By Friedrich Geiger

BERLIN--K+S AG says individual shareholders are lining up with the German potash and salt producer's institutional investors to oppose an unsolicited $9 billion takeover approach from Potash Corp. of Saskatchewan Inc.

K+S said on Monday that it had conducted a survey among its individual shareholders who hold around 30% of the stock in the company which is among a handful of global suppliers of potash, a fertilizer.

The majority of the 28% of those investors who responded said they backed management's rejection of the takeover approach, according to the company.

"The prevailing view among [individual shareholders] is in line with that taken by the overwhelming majority of institutional investors that we are in touch with, and who also welcome the rejection of the Potash Corp. proposal," said Chief Financial Officer Burkhard Lohr. Institutional shareholders own roughly 70% of the company's shares, said a K+S spokesman.

The latest salvo from K+S in its effort to protect its independence follows its announcement last Friday that it had rebuffed a second takeover approach from Potash Corp. which would offer roughly EUR7.9 billion euros ($8.7 billion), equivalent to EUR41 a share. Potash Corp made an informal, less detailed takeover approach in July, which K+S had rejected.

The takeover fight comes amid weakness in global potash prices particularly since 2013 when Russia's Uralkali pulled out of a sales partnership with Belarus. Regional sales alliances had previously kept potash prices high.

K+S and Potash Corp. both mine potash and a tie-up would create a business that could control as much as 30% of the global market.

K+S invited in mid-July all private shareholders, who together hold about 30% of the company, to participate in a survey. About 28% of them responded, it said.

Of the respondents, 84% supported the rejection of Potash Corp's takeover bid by K+S's management. Only about 4% of survey participants would sell their shares at the price Potash Corp. has proposed. A significantly higher offer would be accepted by 28% of the respondents, K+S said its survey had found.

Individual investors "share the assessment of the K+S board of executive directors and supervisory board that the current Potash Corp. proposal fails to reflect the fundamental value of K+S," said Chief Executive Norbert Steiner.

Potash Corp. Chief Executive Jochen Tilk said in late July that he believes a combination with K+S would benefit both companies. A deal would "enhance the breadth of each company's respective portfolio, improve cash flow capabilities and provide a more stable operating environment."

Potash Corp. wants to conclude a friendly acquisition of K+S and is willing to make a binding commitment to ensure that K+S operates as a separate brand and keeps its headquarters in Germany, Mr. Tilk said.

Write to Friedrich Geiger at friedrich.geiger@wsj.com

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