Tackling volunteer potatoes with Garford spot sprayer

20 years ago already, Garford was one of the first companies to offer visual cameras for the guidance of inter-row cultivators in row crops. The foundation for this was laid back in 1993 by the British Silsoe Research Institute. After its closure, the company Tillett and Hague Technology continued the developments.

As early as in 1996 (!) the system, mounted on an autonomous field robot, was able to selectively spray cauliflower plants (‘spot spraying‘). Garford has been using the same technology to detect and spray weeds and volunteer potatoes growing in crops like carrots, parsnips, onions and leeks for quite some time now, and the interest and usage requirements are spreading to general weed control in all varieties of crops. Together with Tillett and Hague, the company is currently developing a new version of its Robocrop Spot Sprayer with a different type of nozzle and more nozzles per metre.

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Demo in chicory

Future Farming had the chance to attend a demo of the Robocrop Spot Sprayer in a chicory crop in the far south of The Netherlands. Alike the previous setup, the new prototype setup is mounted in front of the tractor. The version on demo was equipped with two visual cameras to detect and follow the crop rows and detect weeds and a 2 metres wide spray boom. Wider booms are expected to follow as the previous model was available with working widths up to 12 metres.

The boom is equipped with 24 nozzles, spaced 8 cm apart. The cameras are fitted at about eye level and adjusted to see 80 cm in front of the spray boom. But it’s the camera angle that’s crucial for the effectiveness, Garford representatives say. The angle depends on the type and development stage of a crop. Once set, you’re okay for that crop/field.

Each camera sees about 1.5 metres wide which equals 3 rows of chicory. Garford say they’re still experimenting with the number of cameras for different circumstances. It concerns visual cameras that don’t actually recognise the type of weed or crop, they don’t create biomass maps and they don’t detect or measure plant chlorophyll.

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Setting according to plant width

The technology relies on row crops planted at a fixed row distance of, in this case 50 cm. It’s one of the settings you have to enter into the (non Isobus) terminal. Other required settings include the camera angle, plant height and width, plant colour and the minimum (trigger) size of weeds. The row width (50 cm) and plant width (say 10 cm) determine the bandwidth (40 cm) in which the nozzles are activated to apply an herbicide if the cameras detect any inter-row weeds. This is to prevent damage to the crop.

A wheel following the ground and measuring the operating speed triggers the timely activation of each nozzle. This is said to be more reliable than using the tractor or gps speed. The correct setting, timing actually, is crucial for hitting every weed detected.

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Speeds up to 6 kph are currently possible.

As the cameras do not recognise plants, it’s up to the operator to turn the sprayer off in time when approaching a headland or wedge. Or use gps headland control alternatively. Timing of the operation is also crucial, alike with hoeing or other herbicide applications, to avoid damage to the crop. As soon as the crop starts to close, it’s simply too late to use the Robocrop Spot Sprayer.

Apart from all previously mentioned settings, you can also set your crop’s shade of green (or other colour) and the weed(s) colour. This is valuable for targeting specific weeds like volunteer potatoes and for plant specific fungicide applications for instance.

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New type of nozzles

The machine doesn’t use common flat tip nozzles or similar, but specially developed nozzles from Tillett and Hague. Each nozzle has 6 small holes arranged in a circular pattern. The nozzles don’t work with an 80-, 90- or 110-degree angled spray pattern, but instead each hole sprays an herbicide mixture straight downward. They’re more comparable to the nozzles commonly used for applying liquid fertilisers.

The new nozzles are to better target weeds and to prevent crop damage at the same time. The tank fitted to the machine can hold up to 100 litres of spraying liquid. By adding led-lights, it should also be possible to use the spot sprayer at night.

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Eliminate at least 90% of the volunteer potatoes

The Dutch reseller of Garford estimates that the Robocrop Spot Sprayer is able to eliminate at least 90% of the volunteer potatoes present in a row crop with maximum 2% crop damage. The spot spray technology could limit the herbicide mixture usage to on average 4 litres per hectare, 50 times less than common practice. The first pre-series of the machine are supposed to become available in October this year. Pricing details haven’t yet been disclosed.