The march is the latest in a series of similar protests which began more than two years ago and comes months ahead of national elections in which Prime Minister Narendra Modi will seek a third term, with farmers forming an influential voting bloc.
Farmers had headed south for Delhi a day after talks between farm unions and ministers failed to secure commitments to provide minimum prices for a range of crops.
"The government has not been able to make a strong decision on anything. We thought that giving time is not suitable now," Sarwan Singh Pandher, the general secretary of Punjab Kisan Mazdoor Sangharsh Committee (KMSC), told ANI news agency.
Hundreds of farmers and their supporters were seen mobilizing on foot and in large convoys of tractors in many parts of the northern bread basket states of Punjab and Haryana.
At midday, police fired multiple tear gas rounds to disperse the marchers at Shambhu, a border crossing between Punjab and Haryana, about 143 miles north of Delhi, where many had joined the march.
Footage showed protesters trying to break through the barricades by lifting away cement blocks placed there to halt the march, as police used drones to fire tear gas rounds into the crowd. Some protesters were also detained
The outskirts of Delhi were quiet with riot control teams standing guard behind barricades on main roads leading into the national capital, where police have prohibited large gatherings.
Farm unions are seeking guarantees, backed by law, for more state support or buying of crops at a minimum price. They also want the government to honor a promise to double their income.
Agriculture Minister Arjun Munda told reporters on Monday after talks with union leaders that some issues had been resolved but more discussions were needed. "We are hopeful that we will bring solutions," he said.
India's main opposition Congress party said the government had failed the farmers. "As a result of inadequate market prices and simultaneous price increase of inputs, farmers are falling deeper into debt," Congress lawmaker Jairam Ramesh said in a social media post.
The government announces minimum prices for more than 20 crops each year, but state agencies buy only rice and wheat at these prices, which benefits only about 6% of farmers.
In 2021, when the year-long protest by farmers pushed Modi's administration to repeal some farm laws, designed to deregulate vast agricultural markets, the government said it would set up a panel to find ways to ensure support prices for all farm produce. Farmers accuse the government of going slow on that promise.
