The two Indian customers, Iffco and Indian Phosphates Ltd, which in February agreed to buy 1.25m tonnes of diammonium phosphate from PhosChem over the following 12 months, are to purchase a further 500,000 tonnes.

"The majority of the initial volume has been shipped," a spokesperson for Mosaic, one of Phoschem's two member compankes, told Agrimoney.com.

Steve Paxton, the president of PhosChem, which is short for Phosphate Chemicals Export Association, said that the latest sale "demonstrates that demand is rebounding in global [phosphate] markets".

'Local pockets' 

Demand for phosphates was, like that for other nutrients, hard hit by last year's slide in crop prices, which tipped farmers into an economisation drive.

US phosphate prices, which topped $1,200 a tonne in spring last year, have fallen back to about $300 a tonne, data from Canada's PotashCorp - the second PhosChem member – shows.

However, in contrast to the market for potash, where producers have kept prices relatively high, the phosphate market has shown signs of revival, with reports in the fertilizer trade press of renewed Brazilian demand.

"There are local pockets we are selling product into," the Mosaic spokesperson said.

US fertilizer groups' phosphate stocks fell in June by more than one quarter to their lowest since March 2008, and to 15% below their five-year average, the PotashCorp statistics show.

North American potash stocks grew in June to about 3.6m tonnes, the highest since at least 2005, and more than twice the long-term average.

Market reaction 

Mosaic shares, which soared last week on reports that Brazil's Vale was planning a bid, closed $0.44 lower at $49.12 in New York.

Vale on Friday said that while it was interested in fertilizer assets, and was "frequently approached" by bankers suggesting deals, it had not posted any offers in response to these meetings.