Canterbury farmers are being advised to wait another week before testing their irrigation pumps.
The co-ordinator of Canterbury's Rural Recovery Group, Allan Baird, says they still don't know what damage has been caused to aquifers and wells by the earthquake.
Farmers who have already tested their pumps haven't had good outcomes, he says, with cloudy or sandy water coming out.
"The aquifers have had a fair bit of a shake-up," Mr Baird says, adding that they will eventually settle down.
In the meantime, he says, farmers should organise support for when they do turn them on. He recommends having an electrician and a pumping engineer standing by.