North American domestic sales of crop nutrient potash soared in May, when demand from spring planting whittled down large inventories at the mine level, according to data posted on Potash Corp of Saskatchewan's website.

Domestic sales, mainly to the United States, jumped 61 percent from April to 1.062 million tonnes. Those sales were also about 59 percent higher than a year earlier.

Cold weather that lasted later than usual gave U.S. farmers a shorter time frame to apply fertilizer and sow crops like corn, resulting in a flurry of field activity in May.

Stockpiles of potassium chloride, more commonly known as potash, slid about 138,000 tonnes from April to 2.89 million tonnes.

Inventories of the crop nutrient at the mine level still stood 20 percent above the previous five-year average. Potash production edged 1 percent higher from the previous month to 1.95 million tonnes.

Spot potash prices hovered slightly above $400 per tonne.

Potash supplies piled up last year as key global consumers China and India delayed signing new supply contracts with Canpotex, the offshore marketing company owned by Potash Corp and fellow producers Agrium Inc and Mosaic Co.

Potash exports by the North American producers dropped 21 percent in May from the previous month to 1.066 million tonnes.

The Western Canadian province of Saskatchewan, where Potash Corp has its headquarters, is home to nearly half of the world's estimated reserves of potash.