Inter­view: The laser is com­ing

Merve Woll­we­ber, bio­physi­cist at Laser Zen­trum Han­nover e.V. (Hanover Laser Cen­tre) is devel­op­ing a laser-based weed­ing sys­tem.

Ms Woll­we­ber, you lead the Food + Farm­ing group at Laser Zen­trum Han­nover (LZH). What is your team work­ing on?

We are work­ing on var­i­ous con­cepts with lasers and opti­cal appli­ances in the agri­cul­ture and food pro­duc­tion sec­tor. One of these con­cepts is to use a laser against any plant we might define as a weed.

Dr. Merve Woll­we­ber

How exact­ly does it work?

The image recog­ni­tion tech­nol­o­gy we use can inden­ti­fy dif­fer­ent plants. It can dif­fer­en­ti­ate between a cul­ti­vat­ed crop and oth­er plants which can harm the crop’s growth and reduce har­vest yield. If a weed is detect­ed, a laser beam of 5 mm diam­e­ter is acti­vat­ed, which for a tenth of a sec­ond focuss­es at the plant’s growth cen­tre. The cells die off and the plant dries out.

How far along are you in the devel­op­ment process?

The idea has been around for a few decades. It was just the tech­nol­o­gy that need­ed to be devel­oped fur­ther: The arti­fi­cial intel­li­gence of the cam­era and the com­pact laser. We use a laser sys­tem with an opti­cal out­put of 100 watts, which until now we have used to treat sin­gle rows. To be able to treat sev­er­al rows at a time, we want to work with laser man­u­fac­tur­ers to devel­op more pow­er­ful sys­tems.

We ask our­selves what kind of treat­ment makes the most sense, whether we should just con­cen­trate on the area around the crop or also on the area between rows. Depend­ing on the dis­tance between the plants, one solu­tion may be to sup­ple­ment the treat­ment with oth­er meth­ods, for exam­ple with hoes. We may be able to com­bine var­i­ous process­es here. We expect the tech­nol­o­gy to be ready for use in two to three years.

What are the advan­tages?

With the help of the laser we are able get very close to the crop, even with sen­si­tive crops. We are also able to treat every plant indi­vid­u­al­ly. These lat­est devel­op­ments open an entire new world of pos­si­bil­i­ties because there is an increas­ing aware­ness of sus­tain­abil­i­ty in agri­cul­ture. If we treat a weed with less ener­gy, we inhib­it growth until the plant sprouts again. This means weeds are no longer com­pet­ing with crops and we can do more in terms of bio­di­ver­si­ty. If I want a cer­tain weed to not seed, the solu­tion may be to sim­ply stunt its growth, rather than destroy it.

In com­par­i­son: If the plant is allowed to grow, after 14 days it looks like the first plant in this row. The pic­tures on the right show its con­di­tion at the same time after it has received a full or weak­er laser dose.

Can the laser dam­age the soil?

Not at all. We only treat the plants; the laser ener­gy is absorbed by their water. The earth com­po­nents are heat­ed to the same extent as they are by the sun.

When should you use the device in the field?

The growth stage plays an impor­tant role. In very small plants, detec­tion is a chal­lenge. The more leaves we can see, the eas­i­er the iden­ti­fi­ca­tion. But the weed should not become too large: Up to the four-leaf stage we can car­ry out the treat­ment very effec­tive­ly, but when plants are larg­er, we need even more ener­gy because they are get­ting more robust. There­fore, progress across the field is sig­nif­i­cant­ly slow­er. This, in turn, means that the process is less eco­nom­i­cal.

Exact posi­tion­ing of the laser beam (high­light­ed in red for bet­ter rep­re­sen­ta­tion) on weed mod­el plants in the lab­o­ra­to­ry test stand.

How will the laser move in the field

Nat­u­ral­ly, you would think of the laser being pulled behind a trac­tor in clas­sic fash­ion. But with robots, the laser would be able to move across fields inde­pen­dent­ly. We are also con­sid­er­ing com­bin­ing the tech­nol­o­gy with a drone: With the data we can spec­i­fy the dis­tri­b­u­tion of weeds and use an intel­li­gent treat­ment strat­e­gy to deter­mine when and where treat­ment is need­ed.

How does the laser com­pare to chem­i­cal meth­ods?

A mul­ti­tude of fac­tors such as the ini­tial costs or the ener­gy and work­ing time need to be con­sid­ered. Cur­rent­ly, the ini­tial costs are still very spec­u­la­tive. What we do know, is that there is hard­ly any wear and tear and no con­sum­ables oth­er than ener­gy. In terms of ener­gy input, if we include the pro­duc­tion of the chem­i­cal agents, we work on a sim­i­lar scale. Work­ing time is, of course, influ­enced by the speeds of 2-4km/h and whether treat­ing only one row ver­sus mul­ti­ple rows at the same time. In the future, how­ev­er, we want to be able to treat up to four rows simul­ta­ne­ous­ly. The pre­req­ui­site for this is, of course, that the laser can do this. We are still in the devel­op­ment phase. As soon as auton­o­my makes its way into the field, work­ing time will no longer be such a big issue, as the device will be ready for use around the clock, no mat­ter the weath­er.

What’s up next in the project?

Tech­no­log­i­cal­ly, we now have every­thing we need to suc­cess­ful­ly start field test­ing. More specif­i­cal­ly, in veg­etable and grain pro­duc­tion, which we intend to look at 2020. Now, it is above all about recog­nis­ing the require­ments of pro­duc­ers and gath­er­ing their expe­ri­ences in order to cre­ate good, com­pet­i­tive prod­ucts in the future.