It’s more than a decade since dairy farmers around West Coast’s Lake Brunner were faced with the blame and challenge of cleaning up the phosphorus-sensitive lake but time has unified farmers, regional council and the community.
Greg and Renee Rooney have been farming at Inchbonnie, south of Lake Brunner, for much of that time and felt the finger pointed firmly at dairy farmers for the decline in the lake’s water quality. Monitoring of the lake showed phosphorus – which usually exists as part of a phosphate molecule – was contributing to the increasing phytoplankton growth and declining water clarity.
It’s a large, deep lake covering 41 square kilometres and plunging to 109m, and being a lake it acts like a sink for everything flowing into it, including any nutrients that get washed off the dairy farms in its catchment.
The Rooneys farm 320 effective hectares that sit three kilometres from the lake shore and, typical of most farms on the West Coast, has numerous waterways dissecting it. The area gets an annual drenching of between four and six metres of rain, which flushes waterways on a regular basis but also leaches soil and carries a lot of sediment, not just from farms but from the steep bush-clad hills surrounding the valley floors. There was debate about how to measure the phosphorus loss from farms when naturally occurring erosion carried phosphorous into the lake bundled with soil.
The Rooneys are part of a group of 21 farmers in the Lake Brunner catchment who went through the confusion and frustration of being ordered to clean up their management practices at a time when few dairy farmers around the country were being asked to do the same.
So it’s been a hard, long road, but out of that confusion and frustration has evolved a dairying community with a set of workable rules that make sense and are not so onerous after all. Like so many issues, time and education on all sides led to a consensus.
“It just evolved,” Renee says. “And I think Lake Brunner farmers are in a good space now. We’ve been through the good, the bad and the ugly and we’ve had good conversations around it. The council now comprehends the rainfall here and the challenges and I think we’ve got quite a good relationship. Things happen, like a storm event and the fences go down and the cows get in the waterway. But the council realises that now.
“Plus, a lot of us have realised we just have to get on with it. We were all at different points for a while because we didn’t really understand and there was a lot of confusion about what they wanted because different people were coming to us and saying we needed to do things.
“We had to keep coming back to what the policy says and what our rules are, and how are we going to achieve it. And it all takes time and money.”
Initially, the council took the non-regulatory approach which allowed farmers to take up voluntary sustainable farm plans as part of the Best Practice Dairying Catchment. A study followed, done by DairyNZ and the Sustainable Farming Fund, and completed by AgResearch. It included trials on five different dairy farms around Inchbonnie to look at the effectiveness of different mitigation options on individual farms, in terms of phosphorus loss to the lake and the impact on profitability.
The study used the Farmax model for profitability analysis and the Overseer model to estimate the potential phosphorus loss reduction for each scenario. Options included all paddock soil-testing and only applying phosphorus fertiliser required to maintain optimal Olsen P, moving to a low solubility source of phosphorus fertiliser, changing from high-rate to low-rate application of effluent as well as changing the size of the effluent area, restricted grazing using a feedpad, wintering facilities and fencing streams.
Those five farms then signed a statement of intent and were given sustainable farm plans outlining specific requirements for each farm with deadlines for getting it done. Later, a second round of farm plans was introduced for the wider catchment.
And as daunting as it appeared in the early days, farmers are ticking off the tasks on their farm plans and Greg says they’re still making a profit out of their business.
“You can still make a profit and do alright in Inchbonnie working with these rules. They aren’t really strict rules, they’re just good practice.”
On their own farm, cow numbers have dropped from about 800 before they took it over, to 530 cows at the peak of the season. That’s a conservative stocking rate of 1.65 cows/ha which suits them fine. The milking platform also carries about 50 drystock, and 100 young stock until May when they head to their 46ha runoff.
Half the farm is heavy, wet soil and the other half stonier, dry land, so over the years they have tried higher stocking rates and come to the conclusion lower rates produce less stress for cows, people and the environment.
Renee Rooney in front of the effluent saucer.
When they installed the system, there were no accredited DairyNZ system design planners on the West Coast, so they used local companies going through the accreditation process and it has been a learning experience for everyone.
Initially, the revolving drum was placed in the middle of the concrete wall and solids blocked the hole for the liquid to flow back into the saucer. So the drum was moved further over and they’ve decided a lip needs to be built around the side of the concrete area collecting solids because of their high rainfall.
Fine sludge has been building up in the bottom of the Tasman tank even though a jet of water acts as a stirrer and Greg suspects they might need to put three jets on one side to stir the sludge more effectively.
Strong winds caused the cover to balloon initially and one night Greg threw some balage on to hold it down. Now a small bladder sits on top of the cover and during a storm he turns off the siphon that normally takes away water collected on its surface.
At one stage pressure blew a pod off and the pipe siphoned effluent from the tank, so a pressure valve has been installed to ensure it doesn’t happen again.
But each of those problems are because they’re relatively new systems in the industry and it’s a learning process for all parties, Greg says. Overall, he’s pretty impressed with their effluent system.
“I swear by the concrete saucer. Everything is contained and once it’s in there, it can’t get out unless we put it out. And having the stirrer in there means we don’t get a crust.”
The saucer works on a sensor and the Rooneys have discovered they need to slow down the rate of effluent going into the drum in summer to allow for the extra solids. Three days of effluent can be stored in the saucer which allows for breakdowns that might occur.
“We had a really wet October and the tank was full, so we turned off the sensor and let the saucer fill up. The beauty of storage is you have an option.”
It’s more complex than their old two-pond system feeding out to a travelling irrigator and so there could be more repairs and maintenance over the years. Greg says it will be interesting to judge the system five years down the track.
