"Carla, help us, we can't live on love and water," read a slogan printed on one of the vehicles, in a message for Carla Bruni-Sarkozy, a former top model who went on to a singing career.
According to the FNSEA union, 10,000 farmers and 1,200 tractors took part in Tuesday's march across Paris.
They blame commodities markets, the government and the EU for falling grain prices, rising social charges and stifling environmental regulations and paperwork.
The demonstration comes a day before European Union Agriculture Commissioner Dacian Ciolos will visit Paris. France's agriculture minister already is saying he will seek EU help to boost grain prices.
"We want to be heard," said Philippe Lequeux, who farms a 150-hectare (370 acre) property in the Aisne district of northern France, as firecrackers competed with megaphones on Paris' Place de la Republique.
"If not, we'll come back and block all of Paris."
The farmer protest was mostly limited to northeast Paris, but it was enough to disrupt the arrival of former Panamanian dictator Manuel Noriega to France, by blocking the road taking him and French officials to a Paris court where he is facing money laundering charges.
Dominique Barrau, general secretary of the FNSEA union, says grain farmers' incomes fell 51 percent last year. The union's president, Jean-Michel Lemetayer, called for intervention in commodities markets.
"What's wrong is the deregulation of markets, and not just for cereals," he said on France-3 television. Farmers are struggling to cover their costs, and may be unable to meet their debt obligations if prices don't recover, he said.
French Agriculture Minister Bruno Le Maire said after a Tuesday Cabinet meeting that he's asking the EU to intervene in markets and has "good hope" that it will result in higher prices in coming days.
Many farmers complained that even as market prices for grain are falling, the government still raised their social charges.