I am a colossal soil nerd; I try to learn as much about soil as possible. However, most of my knowledge comes from a classroom setting, which, frankly, is not the most effective way to learn about soils. Soils are best observed with our senses: sight, touch, and smell. Thanks to my internship at the Agroecology Lab at the University of Maryland, I have been able to apply my classroom knowledge—and passion—to real-world problems. One of these problems involves understanding the consequences of saltwater intrusion on coastal farmlands.
Upon starting my internship, I was completely unaware of saltwater intrusion. I broadly understood that climate change affected food systems through rising sea levels, droughts, and storms. I had not considered how these consequences cause salt from the ocean to seep into agricultural soils, damaging crops. Average yields for critical crops can decrease as much as 50% as a result of sea level rise, droughts, and storms (Shrivastava and Kumar 2015). Rising sea levels brings salt directly into freshwater systems, heavy coastal storms can carry salt from the ocean inland, and droughts can cause salt to accumulate in the soil.
It is crucial to note that climate change is not the only way salt from coastal systems is intruding inland. Extracting freshwater from the ground and existing water control infrastructures, such as canals and ditches, can carry saltwater to inland soils (Tully et al. 2019). Studying agricultural ditches and canals will improve our ability to adapt coastal agricultural lands to rising sea levels and storm surges associated with climate change.
As I've become more familiar with the issues affecting our soils on the Eastern Shore, I have also learned some critical laboratory skills that I did not know before. I had the opportunity to join the lab in the field to collect soil samples, and I process soil samples in the lab with my mentor, Silver. I believe that I am growing as a scientist from working in the Agroecology lab, and I deeply enjoy working with the Agroecology Team. They understand the value of soil, and they know that our lives depend on understanding and protecting it from assault.
Shrivastava, P., & Kumar, R. (2015). Soil salinity: A serious environmental issue and plant growth promoting bacteria as one of the tools for its alleviation. Saudi journal of biological sciences, 22(2), 123–131. https://doi.org/10.1016/j.sjbs.2014.12.001.
Tully, K., Gedan, K., Epanchin-Niell, R., Strong, A., Bernhardt, E. S., BenDor, T., ... & Weston, N. B. (2019). The invisible flood: The chemistry, ecology, and social implications of coastal saltwater intrusion. BioScience, 69(5), 368-378.
- By Mary Gumerov
Saltwater intrusion can be devastating, not just to farmers but to the environment, native species, and ultimately the economy. There are both natural and unnatural factors that drive saltwater intrusion. The five main factors include sea-level, storms and tides, drought, water usage, and hydrologic connectivity . The devastating effects of salinization of farmland due to these factors may include coastal forest loss, salt-tolerant species invasion, decline in crop yields, eutrophication, and marsh migration . While one may think that heavy rainfall and sea-level rise would cause the most rapid salinization of agricultural systems, it is actually drought. Although Maryland’s recorded rainfall this year, 2020, is relatively normal, December 2016 – January 2018 experienced significantly decreased rainfall and even emergency drought conditions in central parts of the state . During a drought, rivers, streams, and other bodies of water become more concentrated with salt, thus allowing nutrient leaching [of fields] to occur at a greater rate. Additionally, the highly concentrated salt affects the ion exchange rate, for example, dehydrated sodium is a powerful positively charged ion, or cation, affected by this change . Legacy nutrients are nutrients that have built up in the soil over time. Soil, particularly clay soil, can hold onto these nutrients via ionic bonds. While these nutrients are not immediately bio-available to crops currently growing, if leached and subsequently washed away these nutrients contribute largely to algae blooms and eutrophication in bodies of water. Yet, with a more attractive, stronger ion (salt), now in the soil, the soil particles may bind to the salt, effectively unbinding from the legacy nutrients (usually nitrogen [N] and phosphorous, [P]). While unbound, the legacy nutrients can be more easily washed away and removed entirely from the field.
There are many methods for evaluation of the level of saltwater intrusion into a farm system. The Tully Laboratory often measures concentrations of different nutrients using extractions. One nutrient often measured is phosphorous. I have been assisting in making the solutions necessary for sequential P extraction in soils, including sodium bicarbonate, sodium hydroxide, and hydrochloric acid. Each sequential extraction (using a different solution) extracts a different form of phosphate found in the soils. Lastly, the P samples are analyzed using the LACHAT (a type of spectrometer) for colorimetric analysis. However, some samples are too acidic, creating bubbles in the tubing of the LACHAT, resulting in a poor curve. This can also be true for a very basic solution. Early in the semester, I assisted in adjusting a very basic (pH 13) extraction to a lower basicity (pH 8) to fix this dilemma.
 Tully, K., Gedan, K., Epanchin-Niell, R., Strong, A., & Bernhardt, E. S. (May, 2019). The Invisible Flood: The Chemistry, Ecology, and Social Implications of Coastal Saltwater Intrusion. Bioscience, 69(5), 368-378. doi:10.1093/biosci/biz027
 Maryland Department of the Environment. (2020, September). Maryland's Drought Status: Current Conditions. Retrieved from https://mde.maryland.gov/programs/water/droughtinformation/currentconditions/Pages/index.aspx
 Tully, K. L., & Weissman, D. S. (February, 2020). Saltwater intrusion affects nutrient concentrations in soil porewater and surface waters of coastal habitats. The Ecological Society of America, 11(2). doi:10.1002/ecs2.3041
- By Madison Curtis
On Thursday, 29 October 2020, Resham Thapa successfully defended his PhD on decomposition and nitrogen release from cover crops. He produced an amazing body of work while in the Agroecology lab, including two publications not related to his dissertation! We are thrilled that Dr. Thapa is staying on to do a postdoc with us and remain a part of the Precision Sustainable Ag team! CONGRATS, DR. THAPA!