Arkansas team leverages microwaves to improve weed management

Nilda Burgos, professor of weed physiology and molecular biology, is the principal investigator of study investigating microwaves as a non-chemical, broad-spectrum weed control. Photo: U of A System Division of Agriculture

Scientists and engineers with the Arkansas Agricultural Experiment Station in the U.S. are investigating the use of 915 MHz microwaves to neutralise a variety of weed seeds underground. The researchers expect microwaves will be another tool for integrated weed management that is sustainable and non-chemical.

Reducing the seed bank by even 50% would be significant, explains Professor Nilda Burgos, a specialist in weed physiology and molecular biology and the study’s principal investigator. “This reduction in weed density could greatly enhance herbicide efficacy and eventually lead to decreased herbicide use.”

Traditional methods like burning effectively destroy weed seeds but pose challenges with air quality and road visibility due to smoke. Similarly, weed seed crushers are useful but ineffective on seeds already dropped or buried in the soil. In contrast, the 915 MHz microwaves used in this study can penetrate the soil to reach and neutralize weed seeds.

Preliminary research on using 915 MHz microwaves to control weedy rice was led by Kaushik Luthra, a food science post-doctoral fellow, and Griffiths Atungulu, an associate professor and agricultural engineer specializing in grain processing and post-harvest systems. The investigation began at the request of Arkansas farmer Chris Isbell, who sought non-chemical solutions for managing persistent weeds.

Interaction with water molecules

“The water molecules constantly try to align with the change in polarity of the microwaves, creating resistance and heat. The temperature rises, and the embryo of the seed is destroyed”, professor Luthra says.

Similar to a high-frequency home microwave popping popcorn, the low-frequency 915 MHz microwaves also interact with the water molecules inside and on the surface of the weed seeds but penetrate deeper in the soil than high-frequency microwaves can.

The study is supported by a nearly $300,000 Agriculture and Food Research Initiative grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture, with additional backing from The Cotton Board and Cotton Incorporated.