Yesterday’s announcement of the breakup of Belarusian Potash Co. (BPC) sent shares of North American potash producers tumbling by the largest dollar amounts in nearly five years. And that may just be the good news.

BPC was created eight years ago when Russia’s Uralkali and Belarusian Belaruskali formed a marketing group for the two companies’ potash production. It competed with a North American marketing group Canpotex, which markets potash fertilizer from Potash Corp. of Saskatchewan Inc. (NYSE: POT), Agrium Inc. (NYSE: AGU) and the Canadian arm of Mosaic Co. (NYSE: MOS). The two cartels controlled about two-thirds of the world’s potash production.

In at least one respect, yesterday’s departure of Uralkali from BPC may have been predictable: Russia is not a joiner. Russia always has rejected any invitation to join OPEC, even though it was one of the world’s largest producers (and now the largest). In fact, the country’s commodities producers have a long history of cutting prices to gain market share. And Uralkali’s announcement is just the most recent.

During the oil embargoes 1970s, Russian oil producers boosted production and sold their crude at relatively low prices. They did the same thing a few years ago when most of the rest of the non-OPEC countries slapped an embargo on Iranian oil.

Russian and Ukrainian wheat producers cut prices a couple of years ago in an effort to gain market share at a time that wheat prices were going through the roof.

It may be a short-term strategy, but it is one that the Russians have used with reasonable success many times. Uralkali has said that it believes that its departure from BPC will cut the price of potash by 25%, from around $400 a metric ton to $300. Potash Corp., Agrium and Mosaic have a choice: increase production and match Uralkali’s price or let Uralkali have its way.

Shares of Potash Corp. fell 17% yesterday, to $31.63 in a 52-week range of $29.00 to $44.82.

Shares of Agrium were down 5%, at $86.50 in a 52-week range of $83.33 to $115.31.

Mosaic saw its shares tumble by nearly 18%, to $43.81 in a 52-week range of $39.95 to $64.65.