FarmVille is the most popular application on social-networking site Facebook, having attracted more than 56 million users worldwide since its introduction in June. And to what does FarmVille owe its popularity? Simply, it's addictive, according to comments by fans and users on forums across the web.

And First Lady Michelle Obama, the first cultivator of White House-grown fruits and vegetables since the days Eleanor Roosevelt, would likely be happy about that fact. That's because as a virtual farm, FarmVille allows users to manage and harvest crops and generally run a basic farm, as well as visit others' farms, perhaps giving participants greater insight in what it takes to run a real farm.
But as anyone who has ever tried his or her hand at the real thing, growing a tomato or two is bush league. To raise enough food to feed a household or village takes skill and dedication. And that's where the addictive quality of FarmVille really kicks in.

Known as crop mastery, participants advance through the game and are awarded mastery of all jobs in a given tier, according to Zynga Inc., developers of FarmVille and more than a dozen other Facebook game applications, or apps. There are three levels of crop mastery, each one is displayed on screen by a star next to each job showing what level of completion you have reached: bronze, silver or gold.

Mastering farming on FarmVille requires understanding of how many plots are needed for various seeds -- anything from eggplant to squash to raspberries and coffee. And once you master crops, you can then sell them at a virtual market.

The game sells "farm cash" and "farm coins" that lets players buy special items. The current FarmVille exchange rate, according to the game's site on Facebook (billed as the "farmer's best value"): $40 U.S. dollars is worth 70,600 "farm coins." Sales of such "gifts" and virtual "goods" in games such as FarmVille are set to double from last year and may hit to $1.6 billion next year, according to a study.

Cultivating and harvesting crops, however, are just one part of FarmVille's addictive quality. Participants must also buy and care for farm animals, and you can earn ribbons and bonuses just like down on the real farm. (It's a whole lot gosh darn cleaner online, however. )

To be fair, FarmVille isn't the only app of its type to provide such an agrarian thrill to Facebook users. Others include Farm Town, which has some 1.3 million users, and the highly homoerotic-sounding Barn Buddy, which is still in beta testing.

But apparently Zynga has hit a sweet spot in the American psyche for those all things agricultural. And as many Americans revisit gardening as a way to exploit thrift, FarmVille might just be one tool to help them do that -- if only in their minds.