Agricultural soils in the Chesapeake Bay region are often rich in nutrients such as phosphate. However, some forms of phosphate are bound to iron in soils and are not available for plant uptake (McQueen et al. 1986). As a result of saltwater intrusion (SWI), or the underground movement of ocean water to inland areas, coastal farmland around the region has begun to transition to wetland habitat. This has caused shifts in the dominant pools of iron found in the soils along these transitional zones (Tully et al. 2019; Williams et al. 2014). The changing structure of iron from crystalline to amorphous and dissolved forms can release phosphate from soils and allow it to wash farther downstream with outgoing tides. The resulting excess of phosphorus in the water can lead to nutrient pollution problems. Therefore, the underlying chemical mechanisms that mediate interactions between saltwater and iron in coastal soils is important to study.
Dani and I spent the summer and into the fall semester simulating SWI on a farm soil in the lab. First, we collected agricultural soil from an actively farmed field on the Eastern Shore of Maryland. Then we weighed it into separate beakers and treated it with eight different combinations of ions found in saltwater. We set the treatments to 15ppt to simulate brackish water intruding onto an agricultural field. We purged half of the microcosms with nitrogen gas and sealed them off to simulate anaerobic conditions as agricultural soils transition to wetlands. The other half were left open to the air. Then, we extracted total dissolved iron from water and total and amorphous iron from soil sampled from the microcosms at 0, 15 and 30 days. We finished the iron extractions last week and have run two of three sets of extractions on the Flame Atomic Absorption Spectroscopy (AAS). One more to go!
Our initial plan was to finish the analysis by the end of September. However, due to some serious technical issues, we could not run our samples until October. Although encountering technical problems was not a pleasant experience, the troubleshooting process improved my problem-solving skills and enhanced my conceptual understanding of the AAS. Furthermore, discussing AAS methods with Dani was rewarding. I not only enhanced my analytical skills but learned the importance of choosing appropriate methods for analyzing samples in order to collect reliable data.
We are currently in the process of analyzing the data, and I am looking forward to our results. I hope that our work will help others understand the effects of SWI on iron transformations in coastal soils. This research could lead to improved environmental policies on agricultural land affected by SWI.
McQueen D.J., Lean D.R.S. & Charlton, M.N. (1986), The effects of hypolimnetic aeration on iron-phosphorus interaction. Water Res. 20:1129-1135.
Tully, K.L., Weissman, D., Wyner, W.J., Miller, J. & Jordan, T. (2019). Soils in transition: saltwater intrusion alters soil chemistry in agricultural fields. Biogeochemistry. 142:339-356, DOI: 10.1007/s10533-019-00538-9
Williams, A.A., Lauer, N.T. & Hackney, C.T. (2014). Soil Phosphorus Dynamics and Saltwater Intrusion in a Florida Estuary. Wetlands, 34:535-544. DOI: 10.1007/s13157-014-0520-7
- By Tia Ouyang
Check out the latest AgroEcoLab publication in Agronomy Journal!
You can read it online here!
When I first told my mom what I would be doing for work this summer, she seemed just as excited as I was. After telling her I would be spending some of my days in the field collecting soil samples, she quickly went on Amazon and insisted that she should order me a bucket hat with bug netting. While I had other thoughts at the time, I have never been more grateful for such a goofy looking (yet practical) hat.
So far, my bucket hat has come along with me to more than 20 different farm fields in Somerset County, MD, protecting me from the sun and bugs while I collected my samples. Somerset County is very low elevation (2 ft above sea level in many cases), and with climate change and sea level rise, saltwater water is encroaching on crop fields all along the county’s shores (known as saltwater intrusion). When saltwater reaches farmland, typical crops, like corn and soybean, which are not tolerant to salt, are unable to grow. As saltwater creeps further inland, it can cause a decrease in the productivity of nearby fields, eventually forcing some farmers to abandon fields altogether.
At each farm, I collected a soil sample in order to test the electrical conductivity of the soil. The soil’s electrical conductivity correlates to how salt level in the soil. With this measurement, we can understand the magnitude of which saltwater intrusion could be impacting crop productivity in each field that I visited, and infer how it is affecting other crop fields in the surrounding areas.
On the days I am not wearing my bucket hat, I am instead at UMD's McKeldin Library’s Geographic Information System (GIS) and Spatial Data Center sitting in my bucket seat (which my mom also got for me) working on visual display of the data I collected out in the field, as well as a remote sensing project that identifies areas of saltwater intrusion and other land cover changes from satellite imagery. This aspect of my work has been exciting for me because it puts the data into a visual and colorful map display that makes the long list of numbers easier to understand. I hope that the final product of my geospatial data work helps others understand how imminent and important issues like sea level rise and climate change are, and how they can impact our food systems and livelihoods at any moment!
- By Liz Nguyen
Shielded from the rest of the world by century-old townhomes lies a roughly quarter-acre plot in the heart of Columbia Heights, D.C. For years, the dirt beneath this plot was abused. Forgotten screws, used needles, and tiny glass pieces riddled the ground. Oil and grease that had once dripped from the underside of rusty old cars suffocates the soil below leaving it tainted with lead.
Roughly twenty years ago, new money began to pour into Columbia Heights. High-dollar developments replaced rundown townhomes, boutique shops and hip restaurants lined the streets. From the outside, Columbia Heights was flourishing. But for the longtime residents, who for generations called Columbia Heights home, a different reality was setting in. For most, the notion of prosperity in the old NW D.C. car park-turned courtyard seemed unimaginable. But, in 2010, Washington Parks and People had the opportunity to salvage the then abandoned lot and transform it into a place for the people. A place for life, personal expression, and community -- a place to thrive. In 2010, Columbia Heights Green was born.
Over the next nine years, and countless hours of volunteering that have followed, Columbia Height’ers have transformed the abandoned car lot into a thriving urban farm producing food from the people, for the people.
How We Operate
On most days, the Columbia Heights Green is quiet (aside from construction workers demolishing the surrounding old townhomes). Passersby often stop to peer over the Green’s fence and appreciate the little garden oasis that’s tucked away in this D.C. alleyway. Aside from the occasional watering, the green quietly chugs away, growing food as we go to work and school. But on Saturday mornings, the Green truly comes to life. Members of the community come together to tend to the plants, pick weeds, erect new structures, and transplant, harvest, and share the communally grown food.
Columbia Heights Green operates a little differently than your normal community garden. Instead of allocating specific plots per community member or household, everything at Columbia Heights Green is grown communally. Not only does this model of community farming allow the farm to be nearly six times more productive than the traditional plot-per-person model, but it also aligns the collective farming knowledge of all the residents together, allowing for better problem solving and management on the farm.
Since employing the collective community model style of growing, we’ve been able to produce a lot more food. In the heat of the growing season, we will usually grow more food than our community volunteer members alone can eat. In these instances, we donate our food to local food banks including Miriam's Kitchen, Martha's Table, and the Sacred Heart Church Dinner Program.
A few years ago, I was studying the effects of salinity on soil greenhouse gas production and denitrification rates in coastal wetlands of Louisiana. Meanwhile, I did not know there was a saltwater intrusion (SWI) problem facing coastal agricultural systems, especially in the Lower Eastern of Maryland (LES). Saltwater intrusion occurs when saltwater moves further inland, often leaving farmlands unproductive, and possibly displacing nutrients into downstream waters (Ardón et al. 2013; Ardón et al. 2017; Tully et al. 2019). Kate Tully’s lab, among others, are looking to tackle this environmental challenge head-on. I had the pleasure of working as a research technician on this project for 8 months.
During my first day of fieldwork in the summer of 2018, I met Kate Tully and Elizabeth de la Reguera at our rental van, packed up, and drove 3 hours to the LES of Maryland for a day of plant germination and survival counting. It was about 90°F with oppressive humidity and a constant threat of mosquito and tick bites. This does not compare to latter days in the summer, with heat indexes rising closer to 106°F. Here are a few other technician duties that I typically performed:
Research Technicians play an important role in large-scale, long-term, and interdisciplinary projects like this one. I am lucky to have been able to work with such an impressive team and be in charge of coordinating the biogeochemistry analyses for an important environmental challenge. I am definitely looking back on the Good Ol’ Days with rose-colored glasses!
Ardón M, Helton AM, Scheuerell MD, Bernhardt ES (2017). Fertilizer legacies meet saltwater incursion : challenges and constraints for coastal plain wetland restoration. Elementa: Science of the Anthropocene 5:41.
Ardón M, Morse JL, Colman BP, Bernhardt ES (2013). Drought-induced saltwater incursion leads to increased wetland nitrogen export. Global Change Biology 19:2976–2985.
Tully KL, Weissman D, Wyner WJ, Miller J (2019). Soils in transition : saltwater intrusion alters soil chemistry in agricultural fields. Biogeochemistry.
-By Natalie Ceresnak
When we appreciate the brilliant blue of the Chesapeake Bay, salted water silently invades lands that we live on due to global warming. This phenomenon is referred as saltwater intrusion (SWI), when saline water moves into fresh aquifers and surface water. New research is showing that SWI can disrupt nutrient cycling in coastal regions (Ardón et al 2013; Ardón et al 2017). In the Lower Eastern Shore of Maryland along the Chesapeake Bay, coastal farmland is subject to severe SWI and extensive agricultural areas will be lost in the coming decades (Shepard et al 2013). These coastal farmlands and adjacent areas (i.e. forests and marshes) provide important economic, social, and environmental functions in the region (Tully et al 2019).
Don’t worry, we researchers in AgroEcoLab, are here to investigate and solve this pressing problem! My work with Dani Weissman this semester is to further investigate the impact of saltwater intrusion on nutrients (i.e. nitrogen and phosphate) in active farm fields on the Lower Eastern Shore of Maryland. By reading all research papers provided by Dani, I learned that the saltwater includes rich ionic components (i.e. sulfate, sodium, etc.) that can bind to iron in soils stimulate the release of nutrients into soil porewater and surface water (Chambers and Odum 1990). It inspired me to develop an independent summer study on answering how the ionic components of saltwater affect nutrients in soils.
Thanks for this great opportunity offered by AgroEcoLab, I can experience working in a professional laboratory and apply my chemistry knowledge in practice. Until now, I have helped with sample preparation, experiment set-ups and data analysis. I still remembered the exciting moment when I obtained a perfect calibration for pipets (Figure 1); the cheerful moment when Dani and I finally resolved the instrumental issues (Figure 2). Participating in this saltwater intrusion projects not only provides me joys and self-fulfilling but also helps me develop professional research skills and enhances my understanding of environmental knowledge. My time in the AgroEcoLab is giving me an important foundation for me to attend graduate school in the future.
Ardón M, Helton AM, Scheuerell MD, Bernhardt ES (2017) Fertilizer legacies meet saltwater incursion : challenges and constraints for coastal plain wetland restoration. Elementa: Science of the Anthropocene 5:41. doi:10.1525/elementa.236
Ardón M, Morse JL, Colman BP, Bernhardt ES (2013) Drought-induced saltwater incursion leads to increased wetland nitrogen export. Global Change Biology 19:2976–2985. doi:10.1111/gcb.12287
Chambers RM, Odum WE (1990) Porewater oxidation, dissolved phosphate and the iron curtain- Iron-phosphorus relations in tidal freshwater marshes. Biogeochemistry 10:37–52. doi:10.1007/BF00000891
Shepard A, Curson D, Patton K, Dubois N (2013) Sea-level Rise Is for the Birds: Landscape-level Conservation Planning to Protect Communities, Coastal Wetlands and Salt Marsh Birds. 20.
Tully KL, Weissman D, Wyner WJ, Miller J (2019) Soils in transition : saltwater intrusion alters soil chemistry in agricultural fields. Biogeochemistry. doi:10.1007/s10533-019-00538-9
- By Tia Ouyang
On an uncharacteristically warm couple of days in early February, Kate, Elizabeth, and Dani attended the first annual Marsh Resilience Summit hosted by the Virginia Institute of Marine Science (VIMS) in Williamsburg, Virginia. This event was organized to bring together researchers, non-profit groups, wetland restoration practitioners, and other stakeholders to address issues related to coastal marsh restoration in the face of climate change. There was so much interest in the summit that VIMS had to move it off their campus to a nearby hotel to accommodate all the attendees. Over 200 people were present! A large portion of the event was dedicated to discussing the Chesapeake Bay Sentinel Site Cooperative. Sentinel sites are research stations where scientists measure changes in coastal ecosystems throughout the Bay. The summit was in part organized by Keryn Gedan, Assistant Professor of Biology at George Washington University and one of our very close project collaborators!
Kate gave a wonderful talk entitled Agroecosystems in transition: sea level rise and saltwater intrusion alter biogeochemical cycling in coastal farmlands and Dani and Elizabeth presented posters on their current research. Dani’s poster was on her three summers of work collecting water sample data from coastal farms, marshes, and forests. Elizabeth’s poster was on carbon fractions on farm fields undergoing saltwater intrusion. (Shout out—she won the Outstanding Student Presentation Award for her talk, based on this poster, at the annual American Geophysical Union conference). There she is below with her awesome poster and the newest little ecologist—Toby Gedan! Of course, Toby told us that he loved all of the wetland talks that Keryn took him to during the conference.
The summit included many discussion-stimulating talks related to marsh migration, opportunities to enhance conservation policies, coastal community resilience, wetland ecosystem services, management and restoration techniques, dredge materials, living shorelines, and relationships between marshes, agriculture and industry. Though this summit wont be held for another few years, it certainly sparked a great amount of sharing of ideas and collaboration between people interested in protecting the marshes, in the Chesapeake Bay and worldwide!
-By Dani Weissman and Elizabeth de la Reguera
Check out the new article in Civil Eats on saltwater intrusion and nutrient release from coastal farmlands.
Check out the latest publication by the AgroEcoLab! In this paper we look at the effects of sea-level rise and associated saltwater intrusion on soil chemistry in coastal farm lands. We show that saltwater intrusion dramatically alters soil chemistry, with consequences for carbon and phosphorus retention and loss.
Check it out here.
This semester I’ve had the pleasure of working with Elizabeth de la Reguera and Natalie Ceresnak on different projects under the saltwater intrusion (SWI) research umbrella. Saltwater intrusion is the movement of seawater onto land and into freshwater aquifers. This phenomenon is occurring in many coastal regions, including the Maryland Eastern Shore, and can have detrimental effects on agriculture. Thankfully, researchers like Elizabeth and Natalie (and by assisting them, me) are investigating this pressing problem!
My main work with the Agroecology lab revolved around Elizabeth’s carbon fractionation work, which investigates carbon storage across a spectrum of salt concentrations and soil depths. In soils, carbon binds to other soil constituents, such as minerals and salts, to create stable assemblages within large and small soil aggregates (von Lutzow et al., 2007). Where carbon is stored plays an important role in salt-damaged farm fields because understanding the effect of sea salts on the storage and stability of carbon can help determine if these transitioning tidal wetlands on the Eastern Shore would be more valuable (in terms of carbon sequestration) than growing crops. I’ve been able to assist Elizabeth with this research by entering sample data into a massive spreadsheet, and I’ve also helped organize her 1,500 soil sample envelopes based on a certain site name, soil depth, AND particle size.
My work with Natalie was also related to SWI and its impacts on soil biogeochemistry. Her research investigates how different cropping treatments affect nutrient accumulation and losses on saltwater intruded fields before, during, and after field trials. Seawater cations can compete with and replace nutrient ions (like ammonium) by binding to soil particles, and fields inundated with saltwater can thus lose these nutrients (Steinmuller & Chambers, 2018). Using samples from the same sites as Elizabeth’s, a colorimeter will soon be used to measure nitrate, ammonium, and phosphate to see if this is occurring on the Eastern Shore. Electrical conductivity (as a proxy for salinity) will also be measured to see where in the field and at what depth we find to be saltiest.
When I started working in the Agroecology lab, I had only a general idea about saltwater intrusion, but I now have a better understanding of how serious a problem it is for agriculture. From working with both of these projects, I’ve learned that SWI can affect all aspects of soil chemistry and crop health in ag fields right here on our coasts. My work in the lab has helped hone my organizational skills and has taught me that soils research requires careful and precise work. It’s been a great opportunity to work in the Agroecology lab and to be a part of such important ag research!
- By Taylor Brinks
Steinmuller, H., & Chambers, L. (2018). Can Saltwater Intrusion Accelerate Nutrient Export from Freshwater Wetland Soils? An Experimental Approach. Soil Science Society of America Journal,82(1).
von Lützow, M., Kögel-Knabner, I., Ekschmitt, K., Flessa, H., Guggenberger, G., Matzner, E., & Marschner, B. (2007). SOM fractionation methods: relevance to functional pools and to stabilization mechanisms. Soil Biology and Biochemistry, 39(9), 2183-2207.