A POTASH firm says new tests prove its proposed £1.5bn development will deliver major benefits.

Sirius Minerals, which wants to mine polyhalite under the North York Moors National Park, near Whitby, says a crop study programme demonstrates its product's value as a commercial fertiliser.

The firm, which says the mine could create 1,000 jobs, is working with Durham University and China's Shandong Agricultural University, as well as the Société Générale de Surveillance and NRM Laboratories on tests.

It says the studies validate previous tests on crops such as corn, cotton, oilseed rape and wheat, which prove polyhalite to be an effective fertiliser.

Bosses added Durham University's work shows polyhalite outperforms muriate of potash, a source of potassium fertiliser, in tests on young wheat growth.

Chris Fraser, Sirius' managing director and chief executive, said: “These impressive results confirm polyhalite is a valuable and effective multi-nutrient fertiliser.”

The mine, known as the York Potash Project, stalled last year when bosses deferred sending plans to the North York Moors National Park Authority to address environmental concerns.

They expect to re-submit the proposals later this year.

The company has a number of deals in place to supply polyhalite if the mine is approved.

Last week, it revealed an agreement with a US Fortune 500 agri-business to take at least 500,000 tonnes of polyhalite annually for the next five years.

It also has a deal with Sinoagri, one of China's largest fertiliser distributors, for 500,000 tonnes of polyhalite every year in a ten-year partnership.