Potash Corporation of Saskatchewan will temporarily shut down its six Canadian potash mines this summer for regular maintenance, a move that is expected to help whittle down larger-than-normal stockpiles of the crop nutrient.

Potash spokesman Bill Johnson said the summer shutdowns are normal, although its Cory mine will be idle for about six weeks longer than normal for additional maintenance.

Stocks of potash at Canadian mines owned by Potash Corp, the world's biggest producer of the nutrient by capacity; Mosaic Co and Agrium Inc, were collectively 20 percent larger in May than the five-year average. The supplies were built up from late 2012, when Chinese and Indian importers delayed signing new supply contracts.

With North American crop planting season over, and no second-half supply contract in place between the three producers and China, above-average production cuts may be necessary, Cowen analyst Charles Neivert said in a note.

Potash plans to idle its largest mine, Lanigan, along with Rocanville and Allan, for four weeks. Its Cory mine will be idled for 10 weeks, Patience Lake for five weeks and New Brunswick for three weeks.

Agrium intends to idle its Vanscoy, Saskatchewan, potash mine for the normal two weeks starting in the second week of August, spokesman Richard Downey said. And a Mosaic spokesman could not be reached to meet Reuter’s deadline for this article.