Studying mixtures of different types of plants as a cover crop is an emerging trend.

“A lot of farmers plant a single type of cover crop,” said Miller. “But, now there is a big push toward mixing. A biomass builder, such as a tall cereal rye, pulls nitrogen out of the soil in the fall, and clovers add nitrogen in the spring when the cash crop needs the nutrient. We get both out of a cover crop mixture.” 

“While use of cover crops has become more popular in Delaware in the past few years, growers still have questions about how to best manage cover crops to achieve the desired environmental benefits and realize profitable cash crop yields,” added Shober.

Traditional cover crops used in crop rotation are typically classified into cereal grains, such as sorghum, triticale, cereal rye, annual ryegrass; brassicas, such as canola or rapeseed, radishes and legumes such as crimson clover or hairy vetch. Cereal rye, hairy vetch and crimson clover grow quite tall and add biomass and organic matter for soil health.

“We are trying to hit a sweet spot when managing cover crops,” Shober said of the study. “We want to produce enough biomass to provide benefits like nitrogen scavenging, weed suppression or nitrogen fixation (in the case of the legumes). But, we also want to make sure that cover crop residues will not negatively impact planting, emergence or early season nitrogen uptake by the agronomic crop.”

With 2020 marking the second year of the study, Taraila and her faculty mentors frequently visit both locations where three different cover crop conditions are observed. Two mixes are planted — cereal rye with crown vetch and cereal rye with clover, and another planting of rye alone. Observations are also made on control plots without any cover crop.

On her visits to research plots, Taraila collects a tissue section of the cover crop and sends specimens to UD’s soil lab to determine the carbon and nitrogen (N) ratio.

“That gives us density and weight,” Taraila said. “We also take soil samples at two depths in each plot, then the soil testing lab will analyze for N ammonium-N and nitrate-N.”

Miller added, “The combination of the data is important because some of these plots may have a different amount of growth -- it is not just the percent of nitrogen — if you have more vetch you have more total nitrogen. In Middletown, where it was cooler in the crop year 2018-19, we had less growth and, therefore, less nitrogen.”

A Technological Point of View

The research is aided by yet another assistant — an unmanned aerial vehicle (UAV) or drone. While not officially part of the study, Miller’s expertise in drone technologies lends additional data and perspective to the study. Working with a drone provides Taraila with a unique experience.

Miller’s drone, a DJI Matrice 210 equipped with Altum multispectral camera, produces Normalized Difference Vegetation Index or NDVI. The images, taken about once a week, will indicate the biomass and match that with the plots, soil tests and plant tissue results to see if there is any correlation among the data.

“So these plants growing right now at Carvel are absorbing red and reflecting green. What you can’t see here is that it is reflecting near-infrared light off of the cell walls. When a plant starts to die, it changes the amount of red near-infrared it reflects or absorbs,” Miller said. “Now we have the NDVI measurement — a picture, carbon, nitrogen and biomass. There are more indexes than NDVI, but this one is well known.”

Miller is eager for Taraila to develop this specialized skill set.

“Working with this technology broadens Jamie’s expertise when she goes for a job,” Miller added. “She has obtained her commercial drone license, she’s gaining valuable experience with GIS software and the ability to extract data. This will be great for her resume.”

Her mentors encourage Taraila to get out and in front of agriculture stakeholders. Taraila presented the study’s preliminary findings before a large audience of more than 300 at Delaware Agriculture Week.

“The corn results in Georgetown showed that cover crops themselves had no effect on yield versus no-cover crop control. However, termination timing mattered, where later termination reduced yields by 16 bushels,” Taraila reported to the audience.

Taraila also shared that in Middletown, any planting of cover crop rendered a yield benefit of 12 to 15 bushels.

Building a graduate resume

Taraila feels fortunate to have access to the wealth of knowledge of her faculty mentors Miller and Shober.

“I have learned so much from them, even in casual conversations,” Taraila said. “Both are so approachable and they take the time to break down any questions I have. I am grateful to work with people who I admire and who are leaders in their areas.”

Taraila said she appreciates the proximity to industry and opportunities afforded her to be visible and network with other farmers and agriculture professionals. In addition to presenting at Delaware Agriculture Week, she attended the Mid-Atlantic Crop School held in November in Ocean City, Maryland, a three-day event that Shober and Miller coordinate to provide continuing education credits for certified crop advisers in the region.

Taraila feels connected to the project that recognizes both the yield increases as well as the environmental benefits cover crops provide. She recently viewed a television program about agriculture run-off into the Chesapeake Bay and sees her graduate work as pertinent and timely.

“With these cover crops, we are able to take up those excessive nutrients and hold them in the soil for when they are really needed, so they are essential for preserving the surrounding environment,” Taraila said. “We definitely have a lot of variables that we need to study and factor in. Deciding on the right cover crop, or the right mixture, and the timing of when it is planted and terminated is one of the most important challenges a  farmer will make. I am proud to participate in research that will convey the best advice to farmers.”