Potash prices were beginning to decline, weighed down by growing North American inventories, even before Urakali broke up the Belarusian Potash Company cartel and forecast a slump in values.
A small upturn in potash prices which began in May had gone into reverse even before Uralkali's move in late July, although they remained above $400 a tonne in the port of Vancouver, data from Canada-based PotashCorp show.
The decline in prices reflected a failure by North American producers to cut inventories despite slashing output below 1.1m tonnes in July, a drop of 22% on the previous month, and a 31% decline year on year.
However, domestic sales fell even faster, by 37% year on year to 317,000 tonnes, with the main application season past, and amid reports of a reluctance by fertilizer dealers stung by the 2008-09 collapse in values to hold more than minimal stocks.
North American exports fell 19.3% to 889,000 tonnes, allowing stocks held by the region's producers to nudge narrowly back over 3.0m tonnes, ending a spell of month-on-month declines in inventories which started in March.
The data come amid a continued discussion over prospects for potash prices following the BPC break-up, which Uralkali forecast could prompt a plunge in values below $300 a tonne.
China, the top importer, which in late-2012 agreed a supply deal priced at $400 a tonne, is said to be pressing for prices of $300 a tonne or below for new contracts for the rest of 2013 and into 2014.
India, the second-biggest importer, is believed to be seeking price reductions even on already-agreed deals.
However, some producers have cautioned over expectations of huge price cuts, with Uralkali and the remaining North American Canpotex cartel still accounting for roughly one-half of export volumes between them, implying a large concentration of selling power even without BPC.
Norbert Steiner, the chief executive of Germany's K+S, said on Tuesday that in the US, "there might be some 2%, 3%, maybe a little bit more, of price decline in the next months to come".