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
At 5:00 am on a Wednesday morning the sun has yet to rise in the Pocomoke River State Forest, but our team is already up cooking breakfast and putting on our boots to prepare for a day of work in the field. It’s important for us to get an early start in an attempt to beat some of the Maryland summer heat, or to make up for lost hours due to yesterday’s afternoon thunderstorm. We load up our truck with tape measures, augers, fertilizer, and of course our plants, switchgrass (Panicum virgatum) and saltmeadow corgdrass (Spartina patens). The purpose of this field excursion is to plant several salt tolerant crop species in order to see how they fare in the increasingly inundated and brackish farm fields of the eastern shore of Maryland, one of the regions most vulnerable to the effects of sea level rise in the entire country.
This summer I have been lucky enough to join the AgroEco Lab’s saltwater intrusion team and come along on multiple field excursions, where I have gotten to experience field work first hand and get a sense of what a typical day in the field looks like. Some may assume that scientists are only there to observe, and simply stand by making tick marks on their clipboards while others do the dirty work...but this couldn’t be further from the truth! One important thing I have learned this summer is that agroecologists are not afraid to get their hands dirty, and field work involves a great deal of manual labor, such a making soil “slushies” in order to install lysimeters, hammering probes 60 cm into the ground to get soil samples, and crawling up and down plots to plant our treatments.
During this planting excursion in particular I was thrown into the reality of field work: that it’s really hard! It involves long hours (sometimes dawn to dusk!), exposure to all kinds of weather, including sweltering heat and torrential downpours, strenuous labor, and worst of all, ticks! While some may know the eastern shore of Maryland for its picturesque landscapes of tall grasses blowing in the breeze against the backdrop of the Chesapeake Bay, or perhaps its delicious crab dinners, our field trips are certainly no vacation!
But sometimes these field excursions don’t seem like work at all, and the lines between work and leisure are more blurred. For instance, when I’m standing out on a wooden dock overlooking the bay, and behind me is a small cottage and willow tree that belong to a historic property, just down a dirt road from one of our field sites. Or when I get back from a long day in the field only to enjoy a lively make-your-own taco night with the rest of team, an evening fueled with laughter, stories, and an appreciation for good food. For all the things that make field work hard, there are plenty more that make it an incredible experience overall. As agroecologists we are lucky enough to get to go to so many extraordinary places and spend time outdoors, as well as get to bond with our fellow researchers, as a part of our job, which is a luxury not everyone has. I cannot wait to see all the places agroecology research will take me in the future!
- By Louisa Kimmell
Anderson, Eric K., et al. “Determining Effects of Sodicity and Salinity on Switchgrass and Prairie Cordgrass Germination and Plant Growth.” Industrial Crops and Products, vol. 64, Feb. 2015, pp. 79–87., doi:10.1016/j.indcrop.2014.11.016.
Titus, JG, and C Richman. “Maps of Lands Vulnerable to Sea Level Rise: Modeled Elevations along the US Atlantic and Gulf Coasts.” Climate Research, vol. 18, 2 Nov. 2001, pp. 205–228., doi:10.3354/cr018205.
If you have been around me in the lab for the last month, you might have caught me a few times watching a soccer game while scraping away soil samples. When there is a huge bin full of samples to scrape, you need something to pass the time. As a huge soccer fan, the World Cup brings me excitement every four years when it rolls around. Some of the countries I closely followed in this World Cup have players with great individual skill but have mostly gotten their nation to advance solely on team chemistry. So far, this observation has paralleled my experience in the Agroecology lab this summer.
I am working individually most days on Elizabeth de la Reguera’s project about how saltwater intrusion affects the storage of carbon in soil on agricultural fields. In this project, different soil aggregates are separated by sieving them from large to small particle size, until eventually silt and clay is left in the end. After the aggregates are dried in an oven, I weigh them and take them back to scrape in coin envelopes (shown in the picture). The amount of carbon is then tested after the samples are in envelopes. This work is important in observing how outside forces like saltwater intrusion can greatly affect aggregate stability . This research will hopefully help farmers take saltwater intrusion into account and seek solutions, such as establishing barriers to mitigate intrusion rate or adjusting crops to salt-tolerant species .
With the many individual projects the lab has, our “team chemistry” is still displayed. On a small scale, Elizabeth and I communicate well to ensure that her project is running smoothly. This can include relaying turkey tins to her car from the drying oven, needing more samples in the lab, or teaching me something new. In the field a couple weeks ago, I was part of a team of six when it came to installing lysimeters and soil sampling. We knocked out two fields in one day and got to go home a day early! On a large scale, the goal of our lab is to make agriculture more sustainable through research. We all know we aren’t making as much money as Messi or Ronaldo, but together we are definitely making an impact in the environmental and agricultural world. Even with the World Cup coming to an end soon, I still have a lot of great experiences left in the lab this summer.
-By Drew Mandich
USDA Natural Resources Conservation Service. (1996). Soil Quality Indicators: Aggregate
Stability. Retrieved from
Duan, Y. (2016). Saltwater intrusion and agriculture: a comparative study between the
Netherlands and China. TRITA-LWR Degree Project 2016:20.
We are interested in varying osmotic potentials because we want to know if crop death seen on saltwater intruded farm fields is due to the inability of plants to pull water out of the soil matrix or because of salt toxicity. This work will be complemented by another experiment of seed germination at varying sodium chloride (NaCl) concentrations in order to tease apart whether seeds are experiencing osmotic stress or ionic/salt stress.
This first year has been a year of logistics! Between field work on the lower eastern shore, to aggregate fractionation at the University of Maryland College Park, to seed germination experiments and George Washington University, I feel like the ring leader of a scientific circus. The second year can only be crazier and more exciting with all the data to analyze and a story to tell!
- By Elizabeth de la Reguera
Six, J., K. Paustian, E.T. Elliott, C. Combrink. 2000. Soil Structure and Organic Matter: I. Distribution of Aggregate-Size Classes and Aggregate-Associated Carbon. Soil Science Society of America Journal. 64:681-689.
Weil, R.R. and N.C. Brady. 2016. The Nature and Properties of Soils. 15th ed. Pearson Education, Columbus. ISBN: 9780133254488
This week, the Agroecology lab was all over the news!
A piece about our research on sea-level rise and saltwater intrusion aired on NPR's Weekend Edition. Check out the piece here.
Kate also presented at the Wilson Center on Sustainable water and resilient communities. Check out the webcast and news coverage at NewSecurityBeat.
Today marks the end of my time as an intern in the Agroecology Lab. I have been fortunate enough to spend the entirety of my senior year working in the lab with Dani Weissman and the other graduate students, Cullen McAskill the wonderful lab technician, and my fellow interns. Through my various research experiences in the lab, I have learned so much about biogeochemical cycling processes that impact agriculture, the importance of agroecology to integrate ecological and social approaches to agriculture, and standard chemical analysis research practices.
This semester I focused my efforts on a long-term research study to understand different nutrients, like nitrogen and phosphorus, that are dissolved and bound to soil particles in water samples taken from various agricultural plots on the Eastern Shore. Nitrogen in this form is formally called “Dissolved Organic Nitrogen” (DON), while other forms of nitrogen often found in the soil include nitrate and nitrite, which are necessary for plant growth. The agroecology lab is investigating these different forms of nutrients because it is important to understand how changing environmental conditions may impact the future of agriculture. Rising sea levels, for example, is causing saltwater from the ocean to intrude into agricultural plots on the Eastern Shore. This alters the chemical and biological processes that take place in agricultural soils (Osburn, 2016; Weston, 2006). To understand how nutrient forms have been changing over time in response to saltwater intrusion, I conducted digestion experiments on water samples to specifically target dissolved organic nutrients. Essentially, the experiment required me to add various chemicals to the water samples (as shown in Figure 1) and then run them through an autoclave, which heats the samples up to extremely high temperatures. This breaks up any bonds between the nutrients and dissolved soil components to isolate the nutrients to be further analyzed.
The results of this experimental digestion process will provide important information on plant nutrient availability once they undergo a next step of further chemical analysis. It is a good feeling to be able to contribute to the research findings of the Agroecology Lab. I will sorely miss my time working there now that the semester has come to a close, but I will be forever grateful to all that I have learned and for how it has changed my perspectives of agroecology.
Osburn, Christopher L., Lauren T. Handsel, Benjamin L. Peierls, and Hans W. Paerl. 2016. “Predicting Sources of Dissolved Organic Nitrogen to an Estuary from an Agro-Urban Coastal Watershed.” Environmental Science & Technology, 50: 8473-8484.
Weston, Nathanial B., Ray E. Dixon, and Samantha B. Joyce. 2006. “Ramifications of increased salinity in tidal freshwater sediments: geochemistry and microbial pathways of organic matter mineralization. Journal of Geophysical Research, 111: G01009.
- By Alexis Boytim
I am Jonathan Moy, an undergraduate intern in the Agroecology lab. I work with Elizabeth de la Reguera, an MS student here, in two of her projects. Her work is largely on how saltwater intrusion in Maryland affects the carbon found in soil. We recently finished transferring four thousand switchgrass plants to UMD’s greenhouse. Later in the year, the lab will be planting the switchgrass along with other salt-tolerant plants in saltwater intruded agricultural plots to determine the carbon the plants imparted in the soil. The data from that experiment will be helpful in giving farmers in Maryland a well-supported reason to use salt-tolerant crops in their crop rotations. The project I am working on right now examines the aggregate distribution in saltwater intruded agricultural fields. Soil aggregates are important to the available nutrients to the soils . We are most closely looking at soil carbon—thus the title of this post. Carbonation the way most people use it usually refers to carbon dioxide reacting with a beverage to make it effervescent. While that doesn’t happen in our soils, carbon is still very interesting in soils! The method we are using uses a series of sieves to separate the soil carbon by availability [2,3]. Essentially, the smaller the aggregates are, the less available the carbon is to the plants’ roots . One of the pictures with this post shows Elizabeth displaying the second smallest sieve we use in this experiment. Fun fact: the picture also features the very first sample we processed for this experiment.
During spring break, I was given the opportunity to visit the sites that we are working on! You may not be able to tell from the picture (I’m the guy in blue), but I had a blast soil sampling. If you look really closely, you can see that I’m smiling. Those soils were the same soils that we are processing right now, so that is just one more thing to be excited about when processing my samples. Before that, I spent a lot of time in the Greenhouse seeding, thinning, and transferring switchgrass until we had four thousand switchgrass plants individually growing in deep planting plugs.
- By Jonathan Moy
Ontl, T.A. et al. (2013). Topographic and Soil Influences on Root Productivity of Three Bioenergy Cropping Systems. The New Phytologist, 199, 727-737. doi: 10.1111/nph.12302
Elliott, E.T. (1986). Aggregate Structure and Carbon, Nitrogen, and Phosphorus in Native and Cultivated Soils. Soil Science Society of America Journal. 50, 627-633.
Six, J. et al. (2000). Soil Structure and Organic Matter: I. Distribution of Aggregate-Size Classes and Aggregate-Associated Carbon. Soil Science Society of America. 64, 681-689.
It is 9AM on a cold Tuesday morning in west Tennessee, and I find myself in a two-meter-deep pit in the middle of a farm field. The water in the ponded pit reaches up past the knee of my waders, and I can feel that my feet are stuck in the mud underneath. I can’t feel my fingers, but still I persevere, focusing on the task at-hand of acquiring samples from each horizon of the soil profile in front of me before I must get back out. This is just the start of a regular practice day during the week of the National Collegiate Soils Contest.
Five minutes in the pit, five minutes out. Ten minutes in, ten minutes out. Five minutes in, five minutes out. All followed by a twenty-minute free-for-all. Much like any other contest, soil judging has clearly defined rules. At the start of the contest, competitors are given scorecards and taken to soil pits. Each individual competitor has an hour at each pit to fill out their scorecard describing the morphology of the soil in the pit: its horizonation, structure, color, texture, redox concentrations, and taxonomy, just to name a few of the described features. After each competitor has judged every pit, the scorecards are graded for accuracy based on data collected by the hosting university. The individuals are ranked based on the highest combined scores.
The soils of Tennessee offered us great challenge and created much confusion with the presence of many unfamiliar features, such as the elusive glossic horizon, the cryptic lamellae, and the enigmatic plinthite; however, none of these features baffled us quite like the mysterious fragipan. Fragipans make up the dense, brittle subsurface layers hypothesized to form under conditions of compaction, deformation, and contraction (Graveel, Tyler, Jones, & McFee, 2002). As root- and water-limiting layers, calling a horizon a fragipan makes all the difference in correctly determining such important features as effective soil depth, depth to seasonally high water table, and water retention as well as soil taxonomy. Essentially, scoring well in the contest depended on correctly identifying fragipans. This may be appropriate, for the presence of and depth to a fragipan has major land use implications. Fragipans are shown to limit crop growth, with a study of soybean crops demonstrating decreases in both root growth and crop yields as depth to a fragipan decreases (Graveel, Tyler, Jones, & McFee, 2002). This issue becomes even more pressing in areas of loess deposition. The wind-blown silt blanketing the surface in such regions is highly vulnerable to erosion, especially in agricultural fields without proper erosion protection protocols, so these fields are at risk of losing yields over time due to this effective decrease in depth to fragipans.
The contest concluded with an awards ceremony under the iconic Eiffel Tower of Paris, TN. We took home fourth place overall, coming home with a lovely plaque and a much greater understanding of the soils of Tennessee.
- By Jonathan Wiechecki
Graveel, J. G., Tyler, D. D., Jones, J. R., & McFee, W. W. (2002). Crop yield and rooting as affected by fragipan depth in loess soils in the southeast USA. Soil and Tillage Research.
Smalley, I. J., Bentley, S. P., & Markovic, S. B. (2016). Loess and fragipans: Development of polygonal-crack-network structures in fragipan horizons in loess ground. Quaternary International.
I’ve been working with Cullen this semester, and since Cullen works on pretty much everything in the lab, I’ve had the privilege of being exposed to many different lab activities. I’ve gotten to work with Dynacrush the soil grinder, help weigh and prepare soil samples for KCl extractions, and use SamplePoint software to look at land cover and plant species diversity in field sites on the Eastern Shore. SamplePoint is a manual image analysis program that is used to classify different land cover types on individual nadir images . For each photo taken of the test plots, I classified one hundred different sample pixels as bare soil, plant litter, or one of about fifteen different plant species. SamplePoint then uses the manually-entered sample data to extrapolate the land cover classifications to the rest of the image. Quantifiable land cover data, such as the percent area of a plot that is covered by one specific plant species, can be a useful metric when assessing the impact of saltwater intrusion on plant species diversity.
One of the most rewarding experiences I’ve had so far in the lab has been the hands-on soil sampling work that we did over spring break at “soils camp.” We sampled several field sites that were experiencing saltwater intrusion, and it was fascinating to personally witness the visible signs of saltwater intrusion’s effects on these agricultural fields. There are generally very clear boundaries between the brackish water ditch inhabited by phragmites reeds, the adjacent area inhabited by low-lying salt-tolerant species such as salt marsh hay, the zone of generally bare soil, and then the transition into the agricultural field. By analyzing soil samples from these test sites, we can assess the impact that saltwater incursion has on nutrient release, carbon dynamics, nitrogen content, aggregate structure, and other soil properties  . Soils camp was a wonderful way to spend time outdoors, get covered in mud, work together with inspiring and fun people from the lab, and understand where and how the Agroecology Lab obtains the soil samples that we process and analyze back in College Park.
- By Anna Collishaw
Hello! I work with Josh Gaimaro in Dr. Tully’s AgroEcoLab. Josh’s research focuses on the cover crop management for nutrient cycling. Cover crops are planted between rotations of cash crops. They provides various ecosystem services and improve soil quality. On the first day of my work in the lab, Josh provided me with a brief introduction to his research, in which I learned more about cover crops. It is widely accepted that the cover crops can improve the soil by retaining and later releasing nutrients. They also reduce soil compaction and prevent nitrogen leaching losses. However, different species of cover crops may differ in their function and efficacy, which requires further study . Josh’s research looks into this problem and investigates the services provided by different species and mixtures of cover crops, including rye and radish. One important function of a cover crop is to remove excess nitrogen from the last cash crop and release it to subsequent crops in the spring . Rye and radish have different physical traits, and will differ in their performance of this action. We believe, that their combination might work even better. This is important information for both US agriculture and the global food system because nitrogen loss is a severe problem. Cover crops can help ameliorate this problem by increasing the efficiency of soil nutrient usage and reducing the application of synthetic fertilizer. Thus, Josh is exploring the effectiveness of different combinations of cover crops on nitrogen cycling, and I am helping him with the nitrogen uptake measurements.
My primary work in the lab are grinding soil samples and preparing the crop samples for analysis. To determine the nitrogen uptake, we need to know the amount of nitrogen in the soil as well as in the crops. Last year, Josh collected soil samples several times during the growing season. I weigh the soil after it has been air-dried and I grind the soil into even particles. For both soils and plant materials, I wrap a small amount into a piece of foil, so that we can analyze carbon and nitrogen content. The fun thing about two projects is that the crops come from “ashes” is turned into ashes in the lab; the dust from soil is also crushed into dust. So, I call my research project, “Ashes to ashes dust to dust”.