Huge potential for integrated weed control with robots
What does the field robot mean for weed control? Could it be the solution for declining chemical options and expensive, scarce labour? To some extent, yes. “But only if carefully integrated into a broader weed management strategy,” says crop and weed specialist Timo Sprangers of Wageningen University & Research (WUR). Integrated Weed Management (IWM) is the key to reliable weed control.
An integrated approach to weeds is complex, but the potential is enormous. That is the view of Timo Sprangers, crop health researcher at WUR. By ‘complex,’ he means looking at a complete set of measures and decisions for both the short and long term. By ‘enormous potential,’ Sprangers means he is convinced that integrated approaches will significantly reduce herbicide use over time.
He even believes that sandy fields with heavy weed pressure can eventually be kept clean. “People often say there’s enough weed seed in those soils for a hundred years, so only chemicals work. I argue that with a broad strategy, even there you can reduce chemical reliance over time.”
IWM part of ICM
The discussion revolves around the role of robots in weed control. Do they replace chemical control? With herbicide resistance rising and fewer products available, chemical control is under pressure. Or are robots mainly an alternative to hand weeding in organic farming? Labour costs for hand weeding keep climbing, boosting the business case for robots. The rapid development of robotic weed systems is in itself driving adoption.
But Sprangers does not see it so one-sided. He takes a broad view and sees various weed robots as just one link in a wider strategy. That’s integrated weed management (IWM) — as part of Integrated Crop Management (ICM). And yes, that includes robots.
5 pillars of weed control in ICM
According to Sprangers, weed control within ICM rests on 5 pillars:
This means crop rotation, intercropping and strip cropping. Each crop has its specific weed problems, depending on its growing period. Some crops also offer more options to suppress weeds than others.
When choosing varieties for sugar beet or potatoes, farmers weigh leaf development speed (weed suppression) against disease resistance. “These do not automatically go together. So growers often prioritise diseases and pests. Still, keeping the crop healthy as long as possible matters. When the canopy opens up, weeds like fat hen can set seed. An integral strategy may then require extra measures, or even earlier harvesting. That costs money, but reduces weed pressure long term.” Creating a false seedbed also fits here. At WUR’s Vredepeel research farm, a trial is underway to test if a false seedbed after harvest can further lower weed pressure.
This involves deciding on ploughing or non-inversion tillage and how that affects (root) weeds. But also managing crop and weed competition for water and nutrients. “With drip irrigation and precise fertilisation, you can give the crop more of the advantage than the weeds. Site-specific management is key.”
This includes all the classic weed control methods: mechanical, chemical, thermal. This is also where weed robots, precision lasers and electrical weeders come in.
This is essentially a long-term weed strategy. What weeds are present? What is the weed pressure? What measures fit each crop? “If a field has heavy weed pressure, maybe don’t plant onions there.”
Keeping weed populations down long term
So what is the role of the weed robot? It is multi-faceted. There is a big difference between conventional and organic operations. In organic farming, robots can replace costly, hard-to-find manual labour — and remove even the last weeds to prevent future problems. In conventional systems, it’s about reducing dependency on herbicides, while knowing chemical options are still there.
“The point,” says Sprangers, “is to have a long-term strategy that keeps weed populations manageable. So eventually, you can control them with minimal effort.”
Robot for the precision work
Integrating weed robots, still a relatively new technology, requires special attention. To use a robot with a gripper or laser most effectively, farmers should handle the rougher work more conventionally — close inter-row hoeing, for example. Sprangers explains: “Then the robot can focus precisely on the crop row, keeping up some speed. The capacity for individual weed control largely depends on weed pressure. And more than ever, starting early is crucial.”
Asked how refined robotic systems can run into unexpected problems, Sprangers cites the Farmdroid. This robot sows with extreme accuracy and ‘remembers’ exactly where each seed is. It then hoes between rows and weeds within the row, avoiding seedlings. “But if you later pass with a hoe or irrigate and leave tracks, the Farmdroid can get stuck. Also, a good crop stand is essential. If beet plants fail to emerge, the robot still thinks they’re there — based on the GPS — giving weeds a chance to grow undisturbed.”
This highlights how delicate IWM already is, and how much more so when robots are added.
Weed seeds do not live forever
Returning to the idea that even heavy weedy sands or peats can be cleaned up: “Soil is not an endless seed bank,” says Sprangers. “Chickweed seed, for example, survives about 5 years in arable conditions. After 3 years, much will not germinate. With orache, serious viability drops only after about 7 years. Oily seeds last longer, but none make it a 100 years as some claim. With 100% control, natural mortality clears them out.”
“So it pays to remove even that last weed. It slows seed bank build-up. Remember a single fat hen can produce ten thousand seeds. As labour becomes a bigger issue, growers become more aware of weed pressure and want to avoid extra seed production.”
