Lobby group Farmers For Action has received thousands of pledges of support for a demonstration on Wednesday 23 March.
Coachloads of countryfolk will descend on London to highlight the sharp drop in food producers’ incomes over the last two years.
Prices for wheat, milk and pork have plunged, leaving most farmers making losses on production.
The main causes are the same as for commodities like oil or steel, with bumper global output and slowing demand in China especially.
Farmers For Action said in a statement they will protest peacefully, and aim to “open the eyes and ears of the public and the media.”
After reaching Hyde Park the marchers will deliver a letter to prime minister David Cameron at Downing Street.
Their argument is that the government has broken its promises to the support the industry, which could go the same way as British coal and steel.
“This is our opportunity to come to London and tell Mr Cameron and his government British farming is prepared to fight for its survival,” Farmers For Action said.
Over the next year incomes of dairy farmers are expected to fall another 45 per cent, while pork producers could lose 46 per cent, and arable growers could face a 24 per cent drop, according to government figures released last week.
Farmers are no strangers to protests, designed to catch the public eye.
Food producers last marched into London in July 2012, when more than 2,000 demonstrators rolled into Westminster to complain about their milk prices being slashed.
British farmers are yet to adopt the militant tactics of their French neighbours: Gallic producers have let pigs loose in supermarkets, burned tyres and looted lorries in protests that are still rumbling.