It's a new month, so like clockwork, we get another press release from Monsanto (NYSE: MON) announcing higher guidance. The agricultural giant isn't sending out nickel-and-dime information to get free media coverage. These guidance increases are legitimate reasons to let investors know that it's doing well.

Full-Year Guidance

Low-End Increase

Jan.

$2.50 to $2.60

14%

Feb.

$2.70 to $2.80

8%

March

$3.15 to $3.25

17%

The January increase in guidance came in conjunction with Monsanto's stellar fiscal-first-quarter results, as sales in the Southern Hemisphere came in better than expected.

February's increase came in conjunction with the company's presentation at Goldman Sachs' 2008 AgForum Conference -- you've got to give the analysts something to chew on. Increased sales of RoundUp herbicides, as well as corn and soybean seed sales, caused the expected uptick in earnings.

Some of the most recent bump in guidance -- $0.23 per share, to be exact -- comes from money Monsanto receives in conjunction with its spinoff Solutia's (NYSE: SOA) emergence from bankruptcy. That's a one-time event, but there's still quite a bit of revenue growth baked into the rest of the guidance bump.

The company expects sales of both seeds and RoundUp to increase even more than previously expected. The increased global demand for RoundUp likely means that additional acres are being planted, which bodes well for DuPont (NYSE: DD), Potash (NYSE: POT), Mosaic (NYSE: MOS), and the rest of the agriculture industry.

Monsanto is now looking for full-year earnings more than 50% greater than last fiscal year's adjusted earnings. While that's great in the near term -- it's pushed Monsanto's stock up nearly 30% since last year's financials were released -- I'm not sure it can last. The company's short-term growth is tied to commodity prices. I'm not willing to call the top of the commodity bull market, but it has to end eventually ... doesn't it?

Throw on some overalls and plant your eyes on this Foolishness:

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.