UPDATE 1-K+S says stoppage at Bethune mine in Canada to hit Q2 earnings

* Bethune production was stopped for nearly four days

* Outage to burden operating result

* K+S working to improve below-par fertiliser quality

* Shares fall 2.8 percent (Updates share price, adds details on causes of output slippage)

BERLIN/FRANKFURT, June 19 (Reuters) - A stoppage at K+S’s new Bethune mine in Canada will weigh on the German potash miner’s second-quarter earnings, and product quality needs to be improved, its chief operating officer said in a newspaper interview, pushing its shares lower on Tuesday.

The outage of nearly four days was due to repair works at a defective boiler stack at the Bethune potash processing site and added to delays due to strikes by Canadian Pacific Railway workers.

The railway operator, which moves potash fertiliser from Bethune, Saskatchewan, to the port of Vancouver, reached a tentative agreement over employment terms with a labour union, ending the strike on May 30.

“This will burden our operating result in the second quarter,” Mark Roberts told German daily Handelsblatt.

The comments come just over a month after K+S Chief Executive Burkhard Lohr told analysts that the group was “very happy” with the development at Bethune.

K+S shares were down 2.8 percent at 0853 GMT, after dropping as much as 3.8 percent, underperforming a 1.6 percent decline by the blue-chip DAX index.

Roberts did not give details on how much impact the stoppage would have and said K+S still stood by its guidance for a significant increase in full-year earnings and a rise in sales.

A spokesman declined to comment further on the earnings forecast. He added trains moved by Canadian Pacific had been below agreed amounts for technical reasons unrelated to the strike.

Still, the company expects the Bethune mine to make a positive contribution to its annual earnings before interest, tax, depreciation and amortisation, Roberts told Handelsblatt.

Production at the mine, which went into operation last year, is now ticking along well, but the quality of the potash was still not quite as high as K+S would like, he added.

“The chemical quality of our product is certainly so good that our customers accept it,” Roberts said. “But we still need to improve the physical properties. Our engineers are working on this and I am sure that we will soon solve this issue.”

He said K+S was not planning any additional investment to improve the quality.

Reporting by Caroline Copley, Ludwig Burger and Maria Sheahan; editing by Jason Neely and Alexandra Hudson