BLACKVILLE — Clemson University Ph.D. student Phillip Williams has received a $94,808 grant from the National Institute of Food and Agriculture to develop and test technology aimed at reducing fertilizer usage and farming operational costs.

Williams has been working with agricultural scientists and engineers at Clemson’s Edisto Research and Education Center to develop a sensor-based, variable-rate nitrogen applicator for center-pivot irrigation systems. The technology utilizes sensors, a global positioning system and mathematical calculations to optimize fertilization usage, benefitting both operational costs, crop yield and the environment. Because the applicator would work in tandem with an irrigation system, it also would save time by eliminating a second trip through the field for nitrogen applications.

Phillip Williams

Phillip Williams, who is pursuing a PhD in plant and environmental sciences, speaks to farmers about the benefits of sensor-based nutrient management.

“It will be a real-time nitrogen calculator,” Williams said. “As the center-pivot goes through the field, every few seconds sensors will calculate how much nitrogen is needed and vary the rate of nitrogen put out from that tank.”

Williams’ primary mentor on the project is precision agriculture engineer Ahmad Khalilian, who has successfully commercialized variable-rate, sensor-based irrigation technologies that have helped farmers reduce water usage.

Already, Williams and Khalilian have proven savings of up to $60 an acre in on-farm trials of a sensor-based nitrogen management method that uses a handheld optical sensor to measure nutrient content within plants. Per that method, Khalilian and Williams plant one “nitrogen-rich” strip of cotton to find the maximum or target yield. That determines the amount of nitrogen needed to reach desired yields. That information, along with sensor readings, planting date and historical yield data, is plugged into an algorithm to tell how much fertilizer should be added during side dressing, the application of nutrients in shallow bands next to growing plants.

With the two-year grant and additional funding from the South Carolina Cotton Board, Williams will expand that practice by upfitting an irrigation system with sensors developed at Clemson that can calculate nitrogen needs while passing through the field. Those sensors will communicate directly with a variable-rate nitrogen applicator connected to the irrigation system, triggering unique applications throughout the field. Williams also will test sensors developed by Clemson sensor engineer Joe Mari Maja and mounted on an unmanned aerial vehicle (UAV). The UAV will gather data the day before fertilization and create a map that will guide nitrogen applications via the irrigation system’s on-board computer system.

“With lateral irrigation systems, we can put nitrogen out even if we are not putting water out. With center-pivot irrigations, we’ll have the ability to vary our nitrogen applications along the pivot spans, for example every eight rows,” Williams said. “I think industry will pick this technology up as an option on their equipment, and if a grower wanted to go back and retrofit their system, they could do that, too.”

Williams will test the technology the next two summers on a 12-acre plot at the Edisto REC. After that, he will recruit farmers interested in participating in on-farm trials.

In three years of testing a nitrogen-management method using the optical sensor, the Clemson sensor-based nutrient management method applied 48 percent less nitrogen than farmers’ rule-of-thumb methods without affecting crop yields. Williams has conducted on-farm trials with six cotton growers in South Carolina and has shown savings of $27 to $60 an acre.

Williams said he worked with one grower who was shocked the sensor reading and algorithm informed him not to apply any fertilizer at all. The grower had planted a winter cover crop and applied poultry litter before planting. That supplied all the nutrient his cotton needed to produce, Williams said.

“I put out nothing. He put out 90 pounds an acre,” said Williams, an Orangeburg County native who expects to receive his doctorate in May 2018 in plant and environmental sciences. “At the end of the year, our yields were within a pound of each other, so he started becoming a believer.”

Approximately 9 million tons of nitrogen is applied in cotton, corn and wheat fields annually in the United States. Just a 20 percent reduction in nitrogen usage would save U.S. cotton, corn and wheat growers more than $1.8 billion annually, Khalilian estimates. There are substantial environmental benefits to reducing fertilizer usage as well. The nitrate form of nitrogen moves freely into surface and groundwater and is a significant source of water contamination.


The National Institute of Food and Agriculture (NIFA) funded this project under Grant Award No. 2017-67011-26071. Any opinions, findings and conclusions or recommendations expressed in this material are solely those of the authors and do not necessarily reflect the views of NIFA.