January 21, 2016
First introduced a few years ago, abrasive weeding involves blasting weed seedlings with organic grit, shot out of an air compressor at supersonic speeds. In field tests recently conducted by a team led by University of Illinois agroecologist Samuel Wortman, it was discovered just how effective the practice can be.
The process works best on transplanted crops – in which the "good" plants are bigger and more mature than the weeds sprouting around them – and in conjunction with sheets of plastic mulch. As long as they're of a species in which the growing points are located above-ground, the weed seedlings are killed when blasted apart by the grit.
That grit can be made from almost any organic material, including nut shells, corn cobs or other agricultural waste. As noted by the Illinois team, however, fertilizers such as soybean meal could also be used. This would allow farmers to combine weeding and fertilizing in one pass, although "it is still unknown whether the fertilizer would be available for plant uptake within critical windows."
In the Illinois trials, tomato and pepper plants did sustain some superficial collateral damage, but it didn't affect their marketable fruit yield. That yield was along the same lines as is achieved when weeding by hand, and was 33 to 44 percent higher than that of non-weeded control crops.
The grit was applied using a sand blaster connected to an air compressor, pulled down rows of plants by a walk-behind tractor – it can be seen in use below. Wortman and his team, however, have since developed a dedicated device which is now undergoing testing.
A paper on the research was recently published in the journal Crop Protection.
Source: University of Illinois