Exhibitors at the annual Waikato effluent expo at Mystery Creek are hoping the drought afflicting the region won't dry up farmer spending for them as well.
More than 40 exhibitors displayed the latest technology for managing and spreading effluent on dairy farms on Tuesday.
Waikato Regional Council, which organised the event, says about 500 farmers came to each of the first two expos and it expected at least as good a turnout this time.
But the council's environmental farming systems manager, Alan Campbell, says it's uncertain how the drought will influence farmer spending on upgrading effluent systems.
"There's a significant investment for a lot of people to make and at a time when their production is down and they're not quite sure when their grass is going to grow again, committing to spending a lot of money now is going to be a challenge to a lot of farmers."
On the cost, Mr Campbell gave as an example a farmer running a seminar at the expo, who has 800 cows and has just invested $230,000 on his storage pond, solids separator and associated ponds.
However, Mr Campbell says farmers who have plenty of effluent storage capacity are at an advantage during droughts.
He says it can be a resource waiting to be used in such periods.