One of them, Petar Pranjic, told reporters before they left the decision to do so was made last night.
He said they expected disgruntled farmers from other counties to join them, so that about 1,000 tractors would drive towards the capital.
This is not only about farmers, but about Croatia's 4.5 million inhabitants who spend 70 per cent of their income on food, Pranjic said.
Speaking to Hina, he said the farmers decided for head for Zagreb because they "don't agree to the hesitation" of some disgruntled farmers who yesterday gave up on the announced protest drive to the capital.
Pranjic said farmers now demanded first and foremost the resignation of Agriculture Minister Tihomir Jakovina, saying he was manipulating the public and distorting the real situation in agriculture.
Farmers have been protesting in a number of counties for 12 days, setting up road blocks. They demand the payment of more than HRK 450 million in subsidies and are unhappy with the purchase price of wheat, HRK 1.05 per kilogram, claiming it should not be below HRK 1.35.
(EUR 1 = HRK 7.5)