Canada's Agrium has extended its shopping spree to China, where it is to increase its foothold in Henfeng Evergreen, an expanding slow-release fertilizer group.

Agrium, which is already pursuing a hostile bid for US rival CF Industries, is to exercise an option to buy 50% of Hanfeng's sulphur coated urea subsidiary.

Agrium negotiated the option two years ago as part of a deal in which it paid $63m, and offered technical expertise, for a 19.6% stake in Hanfeng group, which is headquartered and listed in Toronto.

The price of exercising the option has yet to be agreed, but will reflect the subsidiary's investments over the past two years, during which it has developed a factory 50,000 tonnes of fertilizer a year, plus a "commercial rate" of interest.

The announcement came as Hanfeng revealed the resignation of its second-in-command, Tony Busseri, after three months to "pursue other interests".

The departure of Mr Busseri, who was hired to help the Toronto-listed group seal acquisitions and joint ventures, comes less than a week after Hanfeng announced the sealing of a joint venture to construct a 150,000-tonne fertilizer plant in Indonesia.

Mr Busseri joined Hanfeng, from EnGlobe, a Canadian waste company of which he was chief executive.

Hanfeng in January said that Mr Busseri's "experience in managing capital markets and growing businesses will be a valuable asset as Hanfeng pursues its objective of expanding through mergers, acquisitions and joint-ventures in China and internationally".

And Wellington West, the Canadian broker, in February cited Hanfeng's "strong management team" as one reason for issuing a "buy" rating on the group's shares.

Xinduo Yu, Hanfeng's chief executive, said on Monday that he wished Mr Busseri "the very best in his future endeavours".