When you think about it, farming and investing have quite a lot in common -- you do your research, plant your seeds, periodically pull the weeds and dust for weevils, and then hope that events out of your control don't demolish all your efforts. If it all works out, you reap the harvest, count your profits, and get ready to do it all over again.

Stretching out that analogy, Monsanto (NYSE:MON) investors might feel as if their crop just got hit by a hailstorm Wednesday morning. While this agribusiness company posted a solid third quarter, lower near-term guidance sent the stock lower by more than 6% in early trading.

For the third quarter, Monsanto posted 22% revenue growth, with 10% of that growth coming from within. Although the herbicide and productivity business was flat, the seed business was up 52% as acquisitions and strength in corn, soybeans, and cotton boosted results.

Though I certainly laud Monsanto for giving investors plenty of financial data, I think a little discussion of the cash flow statement is in order. Specifically, Monsanto described its year-to-date free cash flow as negative $838 million. The trouble is, it calculates that number in a somewhat unconventional way -- simply subtracting investing cash flow from operating cash flow.

I'll be the first to admit that free cash flow is a "fuzzy" number -- there's no hard-and-fast rule about calculating the number, and everybody has his or her own opinions on what to include and exclude. Using the closest thing to a standard approach (operating cash flow minus capital expenditures), Monsanto actually posted positive free cash flow of $489 million, up from negative $36 million for the same period last year.

On the guidance front, Monsanto management lowered expectations for the next quarter (looking for a larger loss) and lowered expectations for the next fiscal year by about 10%. More positively, management expressed confidence that earnings will grow by 20% to 25% from fiscal '06 to fiscal '07.

Today is one of those "bad hair days" that almost every stock experiences sooner or later. Although not cheap by a P/E-based methodology, a look at free cash flow and owner earnings suggests a somewhat more interesting picture.

There's no telling whether Monsanto will continue to slide to even cheaper levels, but investors interested in agribusiness and/or Monsanto specifically might want to brush up on their due diligence and see whether this guidance-induced slide presents a compelling enough buying opportunity.

For the cream of the crop on Monsanto, check out this Foolishness:

Fool contributor Stephen Simpson has no financial interest in any stocks mentioned.