Is PotashCorp's fortunes turning around? Image source: PotashCorp.

The past quarter was a welcome break for Potash Corporation of Saskatchewan (NYSE:POT) investors, as the stock surged nearly 13% after a dismal start to the year. However, PotashCorp continues to underperform rival Mosaic Company (NYSE:MOS), thanks largely to its greater exposure to the struggling potash markets. Mosaic is concentrated on phosphates, prices of which haven't suffered as much.

Could PotashCorp's upcoming first-quarter earnings report on April 28, then, pull the brakes on its rally, given the massive headwinds facing the company? Expectations are muted, with the company itself projecting  its Q1 earnings to be between $0.10 and $0.20 per share. That translates into a massive 55% year-over-year drop even at the higher end of the range. If that sounds awful, PotashCorp may have to lower its guidance for 2016 if things in three key areas don't improve soon. Click through the following slideshow to know what they are.