Nitrate leaching rules to 'devastate farming'

02:23, May 26 2014
A map showing areas of New Zealand recording nitrate levels above 0.8mg per litre.
"RED" ZONE: A map showing areas of New Zealand recording nitrate levels above 0.8mg per litre.

IrrigationNZ has attacked the nitrate level limit set by the Ruataniwha Board of Inquiry as setting a precedent "to devastate farming".

The comment follows a recent report by HorticultureNZ saying the proposed nitrate levels for Hawke's Bay scheme were 14 times more stringent than the international standards for drinking water.

Using a map it commissioned from National Institute of Water & Atmospheric Research (NIWA), IrrigationNZ said that already 10 per cent of 622 waterways sampled exceeded the proposed limit of 0.8 milligrams a litre.

The map shows rivers in the most productive plains areas such as Southland, Canterbury, Manawatu, Taranaki and the Waikato in the "red" zone - that is, recording nitrate levels above 0.8mg/lt.

"This map helps us understand what the consequences will be if this number is set as a precedent for New Zealand's fresh waterways," IrrigationNZ's chief executive, Andrew Curtis, said.

He said the farms that produced the bulk of New Zealand's food for would be in breach of the levels and face significant reductions.

"Having to claw back to these limits will significantly impact production and will detrimentally affect local communities which rely on farming and food processing industries to provide thousands of jobs in factories," he said.

"If we are to not paralyse New Zealand's economy in the short to medium term we need to set ourselves up with achievable goals in regards to nutrient management."

NIWA scientist Dr Clive Howard-Williams said it was a "no-brainer" to see from the map that the areas recording higher than 0.8mg/lt were the high agricultural producing regions.

"They are all lowland rivers," he said.

"I'd like to see how many of these rivers would exceed the nitrate limit naturally."

He added that the river data came from 2006-2010, so did not necessarily accurately reflect their present state.

Since 2003, 1.3 million more cows have been added to the South Island dairy herd, producing enough milk to fill about 415 milk tankers a day, according to Statistics New Zealand.

"Second, the model fitting process I used is conservative, tending to under-predict at the higher end of the observed range," Howard-Williams said.

"If so, the model may underestimate the extent to which the 0.8mg/lt threshold is exceeded."

Last week, HortNZ labelled the nitrate limit as "nonsensical".

HortNZ president Julian Raine said he used the drinking water standards comparison to show how difficult it would be for growers and orchardists to work to the nutrient limits set down by the board.

''I queried the figure of 0.8 milligrams of dissolved nitrate per litre that has been quoted as the limit. I then asked a technical expert who calculated what it would mean in terms of the international standard for drinking water,'' Raine said.

Asked why the board would set such a limit, Raine said "it doesn't make sense to me''. Raine's drinking standard calculation is supported by a water quality specialist who did not want to be named. He added that the Board of Inquiry investigated other standards besides drinking water.

Raine said the suggested nitrate nutrient limits would have an impact on vegetable growers whose products were processed by companies such as Heinz Watties.

"The vegetable industry is investing in extensive research on the measurement and management of nutrients within complex rotational farming systems but we do not have all the answers today,'' Raine said.

"Our initial assessment is that limits set in the draft are likely to have a big impact on what crops can be grown and potentially the investments that large food companies may make in the region.''

Crops that would be affected include potatoes, onions and green vegetables.

Besides the issue of nutrient levels, HortNZ is also concerned about the river flows regime, which it says will not support low impact horticulture unless the dam proceeds.

Growers and orchardists would have to find other water sources, most likely deep bores, he said.

Meanwhile, Federated Farmers Hawke's Bay provincial president Will Foley said it was not certain whether the 0.8mg figure was an "absolute or aspirational target''.

"If it's aspirational with a timeline of 25 years to meet it, then I believe that in time technology will solve this - just in the way sewage treatment has been improved,'' Foley said.

He called on the board to reevaluate the evidence of experts like Niwa and the Cawthron Institute, which had been ignored perhaps not intentionally''.

Foley said the board's draft decision would have an impact on his own farming operation.

"Its draft decision means existing sheep and beef farmers and horticulturists will need a consent as our current farming methods will be deemed to be against the law under this draft decision. That is whether the dam proceeds or not. Sheep and beef farmers like me will likely need a consent just to do what we do now,'' Foley said.

The Board of Inquiry has until June 28 to make its final decision, which may determine the viability of the Ruataniwha dam.