Water fight: Farmers strive to limit cows' environmental footprint

As nitrates creep up in some Canterbury drinking water supplies, dairy farmers are striving to limit nitrate leaching and their cows' environmental footprint by planting special crops and experimenting with new winter grazing systems. In the second of RNZ's three-part series Water Fight, Anna Sargent reports on efforts to remedy the region's water quality woes.

A gentle breeze rolls through an oat crop on Andrew Barlass' dairy farm in the foothills of Canterbury's Mt Hutt, turning the field into a shimmering ripple of green.

The long pale stems are ready for harvest but the oats have already done an important job soaking up some of the nitrogen left behind from winter grazing.

Set against a picturesque backdrop of snow-capped mountain peaks, Barlass's 900-hectare farm is home to about 1500 dairy cows.

The third-generation farmer is trying to prevent nitrate leaching and nutrient run-off with his catch crop of oats, as levels of contaminants inch up in some rural Canterbury drinking water supplies.

"I've always been interested in nature and the environment. As farmers we're out here, we're touching the soil everyday, it's the sort of the values that we have as a family that I want my children to be able to enjoy," he said.

"The catch crop is designed to soak up the nitrogen, the oats grow in cooler temperatures than grass so we can get these in August, they take up the residual nitrogen that's left in the soil and then we take that for silage later on."

A 2022 Plant & Food Research project involving Otago and mid-Canterbury farm trials found catch crops reduced soil nitrogen leaching by up to 60 percent and cut sediment run-off by about 40 percent.

Barlass was also trialling hybrid bale grazing to improve soil health and prevent cows sitting in mud that could end up in waterways.

"You take effectively hay and allow cows to graze that over winter and you don't feed it out in lines like we typically would, we just leave the bales out there, take the wrapping off them and the cows then can eat some of that. They also spread it around, lie on it and sit on it," he said.

Canterbury's dairy boom

Since 1990, Canterbury's dairy herd has increased by about 1000 per cent, to more than a million cows.

Between 2002 and 2019, nitrogen fertiliser use in Canterbury increased by 326 percent, while the area being irrigated increased by 99 percent over the same period.

An Earth Sciences New Zealand-led study published in November confirmed that Canterbury has the highest percentage of elevated groundwater nitrates in the country, following testing of 3800 rural drinking water samples from private wells between 2022 and 2024.

Researchers identified nitrate-rich cow urine as a primary cause of contaminated groundwater.

The regional council's latest annual groundwater survey shows nitrate increasing in 62 percent of the 300 test wells.

About 10 percent were found to have nitrates above the nitrate-nitrogen limit in drinking water of 11.3 milligrams per litre (mg/L), including 18 of the 58 wells in the Ashburton zone.

The Ministry of Health considers the current maximum acceptable value (MAV) for nitrate appropriate and consistent with Australia and the European Union, although some public health experts argue the drinking water limit is too high and potentially puts people at risk of pre-term birth and bowel cancer.

Canterbury Regional Council is responsible for managing land and water use, setting pollution limits, issuing and enforcing resource consents, managing water takes and designating drinking water protection zones.

Since the start of 2025, when a temporary restriction on intensive dairy conversions ended, the council has issued discharge consents that allow for a potential increase of up to 25,800 cows.

A nitrate emergency

In September councillors voted nine to seven in favour of declaring a nitrate emergency, although some branded the move a political stunt, virtue signalling and an attack on Canterbury farmers.

Council chair Deon Swiggs voted against the motion, but said he now hoped it resulted in better awareness of nitrate pollution.

"Once people have a bit more understanding of what it is, and we all have more understanding of what it is, we can work with the industry to start addressing some of the problems where there are hotspots and where there are issues," he said.

"No-one is saying that there aren't issues, so that's where we're actually also working with the industry. While we were in our election period, the CEO stood up a whole lot of CEs around the region from the industry.

"The science people are working with other scientists around the region as well to start standing up the science, start standing up the industry response so that everybody can get on the same page."

Swiggs said the council had no choice but to follow rules set at a national level and cautioned against singling out dairy farming for blame.

"Nitrate comes from all sorts of different sources. Nitrate is because people are putting nitrogen onto the soil. All land use activities, including farming for food production, use nitrate," he said.

Federated Farmers vice president Colin Hurst said the nitrate emergency declaration was unhelpful and politically motivated.

"It risks creating unnecessary panic and driving a wedge between urban and rural communities. It's a longstanding challenge, one that farmers, councils, iwi and the wider community have been actively working on for decades," he said.

Hurst said dairy farmers had been proactive in managing nitrate levels on their properties.

"They've made huge changes fencing off waterways to keep cows out, planting waterways to absorb nutrients, using less fertiliser and being a lot more precise with the fertiliser they do use. Many are also experimenting with new winter grazing systems, adjusting crop rotations and planting specific crops to reduce nitrogen leaching," he said.

"While the results take years to fully show up in groundwater, farmers are clearly stepping up and showing real leadership on this issue."

Deputy council chair Iaean Cranwell, who voted in favour of the emergency declaration, said the council could consider mandating lower dairy stocking rates - Canterbury has the highest in the country, according to Dairy NZ - but it would need to go through a planning process "hamstrung" by the upheaval of freshwater and resource management laws.

He said the government's move in July to halt all council planning work until Resource Management Act reforms were complete had further complicated its response.

"If the regulation allowed that, I'm sure that's one thing you could look at, but at this current time we cannot look at our planning regime," he said.

RNZ requested council figures showing the total area under irrigation, whether water use was declining and whether water was over-allocated in any of region's water zones.

A regional council spokesperson said it did not keep information on the area under irrigation, instead pointing to 2022 StatsNZ data showing that about 480,000 hectares of land was irrigated in Canterbury, the greatest in the country.

Water use in some surface water catchments and groundwater zones was overallocated as a result of the current regional plan, which became operative in 2015, setting allocation limits that "in many catchments, had already been exceeded", the spokesperson said.

The council was working on measuring and understanding the effectiveness of its plans, including how well nitrate reduction goals and regional plans rules were working.

'Doing the right thing by the land'

Back on the farm, Barlass takes monthly nitrate readings from his property's waterway using a portable tester supplied by his local catchment group.

While he is comfortable with his farm stream measuring nitrate concentrations ranging from 0.3 to two mg/L, Barlass said he would monitor any changes with interest.

He was also lining the stream with native swamp and mountain flax.

"If you're planting out near waterways, they act as a filter and prevent sediments from getting into the waterway. There's 100 metres of stream here, probably with 800 plants," he said.

"This stream carries on for quite a way past here and we'd like to carry that on. That will probably be a multi-decade approach.

"I think it's incumbent upon farmers to be making improvements but also we didn't know what we didn't know before, we're learning all the time and we're finding new and better ways to do things. There's a lot of work happening and I think a lot of it goes unseen."

Barlass is a member of the Mid-Canterbury Catchment Collective, a group that helps farmers carry out environmental projects and promotes good agricultural practice.

Group co-ordinator Angela Cushnie lives in Ashburton, where the regional council's groundwater survey shows 18 of the 58 wells tested exceeding the drinking water limit.

She said farmers were more interested than ever in doing the right thing by the land, including working the soil as little as possible to curb nutrient loss, catch cropping to "mop up" nitrates and pasture-based winter grazing trials.

The collective bought three portable nitrate sensors at a cost of $10,000 each for farmers testing streams, Cushnie said.

"The good part about them, as well as getting real-time data, is just how user-friendly they are. Our community is all involved in monitoring, once a month they take samples from their drains," she said.

More than three years of data had been gathered at her local waterway, the Hinds/Hekeao catchment.

Cushnie said nitrate levels remained flat at roughly 5.5 mg/L at Windermere Drain but could spike to 8 mg/L after heavy rain.

She believed the nitrate emergency declaration sensationalised a well-known problem.

"I didn't find it particularly helpful personally because it feels like it's headline-grabbing and steers us away from practical solutions," she said.

"That doesn't alter our course and in fact regulation doesn't alter our course. We carry on with what we know is going to be effective in the long term."

Victoria University freshwater ecologist Dr Mike Joy said catch crops and native planting were unlikely to off-set the amount of nitrate pollution caused by intensive dairy farming.

"Catch crops can be effective if the nitrogen is still in the soil but mostly it's already gone you're kind of too late when the catch crop goes in there and it's a very small proportion of the farm," he said.

"We need changes in the vicinity of 90 percent reduction to have healthy liveable rivers in Canterbury. Those catch crops and riparian are not going to catch enough, we're talking a few per cent at best of a much, much bigger problem. So it's kind of ambulance at the bottom of the cliff stuff."

Joy said the best solution for healthier water was a reduction in farming intensity, including fewer cows.

DairyNZ chief science and innovation officer Dr David Burger said dairy farmers had made significant improvements to freshwater management and water quality over the past 10 years.

Nationally farmers had reduced synthetic nitrogen fertiliser use by around 30 percent over the past decade, with a 22 percent reduction between 2020 and 2023 alone, he said.

"In Canterbury, OverseerFM modelling shows a 28 per cent decrease in average nitrogen loss per hectare between 2016 and 2022 (from 60.0 to 43.4 kg N/ha/yr), equating to a 9.16 per cent total reduction in nitrogen loss," he said.

Burger said a DairyNZ project from 2018 to 2023 aimed at helping dairy farmers meet nitrogen loss reduction targets showed a 44 percent reduction in nitrogen loss from baseline years to the latest available year for each farm.

Burger said 84 percent of dairy farms were now operating under a farm environment plan, up from 32 percent in 2021.

"Dairy farmers care about clean rivers, estuaries and safe drinking water. They live in these communities, raise families here and want the same outcomes as everyone else," he said.

Barlass said "polarising opinions" about nitrate contamination of groundwater were not constructive.

"We're not all enemies we're all part of the same community and to achieve great outcomes we're going to do that better together than apart," he said.

It could take decades to see the full benefits of changing biological systems, Barlass said.

"I'm a third almost fourth generation on one of our properties. I really see myself as a custodian of the land, I don't think you really ever own it. It's something that we're there to try make better and to pass on," he said.

"Hopefully one day members of my family, my children will be carrying on that legacy."

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