UPDATE 1-Potash shares tank as Russian miner flags price slump
* Russia's Uralkali says to stop fixing prices with partner
* Uralkali says potash prices could slump below $300/t
* Uralkali shares down 21.6 pct, K+S down 24.5 pct
* Britain's Sirius off 12 pct, Israel Chem loses 16.2 pct (Adds analyst profit estimate, updates prices, N.American stocks)
FRANKFURT, July 30 (Reuters) - The breakup of the biggest player by volume in the global potash market, a Russian-Belarusian joint venture, sent a shockwave through shares of European potash miners on Tuesday on fears of falling prices for the key fertiliser mineral.
Russia's Uralkali said it would no longer fix potash prices and volumes with Belaruskali, adding this may push global potash prices down below $300 per tonne in the second half of 2013 - a drop of more than 25 percent.
Shares in Uralkali plummeted 21.6 percent by 1106 GMT. Those of German rival K+S, the world's fourth-largest potash miner, slumped 24.5 percent to a six-year low, its biggest one-day drop ever.
One trader described the news as "a catastrophe" for K+S, while Commerzbank analyst Lutz Grueten said he would review his target price and recommendation.
"Assuming a 30 percent lower potash price would lead to a circa 50 percent cut in our K+S group EBIT (earnings before interest and tax) forecasts," Grueten said. Continued...