Work is underway in the UK to develop a robotic solution to horticultural labour shortages to help secure the harvest of the country’s most valuable vegetable crop – lettuce.

Agri-tech and machinery experts and researchers have joined forces with two of the UK’s largest lettuce growers to develop a robotic solution to automate the trickiest parts of lettuce harvesting.

The ‘lettuce project’, which is part-funded by new Innovate UK, involves:

  • Grimme;
  • Agri-EPI Centre;
  • Image Development Systems;
  • Harper Adams University;
  • The Centre for Machine Vision at the University of the West of England, Bristol;
  • G’s Fresh; and
  • PDM Produce.

Around 99,000t of whole head or iceberg lettuce was harvested in the UK in 2019. With a market value of £178 million, the crop is the UK’s most valuable field vegetable.

However, access to reliable seasonal labour has been an increasing problem, exacerbated by Brexit and Covid-19 restrictions. Early indications are that a commercial robotic solution could reduce lettuce harvesting labour requirements by around 50%.

Thom Graham, vegetable specialist at lead project partner Grimme, explained sourcing labour was becoming one of the greatest challenges facing the sector.

“In addition, the rising cost of labour with no increase in retail price has squeezed margins,” he said.

“Growers are looking at solutions that can reduce labour input costs and maintain their resilience in the sector and we hope our expertise can help.”

Dermot Tobin, managing director of farming at PDM, said many businesses needed to rely on seasonal labour for harvesting lettuce.

“Nearly all the lettuce you see on UK supermarket shelves is cut by hand,” he said.

“Sourcing labour is getting really challenging and with wage inflation rising far quicker than return to grower prices, margins are really tight.

“Our industry needs to embrace robotic technology to reduce our reliance on labour so being involved in this project is of the utmost importance to our business.”

A robotic solution to horticulture’s biggest challenge

Richard Ellis, innovation and research project manager of G’s subsidiary Salad Harvesting Services Ltd., explained the process of lettuce harvesting has already evolved over the past 30 years.

Harvest, packing, date coding, boxing and palletising can all be completed in the field, within minutes of the crop being cut. However, some steps still need to be completed manually.

“The cutting process of an iceberg is the most technically complicated step in the process to automate,” he said.

As a result, this is something the project will focus on. It will seek to adapt existing leek harvesting machinery to lift the lettuce clear from the ground and grip it in between pinch belts. The lettuce’s outer, or ‘wrapper’, leaves will be mechanically removed to expose the stem.

Machine vision will then identify a precise cut point on the stem to separate lettuce head from stem.

A prototype robotic harvester will be developed for field trials in England towards the end of the 2021 UK season, in around September, then at G’s Espana.