Laser Cleaning For Weed Control

Traditional weed control methods use herbicides to eliminate weeds. Herbicides can contaminate other plants and may also get into the water supply. In addition, humans and animalsmay be exposed to herbicides, and weeds may develop resistance to drugs. Another option is to replace herbicides by manual labor. The physical labor of weeding is costly and difficult to organize1.

Although it is easy to pull up between lines, it is very difficult to pull up within lines and consumes a lot of physical strength. There is a labour shortage in this area. Figure 1 Interrow and Inrow Weeding 2

 The following weed control methods available can be listed 1
· Mechanical Actuator
· Burn
· Compressed Air
· Discharge
· Frozen
· Hot Water
· Microwave
· Water Jet
· Laser
Environmentally friendly and more efficient alternative methods of weeding are needed. In this technical note, the focus is on the laser method. The idea is to use machine vision to identify a particular type of weed and then use a visible or near-infrared laser to shine pulses of the appropriate energy onto its stem to cause damage. Several researchers have looked into this idea 3,4 and found that the effectiveness of the method depends on a few parameters listed below4:
· Operating Wavelength
· Contact Time
· Spot size
· Laser Power
· Spot Location

This technique can be combined with robot machine vision and image processing to produce an effective control method. It turns out that the growth stage of a weed plays an important role in eradicating it. The earlier a weed grows, the easier it is to uproot. Accurately targeting the stem and having sufficient energy density is also important for the effectiveness of the method.

One question is which operating wavelength should be selected. In one study, a 90-watt near-infrared laser at 800 nm and a 5-watt green laser at 532 nm were used. Near-infrared laser has less surface absorption and deeper tissue penetration. At the end of the study, however, the laser was found to be more effective at destroying weeds. Two weeks after treatment, a lethal effect on weeds could be observed by observing a 90% reduction in fresh quality3.