North American demand and slower Chinese exports should support urea prices this spring, Canadian seed and fertilizer group Agrium said.
But Canadian potash miner PotashCorp forecast phosphate markets to "remain pressured" in the early part of 2016 due to weakened demand from India and Brazil.
Agrium shares fell more than 4%, as the company issued worse-than-expected full year guidance for 2016.
Chinese urea production has remained "surprisingly strong," Agrium said, despite the fact that prices are now below the cost of production for some Chinese producers.
Still, Chinese urea exports declined by 26% year-on-year in the second half of 2015.
"As a result of the continued price weakness and increased non-Chinese urea supplies, Chinese urea exports are projected to decline from 2015 levels to between 12.5 and 13.5m tonnes in 2016," Agrium said.
These dynamics should "support" the market going into the spring.
Urea prices have suffered so far this year. Batlic sea urea prices are down 18% so far this year, according to data from Credit Suisse, at $191 a tonne as of February 4.
But Chinese phosphate supplies are expected to remain relatively flat from last year's record 10.6m tonnes, Agrium said.
Phosphate prices are down 10% so far this year, Credit Suisse said, with diammonium phosphate in US gulf ports at $355 a tonne last week.
Indian fertilizer demand was expected to be "relatively low to start 2016," due to heavy inventories.
Fertilizer demand in Brazil was expected to remain "relatively flat" from low 2015 levels, as "credit constraints and the weak value of the Brazilian real" continue to pose challenges.
Granular potash prices in Brazil were down 11% last week, at $245 a tonne.
Global potash demand was seen at 58-60m tonnes in 2016, compared to 58.5m tonnes.
This is below the 59-62m tonne global potash demand forecast by PotashCorp on Tuesday.
This year will see "historically high" crop plantings worldwide, despite depressed prices, with US corn areas up as much as 3m acres, Agrium said.
"Despite the weak macroeconomic environment, we expect growers within North America and other major agricultural markets will plant historically high crop acreage again in 2016, supporting robust crop input demand," Agrium said.
"In the US, growers are expected to increase overall crop acreage, including a one to three million acre increase in corn area, as significant crop acreage was lost in 2015 due to excess moisture in parts of the US Corn Belt,"
But the autumn of 2015 saw lower than expected nutrient application in the US, due to warm weather that delayed ammonia application, and wetness that kept farmers out of the field.
"The combination of wet and warm weather meant that application equipment could not get into the field to apply crop nutrients, resulting in below-expected fall applications," Agrium said.
"The lower than expected fall applications left crop nutrient inventories at higher than expected levels throughout the supply chain and pressured prices of all crop nutrients."
"Based on expected crop acreage, North American crop nutrient demand is expected to increase by 1-3% in 2015-2016," Agrium said.
But phosphate and potash applications may miss those levels, if farmers fail to make up for slow 2015 applications over the start of 2016.
Agrium forecast 2016 earnings at $5.50-7.00 a share, below analyst's estimate of $7.03 a share.
Over the three months to December 31, Agrium reported sales of 2.41bn, down 11% year-on-year, and short of analyst forecasts of $2.85 bn.
Agrium's earnings more than tripled, to $200m, or 1.45 a share.
Adjusted earnings came in at $1.52 a share, ahead of analyst expectations of $1.38.
Agrium shares were down 2.9% at Can$113.23 in afternoon deals.