Fertiliser giants Ravensdown and Ballance-Agri-Nutrients are fighting out a patent dispute in the Auckland High Court in a potential anti-monopoly case.

Ravensdown wants to patent a delivery method for nitrification inhibitors – which restrict nitrates in soil – but Ballance claims this will give its rival a monopoly on the product, and affect its 18,000 shareholders.

Ravensdown general manager Richard Christie says the company wants the patent, to protect what it believes is the best technology in the market.

“The reason we want a patent – obviously there’s a lot of research costs we’re covering - but we want to capture the benefit for New Zealand farmers.

"Otherwise the product could in fact be sold back to us, if it’s captured by someone overseas.

"We’ve already got to the first stage of the patent with the Intellectual Property Office, it’s before the courts at the moment with the appeal.

"We’re working our way through that, we’re feeling confident, but we just have to await the judge’s decision.”

Ballance refused to comment on the case, but maintains Ravensdown is trying to make widely available technology its own, and patenting the delivery method will force other producers out of the market.