Police have blocked both lanes of State Highway 27 in the Waikato after a truck and trailer carrying fertiliser rolled, spilling its load.

The crash happened about 5am near the intersection with No 2 Road, 14km northeast of Morrinsville.

No other vehicles were involved and the driver received minor injuries, police said.

Diversions had been put in place, but as some of the fertiliser had been spread on the road by passing traffic, and the road was wet, police were urging motorists to take care when driving in that area.

The road could be closed for another two to three hours, police said.