The Earth's population tops 6.8 billion people, up from 6.1 billion a decade ago. Almost a hundred million new people arrive each year -- and all of them need to eat. But while our gloabl headcount grows, the amount of arable land does not. That disparity could spell opportunity for investors in the agriculture sector.

If you want to invest in agriculture, you'll find yourself faced with a plethora of stocks covering various aspects of this far-reaching field. The sector's more notable names include:

  • Seed and herbicide giant Monsanto (NYSE: MON) sports five-year average annual revenue growth of 13% and 40% average EPS growth. Its controversial bioengineered seeds are appealing for farmers who want to produce more with less. 
  • PotashCorp (NYSE: POT) is a major maker of fertilizer and other products. It grew briskly in recent years, only to stall as supply outpaced demand. Management now expects a reversal of that trend in the coming year or two, especially in China. BHP Billiton (NYSE: BHP) seems to share that outlook; it offered to buy the potash producer, but PotashCorp spurned its bid.
  • Mosaic (NYSE: MOS), another potash maker, is also the world's biggest phosphate producer. Some expect demand for fertilizers to soar as droughts and wildfires afflict global crops.
  • Archer-Daniels-Midland (NYSE: ADM) is a major corn and ethanol producer that stands to benefit from a growing interest in the latter as fuel. Its corn, wheat, cocoa, and oilseeds are made into foods and feed for customers worldwide. ADM commands an attractively low P/E, and boasts a growing dividend that it's been paying for roughly 35 years.
  • Tyson Foods (NYSE: TSN), long known for its poultry, is now a major beef, pork, and prepared-foods power, too. It has been aggressively cutting costs, but it may still struggle in the near future as Russia cuts back on imports of its wares.

With so many agriculture-related companies to choose from, you may have trouble deciding which stocks make the cut. The Market Vectors Agribusiness ETF (NYSE: MOO) can give you instant, diversified access to 44 stocks across the agriculture industry. Along with a cute ticker symbol, MOO, the exchange-traded fund has a decent expense ratio of 0.56% and a modest dividend yield of 1%.

The Market Vectors fund isn't the only agriculture ETF, but other agriculture-focused funds tend to sport far more holdings. Its relative concentration means the Market Vectors fund is positioned to reap stronger gains if the sector performs well. The ETF has had a volatile time in its short history, losing 51% in 2008, but surging 59% in 2009. As of Tuesday, it was down about 3% for 2010.

As the ever-expanding population of planet Earth demands its daily bread, investing in agriculture stocks could give you a great way to nourish your portfolio. 

Many compelling bargains lie beyond U.S. borders, especially in emerging markets.

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article. Motley Fool Options has recommended a synthetic long position on Monsanto, which is a Motley Fool Inside Value pick. Try any of our investing newsletter services free for 30 days. The Motley Fool is Fools writing for Fools.