Note to reader, attached is the complete final report for FNE01-381
The goal of this grant was to create a mechanical prototype of a machine that could be pulled behind a tractor and used UV-C light to control weeds. The project was inspired by encouraging preliminary results from Denmark.
The tractor-mounted UV-C light bank proved too ambitious, and the focus of the project shifted to testing the use of UV-C lamps on test plants of various species.
The results indicate that the use of UV-C lights to control weeds is not promising.
The farmer built a frame with four UV-C bulbs that hung about three inches above the test plants. Using brassica, cucurbits, solanaceous, sunflowers, and local grasses, the farmer exposed the plants to five, 15, 30, or 60 seconds of light. After 48 hours, none of the test plants had died.
The experiment was later repeated over a three-day period when the plants were exposed to three minutes, six minutes, and then 35 minutes of UV-C. Not a single plant of any variety died.
The results were very unexpected, and the farmer has tried to establish contact with the Danish fellow who is looking for collaborator and investors for his UV-C weeder. He has not responded.
Khosla speculates that, even though her light bulbs produced the same UV-C wavelength as in the reported Danish trials, they are different bulbs and may emanate the same portion or quantity of wavelength sufficient to actually kill the plants.
The farmer also notes that the Danish bulbs produced a lot of heat, and it may have been heat that killed the plants in the Danish trials.
Another possibility is that the heat weakened the plants sufficiently to make them more vulnerable to UV-C.
“Even assuming that the bulbs I used produced only 5 percent of the UV-C light that [the Danish] bulbs produced, based on the information presented I should have been able to kill the plants several times over after 35 minutes. At the very least I should have seen some negative effects and I saw nothing whatsoever.”