OSLO (Reuters) -Norwegian fertiliser maker Yara on Thursday proposed to pay an extra dividend to shareholders as third quarter core earnings topped forecasts. July-September earnings before interest, tax, depreciation and amortisation (EBITDA), excluding one-off items, rose to $1.0 billion from $765 million a year ago, while analysts in a company-provided poll had expected a profit of $768 million. The board proposed an extra dividend of 10 Norwegian crowns ($0.9435) per share, and will also consider further cash returns including share buy-backs in the coming quarters, the company said in a s…