Farmers staged another series of protests around the country over the weekend against the government’s plans to curb nitrogen pollution.

Dozens of tractors blockaded the junction of the A32 and A7 motorways near Heerenveen, Friesland, on Sunday, for several hours before moving on to a supermarket distribution centre in the town.

Some of the activists were dressed as the blackface character Zwarte Piet for reasons that were unclear, according to Omroep Fryslân.

Around 30 farmers blocked the access roads to Eindhoven Airport with agricultural vehicles until midnight, although the airport said disruption to traffic was minimal. Other groups picketed supermarket distribution centres in Gelderland, Overijssel and Drenthe.

The farmers are upset at plans announced last week by the agriculture minister, Carola Schouten, to restrict the amount of protein used in cattle feed in order to reduce their nitrogen emissions.

From September 1 farmers will risk fines of up to €2,500 if they exceed the proscribed levels of protein. The industry agrees that protein levels should be reduced but disputes the amount and the way the measure is being enforced.

The government has set a target of reducing ammonia output by 200 tonnes, which Schouten says will allow 75,000 new homes to be built. A judgment by the Council of State last May requires the government to limit nitrogen oxide emissions through stricter regulations for the farming, transport and construction sectors.