Agricultural contractors are being reminded that they must leave a buffer of at least two metres between waterways and areas cultivated for growing maize.

Maize cultivation - involving ploughing paddocks and planting seed - happens in spring. Waikato Regional Council has been receiving reports of contractors failing to follow the two-metre rule.

"The rule is aimed at preventing sediment and nutrients in the soil from getting into waterways, as this can affect water quality and the health of aquatic organisms," said programme manager Ross Wightman.

"Following the reports of some contractors failing to maintain the right distance, all agricultural contractors in the region are being written to reminding them of their obligation.

"Farmers need to be aware of this issue to and ensure contractors are following the two metre rule," Mr Wightman said.

"If a contractor fails to observe the right distance both they and the farmer can be liable for enforcement action."