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July/August 2023 | Henny Zitha

Non-chemical forestry weeding technologies

Stand Tending


Weeds are abiotic factors which cause substantial losses in yield in forestry. The growing health effects to humans and animals as a result of herbicide and pesticides use has become a worldwide problem, hence the need to develop environmentally friendly solutions to eradicate weeds. With the growth of technology, drones and robots have been successfully adopted in agriculture for weeding. To date agriculture has been the leader in cutting edge weeding technology adoption compared to forestry. New 4IR technologies are increasingly being introduced and used to perform activities like weeding more efficiently. In forestry there has been a limited adoption of these technologies however with the issue of labour shortages, increasing costs and health and safety issues this technology adoption can become a viable solution. This article aims to concisely explore the drivers of weeding technology in forestry and existing non-chemical weeding technologies and other technologies used in agriculture which can potentially be adopted in forestry.

Drivers of weeding technology in Forestry
The use of herbicides has positive effects in weed eradication but also negative environmental impacts and thus reducing or gradually moving away from using herbicides may lessen the impacts. In some cases, existing herbicides, insecticides, pesticides have become more and more ineffective due to the evolution and spread of herbicide-resistant weeds. Chemical weeding is commonly used because it a cost effective and efficient method, however, it carries a risk of water contamination. Over the recent past, weeding technology has advanced, with some technologies that can take about 0.2 seconds to spot and spray the unwanted weeds with a targeted jet of herbicide. The forestry industry is seeking to reduce the use and dependency chemicals for weed control. Some countries do not permit the use of herbicides in forestry applications (e.g., Sweden). Technologies that can identify and target specific weeds can help to significantly reduce the quantities used for chemical weeding.

Non-chemical weeding methods used in forestry
Historically, manually intensive methods (manual slashing, hoeing and clearing) were predominately used as a weeding method prior to the increased use of mechanical methods. As technology has gained momentum forestry has adopted alternative non-chemical methods like using tractor attached implements like disking, tilling, flails, and rotavators to reduce and remove weeds.
Furthermore, brush cutters are a motor manual option which is used for weeding options in specific conditions. Mulching is also another option, even though it is primarily used for residue reduction it can be combined with a weeding operation. To date these systems are still being widely used in forestry operation, sometimes in conjunction with herbicide boom sprayers adopted from the agricultural sector.
Non-chemical sprayers
Without the use of herbicides, weeding technology is gaining popularity in agriculture with laser weeders, XPower XPR electric weeding solution, and Row Shaver to mention a few.
Laser Weeder (Carbon Robotics)
Is a robot that does not use herbicide instead uses high-powered thermal lasers that kill weeds once they have been identified by the AI-based cameras. It is fitted with 30 lasers spread 6 meters apart moreover it has an effective average weeding capacity of 0.8 ha/h. It can eliminate up to 200 000 weeds per hour when pulled along by a tractor irrespective of time of day or weather conditions. It is a fully adjustable robot and in the comfort of the cab the operator can do adjustments between crop spacing via a touchscreen. The lasers destroy weeds instantly and the burnt weeds remains are composted back into the soil. Killing weeds with lasers avoids the drift of the spray chemicals used during spraying. Using this weeding technology improves crop yield, reduces costs of farming and it supports sustainability.
Source: Carbon Robotics
XPower XPR electric weeding solution (New Holland)
The XPR is a high voltage, non-chemical weeding equipment for non-selective weed control between crop rows at competitive working speed. This features a generator and a applicator specifically adapted to the requirements of all row crops. It works up to 3.7 m working width, it is easily adjustable for different application width from 25 to 40 cm. The modular XPower design has a multifunctional supply unit compatible with other XPower solutions. The XPR inter-row solution provides a safe and effective weed management in row crops, with no negative impact on the environment, and providing a better planning reliability to farmers. The use of XPower technology in general respects the soil, fauna and carbon footprint, therefore it makes the XPR a real alternative to chemical herbicides and mechanical weed control.
Row Shaver (Attachment)
This is a custom attachment that mounts in front of self-propelled sprayer. It is equipped with a quick hitch that enables operators to switch a sprayer between the row shaver and spray boom and various blades lengths allow rows to be narrowed from 1m to 0.5m. It clears all weeds from between crop rows and for safety purposes the articulating blades cause the unit to flex if it strikes objects that are not weeds such as rocks. This attachment consists of a trimmer, which trims the weeds that are above the rows. It has floating sickle bar which glides above the crop canopy removing any unwanted weeds. This attachment helps eliminate the weeds that are herbicide resistant.

Source: rowshaver

With the growth of technology mechanical weeding is an environment-friendly method to be used both in agriculture and forestry and it is also the most important alternative to chemical weed control. Adoption of this technology in forestry is dependent on the terrain features slopes, harvesting residues etc. These non-chemical systems identified in this article can be used on relatively flat areas and are made for agricultural use, for forestry to adopt them, they would to be modified to fit forestry application.

Content References
Liu, C., Yang, K., Chen, Y., Gong, H., Feng, X., Tang, Z., Fu, D. and Qi, L., 2023. Benefits of mechanical weeding for weed control, rice growth characteristics and yield in paddy fields. Field Crops Research, 293, p.108852.