Organic farmers often face a dilemma when it comes to killing weeds, but a simple system using air compressors could provide an effective alternative to the many different methods currently in use.
Field tests at the University of Illinois College of Agricultural, Consumer and Environmental Sciences have demonstrated the efficiency of firing high-velocity particles at weeds, damaging them to the point at which they die off.
It’s a brute-force method that offers up to 97% effective results, and even at the lower end of the scale, at least 69% of the final mass of the weeds was removed by blasting them.
The technique has been named ‘abrasive weeding’ and, thanks to the ferocity of the air compressors used, many of the other variables simply don’t seem to matter.
Samuel Wortman, the agroecologist who tested the system, explains that walnut shells, soybean meal, greensand and granulated maize cob all offer similar results.
“When it leaves the nozzle, it’s [travelling at] at least Mach 1,” he said. “The stuff comes out so fast, it doesn’t really matter what the shape of the particle is.”
The blasting method was only used on transplanted crops, so that the stems of the crops were much better developed than the weeds – thus ensuring the crops themselves were not adversely damaged.
While some damage was seen on crop stems, the overall yield of fruit was not reduced, and was between 33-44% higher than on crops where no weeding of any kind took place.
Plastic mulch was used in combination with abrasive weeding throughout the tests, and the overall results were equivalent to those obtained through labour-intensive hand weeding.
Even better than the weeding effect alone, is the possibility to use nitrogen-rich materials as the abrasive element – thus not only reducing the prevalence of weeds in each field, but fertilising the soil at the same time.