The New Zealand Defence Force has spent millions buying a Manawatū farm to expand its Ohakea air base.

The $6.4 million purchase price for the 99ha farm was about three times the average per hectare sale price of farmland in the area.

Groundwater near the farm on the airbase's southern boundary has recorded high levels of firefighting foam chemical contamination in NZDF investigations.

The problems with per and poly-fluoroalkyl (PFAS) chemicals had nothing to do with it, the NZDF said in a statement.

"The purchase was not PFAS related."

It needed the extra space for when new P-8 Poseidon patrol aircraft begin operating, it said.

 

"Ohakea Air Base is currently undergoing considerable redevelopment and growth.

"The property was purchased due to its strategic interest to Defence as it directly adjoins the base."

RNZ had asked the NZDF if it had bought any land at Ohakea or elsewhere because of PFAS contamination.

"There is no specific property acquisition budget in place at Ohakea and information relating to other potential Defence property acquisitions remains in commercial confidence," it said.