New environmental rules will hit the cultivation of Dutch potatoes for French fries, potato processors fear, making the Dutch partly dependent on foreign imports for their patatje met.

From this year, potatoes grown on sandy soil will have to be harvested by October 1 to prevent harmful nitrates and nitrogen compounds from entering the groundwater, in line with a European directive.

The directive states that ‘catch crops’ – fast growing intermediate crops which absorb nitrogen compounds – must be planted by that date.

This could mean the end of potato growing on sandy soil, Andries Middag, director of potato processors organisation Vavi told the AD. ‘Many potatoes are still in the ground in September and October because they have to ripen and harden, or they are no good for chips,’ he said.

The measure will affect around half the 80,000 hectares of land where potatoes are currently grown in the Netherlands, the AD said. The Netherlands has some 3,000 potato growers producing four billion kilos of potatoes for the processing industry each year.

Farmers have criticised what they call ‘growing by calendar’.

‘Government rules are telling us to live more with nature and use fewer pesticides. But growing according to a calendar is not part of that,’ potato grower Piet Evenhuis told the paper. ‘We don’t look at the calendar on the toilet door to see when to sow and when to harvest. That depends on the weather or the moisture in the ground.’

‘We have a very efficient system at the moment at the moment but there is no capacity to process huge quantities at the same time if harvests have to take place in September,’ Middag said. Many farmers do not have sheds to store the potatoes.

Limburg agriculture organisation LLTB said the measure is ‘unjust and unwise’. ‘It would be much better to measure how much nitrate is actually in the soil in each field,’ LLTB soil expert Guido Schriever said.

The measure would mean ‘an adjustment’ for some growers, an agriculture ministry spokesperson said, but that good water quality is an important goal.