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.
This fall I started working in the Agroecology lab, helping with Elizabeth de la Reguera’s study investigating the effects of saltwater intrusion on agricultural land. Hundreds of soil samples were acquired, before my time, from sites located on the Lower Eastern Shore of Maryland to test for carbon storage potential. These field samples were separated into aggregate size classes by sequentially wet sieving, a process called carbon fractionation (Six et al., 2000). The samples were then ready to be oven dried for several days.
After oven drying the aggregate sizes, I began to work with the samples. My first weeks in the lab revolved around scraping the dried soil from their tins into coin envelopes to be used later. If you saw me in the lab around this point in time you would’ve saw a seemingly never-ending mountain of tins that I’d be chipping away at, needless to say I never had to worry about having nothing to do. In addition to scraping the tins, I eventually began to prepare and measure a small amount of soil from these coin envelopes to be used for carbon and nitrogen analysis.
In a broader context, I learned from this study that not only is the amount of carbon in soil important for agricultural purposes, but where that carbon is located is just as important. I found that carbon inside of macroaggregates, which is broken down easier, tends to be more labile and can be used by crops more readily than carbon located in microaggregates (John et al., 2005).
Most days I would work individually in the lab, but that does not mean that there is no team chemistry on this project. Elizabeth communicates with me on a regular basis to ensure that I understand what is currently going on. Additionally, Dr. Tully and others in the Agroecology lab encourage me to come forward if I have any questions. This individualistic yet team-rooted environment is one of my favorite things about working in the lab and makes me excited to continue learning new things and helping on this project!
- By Zach Johnson
John, B., Yamashita, T., Ludwig, B., & Flessa, H. (2005). Storage of organic carbon in aggregate and density fractions of silty soils under different types of land use. Geoderma, 128(1-2), 63-79.
Six, J., Paustian, K., Elliott, E. T., & Combrink, C. (2000). Soil structure and organic matter I. Distribution of aggregate-size classes and aggregate-associated carbon. Soil Science Society of America Journal, 64(2), 681-689.
Saltwater – it belongs in the ocean, right? Well, sort of. Saltwater can move inland through flooding during high tides or through the shallow groundwater table. This phenomenon is known as saltwater intrusion, is increasing in frequency as sea levels rise. This can cause big issues in areas like Maryland’s Eastern Shore communities, where farms line the coasts. These farms grow crops which can only handle so much salt, but as more saltwater silently creeps into these fields, these crop’s tolerances are exceeded, killing them. This salt-death can be caused by the drying out of plant roots (Ardón et al, 2017). In the Agroecology lab we want to tackle the issues saltwater intrusion causes on these coastal farms. Cover crops are crops planted during the off-season that cycle nutrients found in the soil, preventing them from leaching away through rainwater. Cover crops can be used to lessen the amount of nutrients that escape these agricultural systems, combating the impacts saltwater intrusion may have on coastal farms (Gómez et al, 2009). Through the proper planting of select cover crops, farms in places like the Eastern Shore may stay in business longer, but it’s going to take some research to figure out the secret formula.
Observing cover crop impact requires lab work. For me, this means working in two places, the greenhouse and the Plant Sciences building. While at the greenhouse, I sort and filter porewater samples. Porewater is water that is found between the small spaces between soil particles, which have been collected from farm soils on the Lower Eastern Shore of Maryland that may be influenced by saltwater intrusion. At the Plant Sciences building, Dani Weissman and Natalie Ceresnak run filtered samples on a colorimeter to detect nitrogen and phosphorus levels, while another sample is used to measure pH, salinity, and conductivity. Soil chemistry plays a direct role in the development of planted crops, and by studying the chemical content of these samples we can find how to properly mitigate the impacts of saltwater intrusion.
Ardón, M., Helton, A. M., Scheuerell, M. D., & Bernhardt, E. S. (2017). Fertilizer legacies meet saltwater incursion: Challenges and constraints for coastal plain wetland restoration. Elementa, 5(0), 41. doi:10.1525/elementa.236
Gómez, J. A., Guzmán, M., Giráldez, J. V., & Fereres, E. (2009). The influence of cover crops and tillage on water and sediment yield, and on nutrient, and organic matter losses in an olive orchard on a sandy loam soil. Soil and Tillage Research,106(1), 137-144. doi:10.1016/j.still.2009.04.008
- By Ethan Glaudemans
If you have been in the lab over the past month when I’ve been working with Dani Weissman’s water samples from various agricultural plots along the Eastern Shore, you most likely walked into the awful smell of rotten eggs. This smell comes from bacteria that thrive in low oxygen environments and feed on small amounts of sulfur that is present within the water in places such as agricultural ditches. Although these samples are not necessarily pleasant to work with, they are important when considering the long-term project that Dani has been working on since 2016. We are analyzing these samples to examine the levels of nitrogen (N) and phosphorus (P) loading in the Chesapeake Bay estuary in response to saltwater intrusion. These studies of coastal agricultural communities are extremely important as they are the leading edge of climate change. The intrusion of saltwater from rising sea levels and coastal flooding can cause an unpredictable source of nutrients (N & P) to waterways along the Eastern Shore. Past applications of N and P on farms are remobilized by the intruding waters, which is the main source of the nutrients. The lab work that I am helping Dani with this semester, coupled with the past two years of data, will be used to help illustrate the effect of saltwater intrusion on our coastlines.
My experience in the lab so far this semester has been very informative and interesting. I have learned many things up to this point and anticipate learning many more. At the beginning of the semester, I measured out samples for dissolved organic phosphate, which Dani then ran on the flow-injection colorimeter. I’ve also learned how to run a standard curve and have had a chance to help run the atomic absorption spectrometer. As of late, I have been analyzing water samples for electrical conductivity and pH and preparing more samples for P measurements. This has all been valuable information that I will use in the future. As it is still rather early in the semester, there is plenty of time and opportunity to learn new things and to continue helping Dani with her project!
- By Kenny Polk
Ardón, M., A. M. Helton, M. D. Scheuerell, and E. S. Bernhardt. 2017. Fertilizer legacies meet saltwater incursion: challenges and constraints for coastal plain wetland restoration. Elementa Science of the Anthropocene 5: 41.
Hartzell, J. L., and T. E. Jordan. 2010. Shifts in the relative availability of phosphorus and nitrogen along estuarine salinity gradients. Biogeochemistry 107:489–500.
The AgroEcoLab is seeking a PhD student to work on our saltwater intrusion project! See all details and how to apply here.
Recent research in the agroecology lab shows that cover crop reduce nitrate leaching by as much as 56% compared to farms without cover crops. Check out the new article here!
My intern experiences this summer were nothing short of great. This summer, I helped Anna Kottkamp with her study of Delmarva Peninsula’s geographically isolated wetlands or Delmarva Bays. These wetlands are surrounded by upland and have no apparent surface water connectivity (Tiner 2003). Despite their geographic isolation, Delmarva Bays offer many ecosystem services such as providing habitat to many rare and endangered species (Sharitz and Gibbons 1982) and enhance local water quality (Phillips et al 1993).
With the lab and field work required to study these wetlands, I learned valuable skills that I can apply in my future career. One of these lessons is field preparedness. Whether your work is in the woods or in agricultural fields, or whether you are soil sampling or water sampling, fieldwork is an essential part of research and it comes with physical and environmental hazards. This guide is intended to share some things that I did right and some lessons I learned the hard way when it comes to field preparedness.
Phillips PJ, Denver JM, Shedlock RJ, Hamilton PA (1993) Effect of forested wetlands on nitrate concentrations in ground water and surface water on the Delmarva Peninsula. Wetlands Wetlands 13: 75-83.
Sharitz RR, Gibbons JW (1982) The ecology of southeastern shrub bogs (pocosins) and Carolina Bays: a community profile. FWS/OBS-82/04. US Fish and Wildlife Service, Division of Biological Services, Washington, DC
Tiner, R. (2003). Estimated extent of geographically isolated wetlands in selected areas of the united states. Wetlands, 23(3), 636-652.
-By Bianca Noveno
Salt-water intrusion (SWI) is a new challenge for farmers on the Eastern Shore. As sea levels continue to rise, more and more farm fields are becoming increasingly “salty,” often resulting in reduced and even complete loss of productivity. To make matters worse, there is evidence that salt accumulation also increases phosphorus loads to downstream waters. In the case of the Chesapeake Bay, this could reverse recent restoration efforts and hard fought water quality improvements.
Kate Tully, Keryn Gedan, and others are studying this problem; and their work aims to provide solutions that both help farmers and mitigate potential water quality degradation. Read more about their work in recent articles in NPR and The Atlantic.
This week, I helped Kate and Keryn install new groundwater wells at several of their sites. I had a great time and definitely learned a lot about agriculture on the Eastern Shore and salt-water intrusion. Below are a few pictures!
- By Nate Jones (postdoc at SESYNC)
At the AgroEcology lab, I primarily work with Josh Gaimaro on his research pertaining to cover crop use as a best management practice. Within my first two weeks of working in the lab, I was introduced to potassium chloride (KCl) extractions, which are one of the central procedures to his project. KCl extractions allow us to quantify the nitrogen concentration in soils, which helps model how the nitrogen moves through the soil, and how much of it gets taken up by plants or leached. Over the past two years, Josh collected over 1,000 samples, all which needed to be organized, weighed out, and extracted. Additionally, each sample required a replicate for quality control, which doubled the extraction count. When I was first introduced to the procedure, I did not understand the sheer quantity of samples I would need to process...
The first KCl extraction wasn’t perfect, even though Josh made the entire process look quick and effortless at first glance. The procedure is as follows: After weighing out a set of soil samples, we calibrated a pipette to dispense KCl into each tube. Afterwards, these samples are transferred to a shaker table, where they shake for an hour. In the meantime, you must prepare for the extraction which consists of setting up scintillation vials, placing funnels into them, and folding filter paper for each sample. Next, the tubes must go on a centrifuge to speed up filtering. However, we could only centrifuge 12 samples at a time, so it would take some time to get through all the samples. After the centrifuge, the samples are all filtered and organized once again.
The first extraction was around 75 samples, which wasn’t too intense since I was shadowing Josh and he was leading the procedure. Everything ran smoothly until the very end, where we were pouring the samples into the vials. We were using a shaky wooden device, which held the funnels a little above the vials, but didn’t secure the vials from moving. As I was pouring a sample, I accidentally knocked one over and it caused a domino effect! Three samples went down, and I was utterly embarrassed. Josh assured me that it is no big deal, and that we will redo these samples another day. Little did I know, I would do an extraction just like this at least twice a week at the minimum throughout the entire summer. The following day I was asked if I could do an extraction by myself with the help of another intern. Without giving it much thought, I replied “sure”, and began my journey of KCl extractions.
Once I got into the groove of things and familiarized myself with the procedure, I was averaging at 300 KCl extractions per day. This included the entire process- starting with weighing all the samples to cleaning up all of the dirty funnels and tubes. Little by little, I started working through these samples until the number of extractions left to do was zero. At first, the process didn’t seem to have an end, but somehow after three months of work, we finally finished the samples. Our last extraction was last Thursday, and was definitely bittersweet.
- By Christina Bychkov
Jones, D.L, Willett, VB. (2006) Experimental evaluation of methods to quantify dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) in soil. Soil Biology and Biochemistry, 38:5: 991-999 https://doi.org/10.1016/j.soilbio.2005.08.012.
Murphy, D., Macdonald, A., Stockdale, E. et al. (2000) Biol Fertil Soils 30: 374. https://doi.org/10.1007/s003740050018