Here’s an irony. The humble tractor hoe, once widely used to control weeds in beet and veg crops, fell out of favour when selective herbicides became available. But now, as herbicide options dwindle, it is coming back into use.

Philip Garford from Deeping St James company Garford Farm Machinery says he is getting an increasing number of inquiries about his firm’s high-tech hoeing systems. In fact turnover is likely to increase 60% in the coming year.

“This interest has been generated by modern tractor-mounted hoes with automated electronic positioning control and outputs that enable large acreages to be covered in a reasonable amount of time.”

Mechanical hoeing has made great strides forward in recent years. There are automated steerage hoes capable of hoeing weeds between the rows and there are also versions designed to remove weeds from within the row.

The Garford Robocrop in-row hoe is sold as a single-bed 2m wide unit capable of hoeing up to five rows. It also comes in other builds that cater for a maximum of 12 rows in a three-bed system.

At its heart are two basic control systems. One keeps the hoe in line with the plants so that weeds between the rows are taken out by fixed blades. The second uses a rotating blade to remove weeds growing within the row, ie between the plants.

Both use a digital camera to provide their respective control systems with the positioning information required. To keep the hoe correctly in line so that the hoe blades are only taking weeds out – and not the crop – the camera scans the ground ahead of the hoe.

The image produced is processed to highlight the higher concentrations of green pixels relating to the crop rows. This is compared with a pre-determined grid pattern corresponding to the known crop spacing, prompting the system to lock on to the exact row centres.

Any deviation causes a signal to be sent to activate hydraulic valves to extend or retract a steering ram.

The in-row hoeing system adopted by Garford – the first of its kind – was designed and developed by electronics company Tillett and Hague Technology based at Silsoe, Bedfordshire. It uses a rotating kidney-shaped blade that, as the implement trundles forward, moves in between each of the plants to hoe the ground and then moves back out again to avoid hoeing up the oncoming plant.

To achieve this, the hoe’s control system needs to know row width, row number, disc size and the distance of the camera ahead of disc, while other information such as forward speed and plant location is gathered on the run.

Crops such as lettuce and brassicas are currently providing the biggest demand for the hoes but the range of crop types where they can be usefully used is vast – including cereals when drilled at 25cm row spacing.

“Slow-growing crops such as organic sugar beet are not quite so suitable,” he explains. “By the time the plant has emerged there are likely to be weed populations of a similar size which can make identification too difficult. The hoe could probably be used more effectively on conventional beet after the initial application of herbicide.”

On organic production systems, with their high hand-hoeing labour costs, the automated hoe could pay for itself within a year, reckons Mr Garford. He says one organic grower with 100ha (250 acres) of lettuce saved over £45,000 in labour costs in his first season – the price of his 2m Robocrop InRow.

While there are still herbicides available, it’s cheaper and more effective to continue to use them, he says. However the two techniques can be interlinked and hoeing brings soil aeration benefits too.