|Beneath the surface
with David Law
Hawke’s Bay dairy farmers Kay and Roger Feather have faced challenges with their effluent pond at a pretty extreme end of the scale – and have come to the conclusion that a more biological approach is a far better long-term solution.
After spending thousands on machinery-driven solutions to de-crust their effluent pond, the addition of Slurry Bugs in 2015 has been the only successful long-term solution – and three years on, the same bugs are still keeping the pond clear.
The Feathers own Wairango Station, an 806ha Hawke’s Bay dairy farm on “environmentally fragile” land.
They built a large 6,000,000L effluent pond to meet council regulations, incorporating recommendations for special pumps and monitoring equipment, and a vertical stirrer to mitigate the poor power supply to the pond.
However, after one year the pond crust was severe. “The stirrer company said we needed a second stirrer, which cost $8000,” says Roger Feather. “We thought ‘Okay, if we have to’.”
Six months later, no progress had been made. The company suggested they needed four-six stirrers – a revelation met with disbelief by the Feathers.
The pond was dangerously close to overflowing, and with the Taharua Stream on their land, the Feathers risked a $75,000 fine.
The pond was pumped at a cost of $24,000, and six weeks later a digger was brought in to remove the crust, which had returned thicker than ever at 1m.
In March 2015, Kay and Roger considered taking a more biological approach. They met with David Law of Forward Farming Biological Consultancy and agreed to trial Slurry Bugs, under one condition: if Roger didn’t see his face reflected in the pond, he wasn’t going to pay a cent. David agreed.
The pond was pumped down as far as possible in order to reduce the initial workload required by the Slurry Bugs, and a hose system was used to soften the crust, enabling more light and oxygen into the pond – conditions the aerobic Slurry Bugs need in order to thrive and establish dominance.
Despite a promising start, the hardened state of the pond and the reluctance of farm workers to follow new practices meant results were slower than expected. In June the couple agreed to persevere for another couple of weeks.
“I hadn’t seen the pond for a while, and one day in July I came over the hill and I saw it,” says Roger. “I said: ‘Good God! That’s unbelievable!’ The pond was back to how it was when we first built it. I could see my reflection in the surface.”
Despite navigating a few more challenges, the real transformation came three weeks after the cows were dried off. With no new pathogen-filled effluent entering the pond, the Slurry Bugs were able to catch up and permanently transform the pond back into a liquefied state.
Three years on, no new Slurry Bugs have been added. David says if conditions remain ideal, the Slurry Bugs will continue to dominate and keep the pond crust-free.
“As long as the pH remains at an ideal level of around 6.3, at which beneficial bacteria thrive, and harmful chemicals are kept out of the pond, the Slurry Bugs will continue to do their job of liquefying effluent, readying it for uptake to pasture,” says David.