April 30 (Reuters) - Fertilizer maker Mosaic Co said on Tuesday that Saudi Arabia's flagship mining firm Ma'aden would acquire the U.S.-based company's stake in a phosphate production joint venture by issuing shares worth about $1.5 billion.

Ma'aden will issue about 111 million shares to buy the 25% stake Mosaic owns in Ma'aden Wa'ad Al Shamal Phosphate Co, a joint venture between Mosaic, Ma'aden and Saudi Basic Industries Corp.

Mosaic had said in February that a lot of the cash generated from the asset had gone into reducing debt and investing in the joint venture was not at the top of its priority.

The phosphate producer curtailed output after fertilizer prices dropped last year due to lukewarm demand from key markets.

The deal is expected to close by the end of this year. (Reporting by Sourasis Bose in Bengaluru; Editing by Savio D'Souza)