Before the widespread adoption of selective herbicides by conventional growers, mechanical weeding played a key role in keeping fields weed fre
And with the continued loss of actives within the EU, along with rising herbicide resistance in key grass and broad-leaved species across the globe, mechanical weeding could be on the verge of a wide-scale resurgence in a range of crops.
Cambridgeshire-based machinery manufacturer Garford has seen a dramatic shift in demand for its mechanical weeding implements in recent years, both at home and around the world, as managing director Philip Garford explains.
“Our core business used to be with organic growers, but of late the big increase is coming from the conventional markets. “At first this was more the niche crops where herbicide authorisations were lacking, but now we are getting more and more customers growing broad-acre crops due to herbicide resistance problems,” adds Mr Garford.
There are now a few manufacturers producing precision camera-guided hoes, including Garford, French company Carre, Dutch maker Stektee and German firm Schmotzer. Garford and Stektee also make an in-row weeder that removes weeds from between rows and between plants in vegetable and salad crops, such as lettuce.
George Hall, sales and aftersales technician at Garford, says its interrow hoe works by locking a series of grid lines on the crop rows via a high-definition camera with a live image sent direct to an in-cab console.
The computer and positioning sensor then operates a hydraulic side-shift system that moves shares from side to side to keep the steel between the rows, removing weeds and leaving the crop behind. “As for performance, we can travel in a cereal crop at speeds up to 18kph,” he adds.
The in-row weeder works in a similar way, but the cameras pick out individual plants using a determined grid reference to depict each one. A rotor and tine is then hydraulically activated by the camera and positioning sensors to rotate a rotor share around each plant to remove weeds.
“We are working three to four plants a second. With a 34cm plant spacing within the row, we would be traveling at 2.5-3kph,” explains Mr Hall. It is not essential to have GPS or RTK guidance to use the weeders, as the camera technology is able to achieve sub-1cm accuracy adjacent to crop plants.
However, Mr Hall adds that drilling with arrow-straight rows is an advantage and autosteer could be a bonus for weeder operation, steering the tractor down rows and reducing operator fatigue over long days.
Garford’s Robocrop machines are bespoke built for each customer, so price can vary, but a 6m interrow machine – complete with wheel units and tines for 25cm rows, camera, computer and SD30 hydraulic Sideshift – would set you back about £30,000 (€ 34,727).
Packed with advanced technology, a four-row Robocrop InRow for salad producers comes with camera computer, self-levelling system, steering and console, wheel units with interrow sharers and in-row weeding rotors plus tines. It costs about £58,000.
The firm expects demand to keep on rising both in the UK and overseas and it is hoped further development of the technology will improve differentiation between crop and weed, allowing mechanisms to get closer to the crop to remove them without losses.
Mr Hall also believes robotics are just around the corner: “Our vision for the future would be driverless machines or operator machines with the combined use of robotics and GPS technology,” he adds.
A lack of viable herbicide options and the need to cut hand-weeding labour costs forced one Wiltshire-based salad producer to adopt Garford’s camera-guided Robocrop InRow weeder.
Chris Hayward of DJ Hayward Growers produces about 49ha of lettuce and brassica veg crops each year at Landford, near Salisbury. He says weed control is crucial for lettuce crops to keep the right market specification for colour, shape and weight.
He adds that good labour is hard to find and the available herbicides have a six-week harvest interval that stretches beyond their midsummer turnaround time of five weeks, so chemical control isn’t viable. The farm opted for an earlier electronically driven version of the Robocrop several years ago and a new hydraulic four-row Robocrop In-row arrived last year, which boasts improved cameras. It is used twice in each lettuce crop if conditions allow.
“You need hot, sunny days with a drying wind to get the best results for killing weeds. If you weed in the rain or when it is about to rain, the weeds can get going again,” says Mr Hayward.
In a wet year, when it is a struggle to use the machine, or in longer-duration crops such as red lettuce, Mr Hayward says a proportion of hand weeding may still be required to keep on top of problem species such as fat hen and chickweed.
“I also don’t like the way it can sometimes knock into plants and loosen blocks [plant roots] if ground conditions aren’t spot on, but you need to put that against the cost of labour. We would see 5-10% of plant losses, but it is worth it to keep crops clean.”
Mr Hayward adds that the lightweight Robocrop is expensive relative to other machines that are made with much more metal due to the technology on board, but the savings more than make up for the significant outlay. “With the savings on labour, we are looking to pay the machine off within five years.”
Essex-based assistant farm manager Darren Jeans has seen the yields of the organic winter wheat he looks after almost double over three years, aided by the farm’s adoption of a camera-guided hoe. Based near Colchester, the 160ha mixed unit produces just over 100ha of organic combinable crops, including winter wheat, winter and spring barley, quinoa and beans.
Weed control is carried out with a 6m Garford Robocrop, complemented by an Einbock comb harrow and a Combcut for preventing weed seed return later in the season. Mr Jeans says the Robocrop’s cameras and hydraulic side shift are incredibly accurate as it moves through the crop, even when they were drilling cereals on 12.5cm rows.
“It spots the crop and if the coulters have moved on the drill or the GPS has played up, the hoe will move within the row at speeds of about 9-10kmh and follow the lines perfectly,” he explains. “We had a real problem with wild oats last year and it could recognise the weeds and take them out, rather than the crop,” he continues.
Frequency of use in the season will vary, depending on weed burden and how quickly the crop gets away, but the farm typically uses the hoe two or three times before the crop gets too big to avoid damage.
Mr Jeans adds that dry conditions are required to maximise weed control, with the key weed species in the range of crops broad-leaved species such as docks and thistles, along with wild oats. “You can push it, but you need at least the top couple of inches to be dry. If the tyres aren’t picking up mud, you’re OK.
“Also, you have to hoe when the weeds are small. If they get away, you have to drop it in deeper and that risks damaging the crop,” he says. With the tractor running on tickover during operation, diesel use is low and this leads to low running costs. The work rate is about 28-32ha/day when the going is good.
“We have had the hoe three years now and our winter wheat yield was close to double last year, going from 1t/acre to about 2t/acre, and it is a combination of the three machines we have. “If you are struggling with blackgrass, it could definitely improve your situation. If I were a conventional producer, I’d use it,” says Mr Jeans.