Algorithms meet agriculture: Ph.D. student's cutting-edge research aims to boost Virginia cotton yields

Graduate student C. Brandt Tate aims to revolutionize cotton farming in Virginia. How will one person accomplish such a lofty goal? By using drones and advanced algorithms to optimize nitrogen fertilizer application, of course.

While cotton serves as a major cash crop for Virginia, nitrogen is the most limiting nutrient for lint yield in the Southeast coastal plain. Tate’s research involves using drones to collect multispectral imagery of cotton at different growth stages and developing an algorithm to evaluate nitrogen fertilizer needs specific to the region. This innovative approach aspires to either reduce farmers’ fertilizer costs or ensure adequate application to meet crop needs in the region.

As a graduate student in the Virginia Tech College of Agriculture and Life Sciences, Tate is pursuing a Ph.D. in crop and soil environmental sciences at the Tidewater Agricultural Research and Extension Center (AREC) in southeast Virginia, where he works with the Field Crops Agronomy program under the direction of Hunter Frame, associate professor and field crops agronomist.

Although Clemson University had developed an algorithm to determine nitrogen requirements for areas in the Southeast coastal plain, Frame was curious about its accuracy in the upper Southeast coastal plain. Starting in 2020, data was collected from 12 sites in Suffolk, Yale, and Newsoms, Virginia, with three sites sampled per year. These locations represent major cotton production areas in Virginia with diverse growth conditions and soil type — from fine sandy loam, loamy sand, and loamy fine sand. 

In the first year, the Clemson algorithm overestimated the nitrogen rate. To better account for environmental changes, the algorithm was adjusted in 2021 and again in 2022 to better gauge the nitrogen response curve for the upper Southeast coastal plain. 

After Tate joined the Tidewater AREC team, he took the lead on the project and continued to process data and to adjust and refine the algorithm.  As of 2024, the latest formula has an accuracy of over 80 percent, meaning that the team is close to developing a product that can effectively predict nitrogen requirements for cotton.

“There are other algorithms out there, but when applied to the Southeast upper coastal plain, they overpredict the amount of nitrogen that is needed,” said Tate. “This research will be very beneficial to regional cotton famers as they will be able to collect their own NDVI [Normalized Difference Vegetation Index] data and input it into our algorithm and get an instant nitrogen recommendation.”

This research comes with real-life challenges, such as the impact of extreme environmental conditions. Drought or very wet weather during the growing season can skew the accuracy of the algorithm. Adjustments made during data collection are expected to improve accuracy in such situations.

Passionate about integrating technology with science, Tate has a keen interest in geographic information systems (GIS), GPS, and precision ag techniques. In addition to using drones for data collection, Tate also utilizes the technology of handheld crop sensors to collect NDVI data — which measures how healthy and green plants are by analyzing the light they reflect — from research sites at five, six, and seven weeks after planting.

“Brandt was recruited for his GIS experience and knowledge to take the lead on developing a nitrogen prediction algorithm for Virginia cotton producers,” said Frame. “His passion is evident in everything he does and is why he is a leader among the research group.”

Pursuing a Ph.D. is no small feat, but for Tate, the journey has been both challenging and rewarding. Inspired by a love for academia, agriculture, and a desire to create real change, he has navigated a path filled with rigorous study, influential mentors, and now groundbreaking research.

Tate’s academic journey began in 2015 with an undergraduate degree in environmental and soil sciences from the University of Tennessee at Knoxville. After completing his bachelor’s degree in just three years, he stayed on with the university to earn a master’s degree in the same field, studying land cover changes in Knox County, Tennessee.

A second master’s degree followed at Vanderbilt University with a research focus on the anthropogenic influences on sediment in East Fork Creek, Tennessee. 

Now well into his doctoral research, three individuals stand out for Tate as pivotal mentors: his mother, Associate Professor Joanne Logan from the University of Tennessee at Knoxville, and Associate Professor Hunter Frame, his Virginia Tech program advisor.

“Dr. Frame constantly challenges me to think on my feet,” said Tate. “Being able to think critically and take initiative is essential — especially during the most hectic parts of the growing season.”

Looking ahead, Tate hopes to continue working directly with farmers.

“Unless you are out there physically planting, growing, maintaining, and harvesting these crops, you don’t have the whole picture,” said Tate. “One of my favorite parts of working in agricultural research is being able to directly interact with the growers.”

After completing his Ph.D. Tate plans to continue using his knowledge and experience to address agricultural challenges, whether through industry or academia.

“I hope my research is able to make someone’s life easier and solve problems, whether that be something small or something on a global scale,” said Tate. “I’m looking forward to any and all future collaborations. We have the opportunity to learn something new every day and I plan on doing just that, continuing to learn.”