21 - 23 Jun 2022 International trade fair for laser material processing

Laser - an alternative to chemical weed control?

Research project “E&P Agro” at Technical College Münster: Students develop procedure for weed recognition

Münster/Steinfurt (29 April 2019). Chemical weed control - keyword Glyphosate - is widespread but often encounters harsh criticism for its effects on the environment. There could be another way, though. “This is in particular precise application without side effects for the environment,” says Matthias Lautenschläger, Scientific assistant of the TC Münster Laser Centre. The idea for a weed-free soil: Laser. “This is especially interesting for ecological agriculture,” Lautenschläger is sure.

Laser based weed control is part of the large-scale INTERREG project for “Electrification and Precision in Agriculture” (E&P Agro). A first student-run project at TC Münster is now finished. Seven TC students tested how a camera can recognise weeds with the help of industrial image processing and derive coordinates from it providing the targets for laser irradiation.

“It is our job to identify the growth centre of the plant,” explains Markus Stening. Only by hitting and damaging the centre of the weed we can stop the plant from growing further and ideally degenerate it. This is where image recognition comes in: It categorises the environment - weed, corn and other food crops, stones, dead plants - recognises the weed and determines the coordinates for irradiation. In theory well to handle - but in practice, parameters change like the lighting depending on the time of day, plants grow close together or overlap, leaves wither. This makes automated weed detection a complex task.

Students chose Amaranthus retroflexus (AMARE) as their research topic.  It grows all over Germany and develops resistances against herbicides. “This makes the plant so exciting,” explains Lautenschläger. For their experiments, the students used self-grown potted plants. Amaranthus retroflexus first grows two seed leaves, then step by step more stem leaves. “The growth centre is situated at the base of the leaves and this is where the irradiation should take place,” Stening explains.

 In total, the group developed three procedures to detect the growth centre of plants under 1 millimetre in height by camera. They worked intensively with programs for industrial image processing.

“The special challenge of the project was to take a picture of a rather large area and still reliably pinpoint the position of the growth centre. “The developed procedures with their high detection rates are very helpful for the project,” praises Lautenschläger.

How large the beam diameter must be and what output the laser needs, i.e. what the correct dosage is in order to combat weeds, will now be determined in the course of the project - and in future in the field, too. Therefore, an experimental field was set on the Steinfurt campus of TC Münster in April.

On the subject:  
The project „Electrification and Precision in Agriculture“ (E&P Agro) is an INTERREG project with partners from Germany and the Netherlands. Part of the project is for example to equip tractors with electric drives and to control agricultural equipment like hoes precisely with the GPS coordinates of the crop plants.  Project coordinator is Prof. Dr. Jürgen Scholz of the Department of Mechanical Engineering of the TC Münster.