Use effluent as a tool, not a waste product

Bruce and Julie Paton milk 750 cows on 265ha south of Whangarei; 300 cows are milked in autumn and 450 in spring. Patons hosted a DairyNZ effluent field day on their property late last month.

Bruce Paton says extensive use of the effluent system started 14 years ago when the couple had the opportunity to buy the neighbor’s farm and go from 240 cows to 430.

They installed a smaller pond with a view to irrigating 90ha with the liquor from the pond. But things didn’t go as planned. 

“We got some really bad advice and it was a nightmare,” Paton says. “Both sides didn’t appreciate that you’re not dealing with something that flows well, like water. Over time the effluent builds up, the rot and the corrosion sets in and then things stop working well.”

They worked with local designer Phil Dreadon to come up with a three-pond system which would allow them to irrigate over most of the farm.

The three pond system is made up of a large 7400m3 pond, smaller 4500m3 and reserve 5600m3 pond. The effluent goes into the 7400m3 solids pond, drains through the 4500m3 pond to end up in the 5600m3 pond. 

Liquor can be drawn from the first and second ponds which Paton says is done during summer when they try to empty out all three ponds. This is done to get the full benefit of the extra capacity at calving time when it was too wet to irrigate. 

“Having the ponds the size they are now is great because now we’re able to sleep at night. Once we empty them out and the weather turns wet we are able to just get on with things.”

While most other farmers only have one effluent irrigation line going out from the pond, Patons have three. Two of the lines feed liquor out to one of two four-irrigator pod systems while the other goes to a travelling irrigator.

Having three individual pipelines means Paton is able to continuously spread liquid from the pond over the farm, even if there is a problem with part of the system. “It’s just a matter of flicking over a switch when you drive by with the bike; it means that effluent can be spread over one part of the farm while we are moving other sprinkers.”

Paton says it was difficult to empty out the ponds with one irrigator but that changed once he added irrigator pods to the system. “With just the travelling irrigator it was impossible to keep on top of effluent pond levels. It was too easy for the irrigator to break down. With the pods we can keep irrigating all the time.”

Flexibility is a big part of the system’s success and Paton says they were careful not to even bury any pipes until they were sure the system was going to work the way they wanted it to. 

“Until you actually get the effluent through the system you don’t know what the drag will be on the system and you don’t know how the irrigator will react.”

They still have a great deal of flexibility built into the system – handy when machinery breaks down. “The effluent pump broke down the other day and I was able to bring a PTO pump in and keep the system going.”

The malfunctioning pump was spotted by a staff member who worked out something was wrong when the pump was working hard yet the level of the pond wasn’t dropping. 

Ensuring staff are familiar with the workings of the effluent system minimises maintenance downtime and allows the farm to reap the most rewards from the effluent. “The key is everybody’s looking at the ponds and everybody is aware of it so if there’s a problem we know about it straight away.”

They have been able to produce 913kgMS/ha (322kgMS/cow) for the season and the liquid from the pond has kept the irrigated sections of the farm green throughout the drought.

“People notice how green it’s been at the front of the farm. I even got a phone call and was asked if I was irrigating out of the creek but I’ve just been using the last of my liquor.”