Scientists may have found a way to reduce the chemical that's been blamed for the worst pollution of our waterways.
Dairy cows are a large source of increased levels of nitrogen as nitrate from their urine leaches into soil and streams.
But reducing the negative effects could be as simple as introducing a new plant into farmers pastures.
A commonly grazed weed with the ability to significantly reduce nitrogen leaching has been developed by scientists, they've called it Ecotain.
"While it will be an excellent forage plant we now know that it will be environmentally functional it also has the potential to reducing the loss of nitrogen to the environment," says Dr Glenn Judson.
- Special report: how polluted are New Zealand's rivers?
- Special report: What is being done to save New Zealand's rivers?
- Special report: Will climate change kill off NZ's rivers?
- Special report: The blame game over NZ river health
Dr Judson says it does this in four ways, by diluting an animal's urine, reducing the amount of nitrogen, delaying the release of nitrates and restricting the amount of nitrate in the soil.
Ngāi Tahu Farming operates 17 dairy farms near the Waimakariri River - they've been working with Agricom and have Ecotain in some of their pastures. They plan to have it sewn into 30 percent of their paddocks in the next four years.
"We've seen from this science there's up to 89 percent reduction from the urine patches which we know is the biggest contributing factor to Nitrogen that is leached, so I think we can safely say there's going to be a 20-30 percent reduction," says Ngāi Tahu Farming dairy general manager Shane Kelly.
Industry experts are calling the plant a game changer.
"This is relatively easy technology for farmers to take up, it adds for the nutritional benefit of the cow and there's no productivity lost and we can have a very large gain in a relatively short time," says Ecan councillor Tom Lambie.
So Ecotain is a potentially exciting weapon in the arsenal for farmers as they try to combat the problem that is nitrogen leaching.