The protest is one of the biggest displays of frustration with Prime Minister Narendra Modi's government, which faces a tough general election due by May next year. India's 263 million farmers make up an important voting bloc.
"Farmers have been routinely committing suicide," said one of the protest leaders, Yogendra Yadav, as he marched in a crowd down a central Delhi thoroughfare.
"It's a shame that the government doesn't have any time for those who feed us," said Yadav, who leads the Jai Kisan Andolan, a farmers' group.
Low food prices, export curbs, anti-inflation policies that keep rural incomes low and a broad shift from subsidies to investment spending have all infuriated and demoralised farmers.
Core inflation in India, where farming is a mainstay for nearly half the people, has hovered around 6 percent in the past few months, but food prices have either fallen or remained stagnant.
Agriculture contributes about 15 percent to India's $2.6 trillion economy, Asia's third-largest, but employs nearly half of its 1.3 billion people.
Farmers from more than 200 groups began gathering in New Delhi on Thursday. They demanded that the government call a special session of parliament to discuss the crisis in the countryside.
"I myself know so many farmers who have committed suicide, and their families are now living in penury," said farmer Lakhan Pal Singh from the northern state of Uttar Pradesh, India's most populous state.
"The policies of the Modi administration are responsible."
Farmers have also protested in the financial hub of Mumbai, including this month when tens of thousands of farmers marched to Mumbai to demand loan waivers and the transfer of forest land to villagers.
New Delhi police deployed 3,500 personnel in the city on Friday but there was no trouble.
In October, police fired teargas and water cannons in a clash with about 50,000 farmers heading for New Delhi.
The discontent in the countryside, where 70 percent of Indians live, could erode support for Modi's ruling Bharatiya Janata Party (BJP), which won India's biggest parliamentary mandate in three decades in the last general election in 2014.
But political analysts and farm economists say Modi will find it hard to repeat that next time.
"We voted for the BJP but anti-farmer policies of the government have hit us hard," said Singh.
Last year, police shot and killed six farmers protesting against lower prices in the central state of Madhya Pradesh, which recently held a state assembly election - a neck-and-neck contest between the BJP and opposition Congress party.
The result is due on Dec. 11.
Leaders from the main opposition Congress party, as well as left-wing parties and the Aam Aadmi (Common Man) Party addressed the flag-waving protesters who converged in the historic heart of the city.
"We've been living a hand-to-mouth existence for a very long time but rising prices of seeds, diesel and fertiliser and falling prices of milk, fruits, vegetables and even staples is the last straw," said farmer Shivpal Yadav.
"If the government doesn't address the problems, we'll be back," said Yadav, from the northern state of Haryana.
(Reporting by Mayank Bhardwaj Editing by Robert Birsel)
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)