Potash stocks held by North American producers have tumbled to below their five-year average for the first time since 2008, in another sign of the sector's recovery from its 2009 slump.

Inventories held by world's biggest producers of the nutrient slid by more than 20% in February, their fourth successive month of decline, data from sector giant PotashCorp showed.

The drop left stocks at a little over 2m tonnes, 16% below their average for the previous five years.

Inventories had not fallen below the average since November 2008, as farmers began to hack fertilizer budgets in the face of falling crop markets and tighter credit, with potash suffering in particular thanks to its relatively high price.

Stocks spent much of last year at more than twice average levels, until the mothballing of half the world's potash mining capacity, and some improvement in demand as prices fell, took them into decline last autumn.

Price movements 

Potash prices held at a $350 a tonne last month for buyers loading in Vancouver, excluding freight charges.

And the data follows other signs of sector revival this year, with American producer Intrepid Potash bringing mothballed capacity back onstream, Germany's K+S announcing a pick-up in interest and PotashCorp last week raising its earnings target, after a string of profits warnings last year.

Inventories of all three major fertilizers are now below their five year averages, with nitrogen and phosphate exhibiting strong price rebounds, the briefing showed.