In a quiet corner of rural Hampshire, a robot called Rachel is pootling around an overgrown field. With bright orange casing and a smartphone clipped to her back end, she looks like a cross between an expensive toy and the kind of rover used on space missions. Up close, she has four USB ports, a disc-like GPS receiver, and the nuts and bolts of a system called Lidar, which enables her to orient herself using laser beams. She cost around £2,000 to make.

Every three seconds, Rachel takes a closeup photograph of the plants and soil around her, which will build into a forensic map of the field and the wider farm beyond. After 20 minutes or so of this, she is momentarily disturbed by two of the farm’s dogs, unsure what to make of her.

Watching her progress from a corner of the field are three people from the Small Robot Company, and the farmer who co-owns the land. Jamie Butler grows wheat – an uncertain business that can easily tip into the red. The weather is a constant source of anxiety; a hot summer like this year’s is exactly the kind of unforeseen event that can disrupt even the most careful forecasts. “If wheat was all we did,” he says, “there’s no way we’d be able to support our families.” He also keeps cows, and uses some of his land for fly fishing, “glamping” holidays, corporate awaydays and self-storage. He worries about Brexit causing a big drop in the subsidies he currently gets from Brussels.

What does he make of Rachel? “This is the revolution,” he says. And he could well be right: if the robot working in this field is the shape of farming to come, it could have dramatic implications for our food security and the natural world.

Joe Allnutt of the Small Robot Company at Meon Springs farm in Hampshire. Photograph: Graeme Robertson/The Guardian

In future, Rachel’s creators explain, robots could take care of every stage of the growing process: mapping the land, planting seeds, caring for the crop, forensically weeding, then harvesting. She may currently do only the first job, but prototypes for the other tasks will arrive over the next couple of years.

Ben Scott-Robinson, co-founder of the Small Robot Company, is a genial 44-year-old who talks about what he does with a Tiggerish enthusiasm. He is new to the world of agriculture and still surprised at what he has found. “I expected farmers to be quite luddite about the adoption of new technology,” he says, as he packs Rachel away. “Some are, but there are a load of them who understand that new things need to happen.”

If food-growers embrace this new way of farming, it will end their dependence on a ploughing process that reduces the fertility of the land, and huge tractors that not only compact the soil but restrict growing seasons to times of the year when big machines won’t get bogged down in mud. By tending crops at the level of the individual plant, robot farming will also lead to a big drop in the money farmers have to spend on pesticides. The developers claim they can increase arable farming revenues by up to 40%, and reduce production costs by as much as 60%. The agility of agricultural robots means small farms with compact fields will no longer be at a disadvantage; independent shops and restaurants will be able to grow their produce on smallholdings efficiently tended by Rachel-like machines.

‘It could be used in the wrong way. You could have entire states in the US with no one in them’

There could be equally big environmental gains. Mega-scaled agriculture often leads to the ripping out of hedgerows, to pesticides contaminating rivers and streams, and soil erosion that can exacerbate flooding. The alarming decline in the number of bees in Europe, the US and beyond is linked to the use of insecticides; the equally sobering fall in bird populations has been traced to the same source. According to its prime movers, robot farming offers alternatives to all these things, and hope of an eventual ecological renaissance.

“Many farmers’ main focus is to leave their business to the next generation,” Scott-Robinson says. “And because they go out in the fields every day, they’re aware that they’re not hearing thrushes and skylarks. They’re aware that there are not so many bees, and pollination rates are going down.”

Scott-Robinson offers them not just a cure for these problems, but a new world of profitability. So what are the downsides?

He cracks an awkward smile. “Erm… well, at the moment, we can’t see any.”

Robots that milk cows are already a reality. So are digitised systems for feeding chickens. Robots that automatically move henhouses have been used in trials to keep birds well-exercised; for pigs and cows, there is an automated machine, produced by a company in Germany, that spreads straw around the sheds where they eat and sleep (“Uniform spreading up to nine times daily gives you an optimum utilisation of the straw” promises its promotional blurb).

In the US, automated harvesting of lettuces and strawberries is starting to become commercially viable. In France, robots prune grapevines, and are used for weeding and cultivation. All over the world, food production is gradually filling up with innovations that bring a new level of care and sophistication to the rearing of livestock, and the growing of crops.

‘Small farms, big opportunity’: precision farming pioneer Simon Blackmore. Photograph: Graeme Robertson/The Guardian

What sets some of the British pioneers of robot farming apart is their ambition to mesh together the entirety of the growing cycle. This is why big financial players and institutions are starting to put money into inventions that, only four or five years ago, might have seemed laughably far-fetched: the Small Robot Company has so far attracted £1m, from sources including the government agency Innovate UK, farmers who have invested in its technology, and the crowdfunder Indiegogo.

The outfit is based in a tiny office in the bowels of Portsmouth’s Guildhall. Two long desks are strewn with wires, circuit boards and components produced on 3D printers; when she is not out in the fields, Rachel is kept on a stand near a window. Fixed to the walls are artists’ impressions of the models of robot conceived by the company’s founders for the three pre-harvest stages of wheat-growing: Tom, Dick and Harry. Tom does the same job as Rachel: according to the company’s website, he “lives on your farm and digitises your fields – he monitors them on a plant by plant basis, keeping track of the health and development of each plant”. Dick “micro-sprays each plant with fertilisers or chemicals as required to help it thrive”. Harry “places individual seeds in the ground and accurately records where he has placed them”. These three will be overseen by Wilma, the software system that “extracts the information from our crop data model, and in combination with our AI software, helps you make decisions”.

A laser bot can recognise 800 types of weed and destroy them with precision targeting

Until 2016, Scott-Robinson was working for Ordnance Survey, using drones and artificial intelligence for the detailed mapping services that bring in the bulk of its money. He was alerted to the possibilities of robotic farming by an item on Radio 4’s Farming Today programme: when he discovered there were no British startups working in the field, he decided to found one himself, and concentrate on wheat.

“Wheat is the largest crop in the world,” he says. “There are three-quarters of a billion hectares of it. It’s one of the biggest damagers of the environment, and one of the biggest areas we could improve to increase food production. And wheat makes it easy for us to go to barley, maize and corn, which are very similar in terms of the way they grow.” He says the firm is approaching the point at which its innovations can be rolled out commercially: “We are going to have a full service in the next three years. Completely ready to go. Allowing for adoption rates, within the next three years, you are going to be able to drive around and see these machines in the fields.”

At the moment, the company is a tiny operation, employing just eight people. Because its innovations uncouple food growing from big machinery and huge fields, they should – in theory – allow small- and medium-sized farms to prosper, and strip vast agribusinesses of their competitive advantage. But what happens if he eventually sells out to some multinational conglomerate?

“That’s not what we’re here for. My interest is not in starting a business to make shitloads of money and retire in five years’ time. I have no desire to make the business into something that can be sold.”

But that’s what most startups say. And most of them eventually sell out.

“That’s true, yes. But if we were taken over by someone else, the outcome could be radically different, in terms of its effect on the world.”

This is the one note of darkness that enters an otherwise optimistic conversation. “This technology could be used in a completely different way,” he says. “You could have entire states in America with no people in them. The potential for what we’re doing to be used in the wrong way is there.”

What can he do about that?

“Well, we have a very, very strong ethos within the business about what we’re trying to do. We’re here to feed the world.”

***

In Britain, a lot of the ideas behind robotic farming have emerged from Harper Adams University, a big education and research campus on the edge of Newport, in Shropshire. I drive there on a baking-hot Wednesday to meet Prof Simon Blackmore, the 64-year-old pioneer of “precision farming”. The Small Robot Company is based on his work, and he is hailed by Scott-Robinson and his colleagues as a visionary.

Joe Allnutt with Rachel, the robot he helped build: every three seconds, Rachel takes a closeup photograph of the plants and soil around her, which will build into a forensic map of the field. Photograph: Graeme Robertson/The Guardian

Blackmore has worked on the automation of agriculture for 30 years, but his big breakthrough was triggered in 2004 when the US federal government’s Department of Defense put on the first Grand Challenge, in which inventors of driverless cars were invited to try to get them along a 142-mile route through the Mojave desert. “That stirred up so many people,” he says. “The eureka moment for me was thinking, ‘What’s the Grand Challenge for agriculture?’” Over the next few years, he came up with the comprehensive seed-to-harvest concept the Small Robot Company is trying to put into practice, and started making the case for a radical transformation in the way we grow food.

One belief runs through everything he says: that farming is still stuck in the 20th-century mindset that size matters. Crops are fertilised and sprayed with pesticides en masse; harvesting takes place on an industrialised basis, which leaves no space for judging, plant by plant, a crop’s needs or readiness for harvesting. It’s hugely wasteful. Other industries such as car manufacturing have gone through revolutions that have introduced new levels of sophistication and flexibility; as Blackmore sees it, it is high time farming did the same.

He takes me on a tour of the university’s robotics lab, where he points out a crop-spraying drone he says is illegal in the UK, but is successfully used in China. He ruefully shows me a self-driving lawnmower named Tommy he says would be ideal for golf clubs, but has yet to find a commercial backer. There’s also a precision crop-spraying device called Norman (it seems no farming robot is complete without a whimsical first name). It fits inside a kitsch outer casing that looks as if it was created to break the land speed record.

As we go, he explains an ongoing project called Hands Free Hectare, now in its second year, which has successfully grown barley with no direct human involvement – using robot scouts that monitor the crop and soil, and self-driving combine harvesters – and has now moved on to wheat.

Yet the fields and sheds around the university are scattered with symbols of everything Blackmore wants to do away with: tractors, produced by the huge companies he says have so far been barely interested in his work.

“The reason why the tractor manufacturers are not developing robots is that they’re into selling big bits of metal,” he says. “Their whole mentality is, ‘The next machine’s going to be bigger than the last one.’ They’re not interested in something that’s going to disrupt them. But the startup companies aren’t concerned with continuing the things that have been done in the past – they can produce whatever they like.”

Blackmore talks about robot farming as a liberating, accessible technology. But what happens if it gets into the hands of agribusiness? What about that nightmare future of huge spaces devoid of human beings?

“Most people think this is going to be expensive, is going to do everyone out of a job and is going to be good for the big farms, not the small farms,” he says. “It’s actually the exact opposite. The big farms are all about economies of scale: big fields, big tractors. We are developing small machines. I believe the extra production we need to feed the planet is going to come from small farms that can’t use those economies of scale.”

In Asia, Blackmore points out, the average size of a farm is around one acre. “I do a lot of work in China now,” he says. “The whole southern part has many of those small farms. And they now have a big opportunity to use robots.”

The most spectacular innovation Blackmore has worked on is laser weeding. The idea is simple, but mind-boggling. A farming robot, he says, can be equipped with software that can recognise up to 800 different kinds of weed, destroying them with precision targeting. At a stroke, chemical weedkillers would become yesterday’s news.

“Everybody’s interested in it – but we’ve got the lead on it,” he says. “We can send a laser weeding robot out into the field, and you don’t need anything else to be there: it can work on a commercial farm today.” This technique has been trialled; he says it will be introduced to British farms next spring.

***

“Space robots running around the fields with lasers, killing plants,” says Paul Harter, chief operating officer of a startup called Earth Rover, based in Somerset House in London, nudging the Thames. “It’s an amazing story.” For him and the company he has worked for since 2017, it is also on the verge of becoming a reality.

Earth Rover is another company that owes its existence to Blackmore’s work. As the name suggests, its prototype robot takes some of its ideas from the British team who worked on the ExoMars rover, an automated device that will be sent to Mars in 2020 as part of a joint Russian-European project. Their aim is to use such cosmic technology in the growing of organic broccoli – with lettuce, carrots and onions to follow.

In the US, robots harvest lettuce and strawberries. In France, they prune grapevines

“Space robots are simple, robust, unlikely to break,” Harter says. “So it’s quite a good match. The idea was, ‘We’ll take this robot, improve it, and create something agricultural. We’re licensing some technology from them. Mark I was theirs, and we’ve now made Mark II. We’ve made it quite a lot cheaper.”

What do the two machines have in common? “The engineering principles – simple, mechanical solutions. If you look at how a Mars rover’s suspension works, there are no springs: everything’s just on rockers, and it uses gravity to keep the wheels stuck to the ground. Every wheel is independently steerable. So we use things like that.”

Earth Rover’s laser weeding machine will start to appear on farms next year, with the automated harvesting of broccoli following sometime around 2021. Since the EU referendum, British food-growers have already experienced labour shortages, as the people who once would have come to the UK to work in the fields have stayed at home. This may have big repercussions for broccoli, which Earth Rover claims it will soon be able to solve.

“Weeding and harvesting are the two main labour costs with broccoli,” Harter says. “If a field’s got badly infested with weeds, they put 30 or 40 people in and they literally lie down on beds being pulled slowly by a tractor, and weed for eight hours, by hand. Harvesting isn’t as arduous, but it’s still a manual process.” He pauses. “Farmers are losing whole fields of crops because of labour shortages. There’s an urgency and an appetite to automate these tasks. People are saying, ‘We need another way to do these jobs, because we’re losing the labour force we’re dependent on.’”

So if robot farming does strip some of the human element from farming, there may even be an upside. If there is a way to combine Brexit with a thriving UK food-growing industry, it might centre on small, intelligent machines zooming around the fields day and night, tending our food, quietly zapping whatever gets in the way.

• Commenting on this piece? If you would like your comment to be considered for inclusion on Weekend magazine’s letters page in print, please email weekend@theguardian.com, including your name and address (not for publication).

• This article was amended on 26 October 2018 because an earlier version said that Simon Blackmore had a stake in the Small Robot Company. Blackmore did introduce the founders of that company, and the company is based on Blackmore’s work, however he does not have a financial stake in that company. This has been corrected.