With the world's biggest fertilizer firm reporting earnings, I figured it's a good time to check in on the sector.

No, Potash Corp of Saskatchewan (NYSE:POT) hasn't reported yet. I'm talking about the biggest company by sales, not market capitalization.

Yara International is the Nokia (NYSE:NOK) of nitrogen. The Norwegian powerhouse commands around 7% global fertilizer market share. Like Agrium (NYSE:AGU) and CF Industries (NYSE:CF), Yara is enjoying tremendous demand for its nitrogen products. Costs -- 70%-90% owing to natural gas, depending on the product -- are rising, but high demand from the world's agricultural end-users has lifted fertilizer prices at an even faster clip.

As with fertility goddess PCS, Yara sources low-cost gas in Trinidad, and the company has also secured supply in the Middle East. This is important, because European natural gas prices have gone through the roof. I'm less familiar with other nitrogen producers' natural gas supply chains, but Fools ought to be laser-focused on this absolutely critical component.

The commodity nature of nitrogen may help explain Mosaic's (NYSE:MOS) decision to pass off its Saskferco stake to Yara this week. Mosaic is tops in phosphate, and is also pursuing more potash prowess. The company's nitrogen operations were decidedly non-core, and are a better fit for the highly integrated Yara.

Speaking of potash expansions, PCS just announced it's increasing capacity by 2.7 million metric tons. The gains are all coming from either de-bottlenecking or expanding current projects, and at a cost 60% below building a brand new mine. Production will come online faster, too. Such are the perks of excess capacity.

There are a few other global developments worth mentioning. On May 1, China raised its export duties on urea from 35% to 135%. This mirrors the country's recent curbs on the production of aluminum -- another energy-intensive product. That tariff lifted urea prices 50%, and they're moving even higher of late, at least partially on news of various delays to Middle Eastern projects.

Rounding out the week's events was Canpotex's (the Canadian potash alliance) roughly 20% price hike from current levels, to $1,000 per metric ton. The same day, Belarusian Potash, Canpotex's Eastern European analogue, kicked its latest Sri Lankan contract up to $1,050. You thought iron ore ogres Vale (NYSE:RIO) and Rio Tinto (NYSE:RTP) were having all the fun? These potash combines are wielding simply tremendous market power today.

Of the fertilizer pros mentioned, Agrium is a Fool favorite, boasting a full five-star ranking in Motley Fool CAPS. Weigh in on the firm's future with a call of your own, right here.

Fool contributor Toby Shute doesn't have a position in any company mentioned. The Motley Fool has a disclosure policy.