Canpotex says the price will be US$70 per tonne lower than in the contract established in March 2012.
A Canpotex spokesman says the company doesn't disclose its contract pricing.
The agreement is with a subsidiary of Sinofert, China's largest integrated agriculture company and a long-time partner of Canpotex.
Canpotex is jointly owned by Potash Corporation of Saskatchewan (TSX:POT), Agrium (TSX:AGU) and Mosaic Corp. (NYSE:MOS), a U.S. company with major potash operations in Saskatchewan.
Potash is a major raw material for fertilisers that are used to stimulate plant growth, especially food crops.
Canada has one of the world's largest supplies of potash and exports much of it to other countries including the United States, China, and India.