Canadian fertilizer company PotashCorp has rejected a $38.49 billion bid from BHP Billiton, of Australia, to purchase the company. The fertilizer market worldwide has been a hotbed of M&A activity for the past few months and BHP Billiton’s bid for PotashCorp of Saskatchewan is just the latest in a line of deals that have been making the headlines.

On Tuesday PotashCorp said that its board had rejected the offer from BHP—saying that it undervalued the company. At $130 a share, the bid put a 16 percent premium on the company’s Monday closing share price. On news of the offer, the Canadian firm’s shares soared to $145.

The very same day the company announced that it had adopted a shareholder rights plan—or poison pill—to provide a longer timeframe for discussions in formal merger talks, in order to consider alternatives.

BHP has been focused on buying up Canadian fertilizer assets and growing its fertilizer business organically—so to speak—for some time.

This is just one of a number of deals that are in the works in the fertilizer industry. As a result of strong market performance coming out of the economic downturn—and long-term market growth due to increasing demand from emerging economies—fertilizer has been a hot commodity for quite some time.

Companies within the industry are taking advantage of their strong share prices and solid financial conditions to pick up outside assets.

Fertilizer company Agrium, for example, recently made an offer for Australian wheat exporter AWB. The Canadian company offered $1 billion for the firm—topping an existing bid by fellow Aussie firm GrainCorp.

This is Agrium’s second foray into the M&A space in recent months. The company was in a 14-month takeover battle for US rival CF Industries, which ended, unsuccessfully, in March.

And CF Industries, itself, just this month announced that it had completed the purchase of Terra Industries, of Iowa—a deal which had been in the works since January 2009. The all-stock transaction is valued at $4.7 billion.