(Inside Science) -- Chinese scientists have proposed a way to reduce the splashing of pesticides during spraying, which could cut pollution and save money. Their experiments suggest that adding a commercially available type of salt to water-based pesticides could nearly eliminate splashing. Their findings appear online today in the journal Science Advances.
The pros and cons of pesticides
Modern advancements in agriculture have vastly reshaped our world over the last few hundred years. During the 1800s, the average U.S. farmer produced enough food to feed three to five people. Today, the number is over one hundred. This drastic change occurred as the size of the average farm also grew. The combination freed up a huge portion of the population to pursue other occupations, advancing society in many different areas.
One of the most significant agricultural advancements is the use of modern pesticides, which include chemicals designed to kill invasive weeds, foraging insects or any other pests. While the use of pesticides can be dated back thousands of years, synthetic pesticides for large scale farms weren't widespread until the 20th century. Today, these pesticides enable farmers to produce large yields of crops, but also bring with them many downsides, among them food safety and environmental pollution problems.
According to Burkhard Schulz, a plant scientist from the University of Maryland in College Park, the agriculture industry does not anticipate that better pesticide chemicals will be invented in the foreseeable future. "We simply have to work with what we have," he said.
Therefore, solutions to minimize the downsides of pesticides must come from elsewhere.
"We will have to develop new [pesticide] application or crop management methods," Schulz said.
According to the Chinese researchers, up to 50 percent of sprayed pesticides are wasted due to splashing alone. This is bad for the environment, because the chemicals can contaminate the soil and water. It is bad for the farmers, because extra pesticides cost money. And it is bad for the crops, because the overuse of pesticides can promote resistance in bugs and weeds, similar to how antibiotics can create superbugs. For these reasons, Meirong Song, a materials scientist from the Chinese Academy of Science in Beijing, and her team have been searching for solutions to reduce the splashing of liquid pesticides.
No splash zones for pesticides
Song and her colleagues examined the performances of several candidate solutions by dropping them onto a piece of cabbage leaf under a microscope. They discovered that a specific type of salt called dioctyl sodium sulfosuccinate, commercially known as Aerosol OT, is very efficient in eliminating splashing. Originally developed as a laxative in the early 20th century, Aerosol OT is now widely used as an additive in many things from printer inks to pharmaceutical products. Song's team found that the chemical is effective in reducing splashing with a concentration of only one part in a hundred in the aqueous solution.
When a droplet of pure water hits a leaf, it spreads out and then shoots upward. In contrast, the Aerosol OT mixture clings onto the surface of the leaf after spreading. The different behavior is because the chemical additive changes the wetting ability of the liquid droplet. Wetting, as its name suggests, represents the ability of a liquid to maintain contact with a solid surface. A higher wetting ability can be achieved by changing certain physical properties of the liquid, such as the surface tension. The addition of Aerosol OT would be effective at reducing splashing in water-based pesticides.
"Aerosol OT can be easily washed away with water," said Zhichao Dong, a chemist from the Chinese Academy of Sciences in Beijing and one of the paper's authors. "However, in the long term, we still need to test this on different kinds of plants during different stages of their growth."
"Today a lot of the agricultural industry is working on precision agriculture, which basically means more precise application of pesticides, for example spot treating specific weeds with a specific kind of herbicide," said Schulz.
According to Schulz, the discovery by the Chinese team can help further the effort in precision agriculture and can promote more efficient and environmentally friendly farming practices.
Editor's note: Quotes from Zhichao Dong are translated from an original interview conducted in Mandarin.