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!