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A project aimed at determining how Tukituki catchment farmers will operate under new nitrogen leaching targets has found significant changes will have to made to achieve the reduced levels.

The Hawke's Bay Regional Council's Plan Change 6 outlines Land Use Capability (LUC) nitrogen leaching rates for all farms, depending on their physical characteristics and attributes, that have to be achieved by May 2020.

Farmers unable to reach these rates could apply for resource consents provided they stay within 30 per cent of the prescribed rate.

Dubbed 'Greening Tukituki', the project began late last year and involved two dairy farmers and two sheep and beef or feedlot farmers in the Tukituki valley catchment, aimed at helping farmers find ways to reach the new targets.

When it began, the project found nitrogen-leaching rates on the four farms ranged from 7-191 per cent above the new allowance, and regular meetings had been held over the past six months to investigate their operations, said project leader and MyFarm consultant Rachel Baker.

For Takapau-based feedlot farmer and agricultural contractor Rob Foley, data showed the major contributors to nitrogen loss were the 1100 dairy cows he grazed for other Tukituki farmers on his free-draining flats in winter.

Baker said the problem with dairy cows was that their urine flow was more forceful and the nitrogen more concentrated. In comparison bull urine was less concentrated and/or dispersed more widely.

Rather than conducting expensive bore testing to determine the exact amount of leaching, Foley decided to remove the dairy cows and replace them with half the number of bulls.

This resulted in reducing nitrogen loss from 41 to 36kg nitrogen per hectare per year, but still well above the target rate of 23kg.

Environmental consultant Colin Tyler had been working with Foley and said cows were not the only contributor, that the crops also played a part.

"Data shows that the 7 per cent of this property in a rotation containing winter wheat was contributing to 38 per cent of the nitrogen leaching total.

"This is not just a livestock problem, it's crops as well. And meeting these targets is going to be very hard for these arable guys too."

While glad the study had identified measures he could take to reduce his impact on the environment, Foley said he was worried about the implications for the dairy farmers that he used to offer grazing to.

"Where will those cows go in winter? Who is prepared to take that on that cost?"

At the other end of the Tukituki catchment, Ashley Clinton dairy farmers Andy and Robbie Hunt were finding it challenging to bring their 120 year old, 123ha farm milking 330 cows within 30 per cent of its leaching rate target of 21kg of nitrogen per hectare per year.

Environmental consultant Dr Debbie Care, who mapped the farm's soils and topography and modelled different scenarios for the operation said this was frustrating.

"It's not like Andy is pushing this land to its limit. He has a low stocking rate and he doesn't use much nitrogen. He's right up there with best-practice models – he's a very good farmer."

Hunt said solutions such as building a herd home to remove the cows from wet paddocks would require an investment of at least $600,000 with no guarantee he would obtain a consent.

"I'd like to know if we will get a consent. It's likely that we are going to be 40 per cent over our LUC rate with current measurement systems – will the council give us a consent at that? Or should I just shut up shop now and walk away?"

The next stage of the Greening Tukituki project would assess the economic and social impact of the proposed solutions for each farm.