The Voluntary Initiative has advised that this is because the new permits, which are being brought in by the Environment Agency for the disposal of small volumes of pesticide washings, are going to cost £390 - £266 more than the current Groundwater Authorisations.
NFU groundwater consultant Mike Payne said: "This change has been expected for some time and the NFU has already persuaded the EA to delay the introduction of this new fee structure for over a year.
"If they have not done so already, farmers wishing to make disposals of pesticides or pesticide washings to land have one last chance to get their application in before the new rates apply."
All growers wanting to dispose of (spray out) dilute wastes to farmland are required under the Groundwater Regulations to hold an authorization.
Their existing Groundwater Authorisations will automatically become Environmental Permits on April 1 and they will just have to pay the annual renewal fee as normal.