Mar 28 2019
When Hendrik J. Viljoen, a distinguished professor of chemical and biological engineering at the University of Nebraska, was driving across Iowa, he observed that fields of soybeans were becoming more and more infested with weeds every season.
Eventually, it was discovered that a glyphosate-resistant weed, known as “palmer amaranth,” was responsible for that; this weed is now threatening crops in the Midwest.
“Dicamba” is a type of pesticide that is presently being used to control palmer amaranth. However, when this pesticide is sprayed during windy conditions, it has a tendency to drift and as a result has an adverse impact on neighboring areas, thus affecting trees and other kinds of crops.
Viljoen is a strong believer of the concept that humans’ well-being is closely associated with the health of the animals and crops within the food chain. He reported in AIP Publishing’s journal, Physics of Fluids, that he was motivated to develop a method to treat weeds on the spot and thus remove any kind of harm from pesticide drift.
A pesticide solution can be stabilized on a rotating horizontal cylinder/roller akin to a wooden honey dipper. Its stability depends on the speed at which the applicator rotates. But the roller is only one part of a bigger process, and there are some technical details regarding the roller that we’re also addressing, namely replenishing the pesticide load via wicking from a reservoir at the center of the cylinder.
Hendrik J. Viljoen, Distinguished Professor, Department of Chemical and Biological Engineering, University of Nebraska.
The way pesticides are used on plants really makes a difference. For example, pesticides can be rolled on, sprayed from the leaf top, or delivered through a serrated roller to concurrently scuff it and use the pesticide.
“We will only arrive at an optimum design if we understand how the active ingredient in the pesticide is delivered to the weed, how it enters the phloem (the plant’s vascular system that transports the active ingredient), and the efficacy of its killing mechanism,” explained. Viljoen.
In order to use the pesticide on weeds, rollers can be placed on tiny tractors or robots.
“Our current research objective is to develop a system where unmanned aerial vehicles image fields and feed the images to trained neural networks to identify the weeds,” Viljoen stated. “The information on weed species and their exact location will then be used by the robots to spot treat the weeds.”
One major discovery made by Viljoen’s team is that the required way to use the roller is to spin it so that the original velocity at the underside of the roller matches with the direction the robot is going. The team is conducting experiments to establish any uptake bias for palmer amaranth, and also investigating ways to make part of the surface of the roller serrated.
“The idea is to physically penetrate the epidermis to enhance the amount of active ingredient that’s delivered to the weed,” Viljoen stated. “To broaden our understanding, we’ve developed a mathematical model of the transport of the pesticide in the phloem.”
The importance of this study is that although there is growing pressure to yield sufficient amounts of food for the ever-increasing population, the present method is not sustainable. Today’s trend is to apply large quantities and more powerful chemicals to regulate invasive species and weeds that have developed resistance to pesticides which were effective before.
“We must minimize the impact of our practices on the environment and reduce the use of chemicals, their residues and metabolites within our food chain and on the greater ecology,” stated Viljoen. “Technologies exist that can help us achieve these goals. Precision spray technologies use artificial intelligence to identify weeds and only spray specific areas, but we can do better. We should eliminate the risk of drift and minimize exposure of crops and soil to pesticides.”
Creating a weed-specific, drift-free applicator will lead to autonomous weed control with intelligent robots.
At this stage, we can’t envision the full utility of these robots, but they offer us the opportunity to survey fields and alert us to disease breakouts, blights or nematodes. In the future, the roller—with some modifications—could also be used to deliver small RNA molecules to plants. Smaller farm operations that focus on specialized products will likely be the first adopters of the technology.
Hendrik J. Viljoen, Distinguished Professor, Department of Chemical and Biological Engineering, University of Nebraska.