Mosaic flagged "positive developments" in the phosphates sector, despite Chinese exports topping expectations, forecasting that world shipments of the nutrient, and of potash, will hit record highs in 2018.
However, the group's shares tumbled nonetheless, standing 7.2% lower at $22.40 in afternoon deals in New York, in selling attributed to disappointment at short-term guidance.
The fertilizer giant, the world's biggest producer of finished phosphate products, in its first forecast for next year pegged global phosphate shipments at 68m-70m tonnes.
That would represent an improvement on the 67.5m tonnes expected for this year, an estimate narrowed from a previous figure of 66.8m-68.3m tonnes.
"Expect record phosphate and potash shipments in 2018," Mosaic said, foreseeing potash volumes at 63.5m-65.5m tonnes, potentially overhauling the current high set in 2014.
"We are seeing positive developments in the phosphate industry following a challenging 2016," said Joc O'Rourke, the Mosaic chief executive, adding that this improvement was coming despite a surprise rise in Chinese exports of the nutrient.
"Chinese exports in the first half of 2017 have been higher than we originally estimated," Mr O'Rourke said.
"But we continue to expect China to export fewer tonnes of phosphates this year compared to last year," when volumes reached 9.5m tonnes, in turn down on the 11.6m tonnes seen in 2015.
Nonetheless, Mosaic raised to potentially above 9m tonnes its forecast for China exports this year, from a previous estimate of about 8m tonnes.
Chinese producers were scheduled to meet last weekend to set new export prices for Chinese potash, after values fell below the previous threshold of $350 a tonne.
Demand for phosphates, and potash, meanwhile, was "strong", Mr O'Rourke said, with Mosaic selling 2.58m tonnes of the nutrient in the April-to-June quarter, at the top end of the company's guidance range, and up 133,000 tonnes year on year.
The average selling price of diammonium phosphate, a benchmark phosphate product, at $336 a tonne was also at the top end of company guidance, although down $7 a tonne year on year.
Operating profits in phosphates more than doubled to $30m.
In potash, meanwhile, operating profits more than quadrupled, to $85m, helped by spending cuts, as well as a benefit from 7.4% increase to 2.19m tonne in sales volumes, with the average sales price essentially flat at $179 a tonne.
"Potash results reflect excellent cost control," Mr O'Rourke said.
Group earnings came in at $97.3m, compared with an after tax loss of $10.2m a year before, and equivalent to $0.29 per share, excluding one-off factors.
That was ahead of market expectations of a $0.23-per-share result.
However, the shares tumbled 9.0% at one point, in selling viewed as spurred by guidance that diammonium phosphate selling prices for the current, July-to-September quarter will fall back to $310-330 a tonne, and volumes ease to 2.2m-2.5m tonnes.
"Somebody's obviously selling on the future," Joc O'Rourke, the Mosaic chief executive, told Reuters, while flagging that raw material prices were on the decline, as well as sales values.
By Mike Verdin