the Mississippi River is a leading contributor to hypoxia or the “dead zone” in the Gulf of Mexico. Conservation practices such as cover crops and woodchip bioreactors can reduce these nitrate losses and improve water quality. However, the long- term performance of these practices has not been sufficiently quantified. ARS scientists in Ames, Iowa, in collaboration with Iowa State University, analyzed 19 years of data suggesting that higher annual precipitation resulted in increased effectiveness of an in-situ woodchip bioreactor, while effectiveness of rye cover crop increased in dry years. Overall, both the rye crop and in-situ bioreactors reduced nitrogen (N) leaching by nearly 60% compared with the prevailing business as usual corn-soybean system. Notably, the effectiveness of in-situ woodchip bioreactors did not diminish over the study period highlighting its long-term viability. Minimal or no yield penalty was observed following adoption of these conservation practices, which is important for their wider acceptance by the agriculture community. This research will help in the efforts to design and implement effective management systems to reduce N loads to the Mississippi River Basin and Gulf of Mexico while maintaining crop production.
2. Conservation practices that promote soil health increase water storage, enhance yields and resilience and reduce greenhouse gas emissions. Soil health plays a critical role in sustaining ecosystems, enhancing crop production, and supporting diverse biological functions. ARS scientists in Ames, Iowa, in collaboration with The Nature Conservancy, Iowa State University, Ohio State University, and the University of Illinois, published a paper that synthesized a collection of long-term data within agricultural systems and proposed an integrated approach to better quantify and understand soil health dynamics. The paper, which received the 2024 Borlaug Communication Award, underscored longstanding soil and water conservation practices like no-tillage and using cover crops to improve soil health, emphasizing their benefits, such as increased water storage, enhanced crop yields and resilience, and reduced greenhouse gas emissions. Importantly, the paper aimed to fill a crucial knowledge gap by focusing on the impacts of soil health practices on the hydrologic cycle. It seeks to provide a detailed analysis of how these practices affect water movement within ecosystems and offer evidence- based recommendations for policymakers and decision-makers on incorporating soil health improvements into agricultural and environmental strategies.
Review Publications
Rogovska, N.P., O'Brien, P.L., Malone, R.W., Emmett, B.D., Kovar, J.L., Jaynes, D., Kaspar, T., Moorman, T., Kyveryga, P. 2023. Long-term conservation practices reduce nitrate leaching while maintaining yields in tile-drained Midwestern soils. Agricultural Water Management. 288. Article e108481. https://doi.org/10.1016/j.agwat.2023.108481.
Johnson, G., Christianson, L., Christianson, R., Davis, M., Diaz-Garcia, C., Groh, T., Isenhart, T., Kjaersgaard, J., Malone, R.W., Pease, L., Rogovska, N.P. 2023. Effectiveness of saturated buffers on water pollutant reduction from agricultural drainage. Journal of the ASABE. 1(1): 49-62. https://doi.org/10.13031/jnrae.15516.
Liang, K., Qi, J., Zhang, X., Emmett, B.D., Johnson, J.M., Malone, R.W., Moglen, G.E., Venterea, R.T. 2023. Nitrous oxide emissions from multiple agroecosystems in the U.S. Corn Belt simulated using the modified SWAT-C model . Environmental Pollution. 337(2023). Article e122537. https://doi.org/10.1016/j.envpol.2023.122537.
Koehn, A.C., Bjorneberg, D.L., Ma, L., Leytem, A.B., Malone, R.W., Nouwakpo, S.K., Qi, Z. 2024. Climate change in a semi-arid environment: Effects on crop rotation with dairy manure applications. Journal of the ASABE. 66(6):1449-1468. https://doi.org/https://doi.org/10.13031/ja.15661.
Sauer, T.J., Wacha, K.M., Brevik, E.C., Zamora, D. 2023. Eastern red cedar effects on carbon sequestration and soil quality in the great plains. Soil Science Society of America Journal. https://doi.org/10.1002/saj2.20534.
Wyatt, B., Hatfield, J.L., Wacha, K.M., Lal, R., Arenas, A., Birge, H., Schnitkey, G.D., Peterson, T. 2024. Soil health and the hydrologic cycle. Council for Agricultural Science and Technology Issue Paper. 76. https://doi.org/10.62300/QEOG5785.