DairyNZ's new guide to help farmers get the most out of wetlands

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DairyNZ has teamed up with NIWA to create a handy guide for farmers to help them make the most out of wetlands on their land.

Protecting, restoring and creating wetlands on-farm can reduce nutrient losses, decrease the impact of floods and provide a valuable habitat for native plants and animals.

DairyNZ general manager for sustainable dairy Dr David Burger was excited about the environmental potential of on-farm wetlands.

"We know that wetlands have a lot of value on-farm for improving environmental outcomes and boosting biodiversity," he told The Country Sport Breakfast's Brian Kelly.

While the concept of designing a wetland might seem simple, putting it into practice was a different story, Burger said.

"Getting it to function well is really challenging because wetlands behave in different ways depending on the landscape variables and the environmental variables - and they can be very expensive as well to put in the ground."

DairyNZ decided to fill the knowledge gap about wetlands and help farmers with practical advice on how to tackle these challenges while reducing their environmental footprint.

The new guide included information on performance, treatment rates, where to put a wetland, what to plant in it and how much it could cost.

The guide also contained a number of case studies from around New Zealand, Burger said.

"Farmers and practitioners can learn from others who have been there and tried it out."

So far, the data on the environmental benefits of wetlands was impressive, Burger said.

"Based on our numbers, we believe wetlands can reduce up to 90 per cent of the sediment load and basically halve the nitrogen losses, as well as remove half of the phosphorous losses passing through the system - assuming that the wetland is five per cent of that receiving catchment area."

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A lot of work had gone into the science behind the guide, Burger said.

"We want to give farmers confidence around the treatment potential and also for regulators because we'd love to see these wetlands taken up in regulation more and therefore we all need confidence in how they are performing."

The guide was a collaborative effort between DairyNZ and NIWA, along with regional council staff and Fish and Game New Zealand, Burger said.

"So they've all been on the journey with us and they all endorse the guide as well - so that's been really exciting."

The new guidelines highlighted that as wetlands increased from one to five per cent of a catchment area:

• Sediment removal typically increases from 50 to 90 per cent

• Nitrogen removal increases from 25 to 52 per cent in warmer zones of New Zealand

• Nitrogen removal increases from 18 to 38 per cent in cooler zones of New Zealand

• Phosphorus removal increases from 25 to 48 per cent

The new guide can be downloaded from DairyNZ's website.