Dairy farmers are being reminded they have until the end of next month to report their use of synthetic nitrogen fertiliser.
New rules came into effect in July last year, known as N-cap, where annual usage of synthetic nitrogen must not exceed 190 kilograms per hectare, averaged across farmers' grazed land areas.
Farmers have to report how much they used this past year by the end of next month and can do so to their regional council or through their fertiliser company.
The Ministry for the Environment guidelines describe synthetic nitrogen fertiliser as any solid or liquid substance which is more than 5 per cent nitrogen by dry weight and applied to land as a source of nitrogen nutrition for plants.