Friday, July 1, 2022

Work to be done on storage

Dairy farmers are expected to build 4000 effluent ponds and spend $1.5 billion on upgrading systems in the next few years, according to DairyNZ environmental extension specialist Trevor Foley.

“In the Waikato, only 40%, or possibly less, of dairy farms have sufficient storage, so there is a lot of work to be done,” he told farmers at a DairyNZ effluent day at Otorohanga last month.

It’s estimated that there will be about 200 new effluent ponds or tanks required on Waikato dairy farms in the next few years. Farms with insufficient effluent storage will be required to build a pond or install a tank and farms with existing ponds that have not been constructed or lined correctly, or are next to waterways, could be required to build new ponds.

Foley said farmers needed to assess the highest risk in their effluent system first, working out whether it was insufficient storage, pump capacity or pressure, which could result in over-application of effluent, or lack of sufficient effluent irrigation area.

There was a lot to consider when designing a new effluent system, with farmers needing to know whether a new storage pond or tank was required, what solids separation design was best and what pond liner to use. Key factors influencing the storage required included climate, soil type, catchment area, wash water use, cow numbers and the amount of time cows spent on the yard at milking.

One key factor farmers could influence was water use, Foley said. The average water used in the wash down/cow/day was 70 litres. The average cow produced 3.5 litres of effluent/hour.

“That’s a lot of water to move a small amount of effluent,” he said. “If you can reduce that water by half, you will reduce your storage by up to 30%.”

DairyNZ has established an accreditation process for companies designing effluent systems and has also trained companies on pond construction, which it encourages farmers to use. Tools and information are available at and farmers can also approach rural professionals for help.

There were some heated questions and concerns from farmers at Otorohanga about Waikato Regional Council changes to rules and regulations, with farmers asking if there was any guarantee if they committed a large sum of money to a new effluent system the rules wouldn’t be changed.

Council programme manager Ross Wightman said the rules hadn’t changed since 1994.

“This is the best practice at the moment,” he said. “I can’t see anything changing.”

Council inspectors have been to just 100 of the 500 farms they were hoping to visit before the end of the year as part of the council’s new trial effluent monitoring system.

“So far it’s taken us a lot of time,” Wightman said. “It’s just a trial and we may stop, but I want to keep going.”

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